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ArticleMay 24, 2018

Novel Conducting and Biodegradable Copolymers with Noncytotoxic Properties toward Embryonic Stem Cells
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Aruã C. da Silva
Aruã C. da Silva
Department of Fundamental Chemistry, Institute of Chemistry, University of São Paulo, Av. Prof. Lineu Prestes, 748, 05508-000 São Paulo, São Paulo, Brazil
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Ana Teresa S. Semeano
Ana Teresa S. Semeano
Department of Biochemistry, Institute of Chemistry, University of São Paulo, 05508-000 São Paulo, Brazil
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André H. B. Dourado
André H. B. Dourado
Department of Fundamental Chemistry, Institute of Chemistry, University of São Paulo, Av. Prof. Lineu Prestes, 748, 05508-000 São Paulo, São Paulo, Brazil
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Henning Ulrich
Henning Ulrich
Department of Biochemistry, Institute of Chemistry, University of São Paulo, 05508-000 São Paulo, Brazil
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Susana I. Cordoba de Torresi*
Susana I. Cordoba de Torresi
Department of Fundamental Chemistry, Institute of Chemistry, University of São Paulo, Av. Prof. Lineu Prestes, 748, 05508-000 São Paulo, São Paulo, Brazil
*E-mail: [email protected] (S.I.C.d.T.).
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http://orcid.org/0000-0003-3290-172X

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Cite this: ACS Omega 2018, 3, 5, 5593–5604

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https://doi.org/10.1021/acsomega.8b00510

Published May 24, 2018

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Abstract

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Electroactive biomaterials that are easily processed as scaffolds with good biocompatibility for tissue regeneration are difficult to design. Herein, the synthesis and characterization of a variety of novel electroactive, biodegradable biomaterials based on poly(3,4-ethylenedioxythiphene) copolymerized with poly(d,l lactic acid) (PEDOT-co-PDLLA) are presented. These copolymers were obtained using (2,3-dihydrothieno[3,4-b][1,4]dioxin-2-yl)methanol (EDOT-OH) as an initiator in a lactide ring-opening polymerization reaction, resulting in EDOT–PDLLA macromonomer. Conducting PEDOT-co-PDLLA copolymers (in three different proportions) were achieved by chemical copolymerization with 3,4-ethylenedioxythiophene (EDOT) monomers and persulfate oxidant. The PEDOT-co-PDLLA copolymers were structurally characterized by ¹H NMR and Fourier transform infrared spectroscopy. Cyclic voltammetry confirmed the electroactive character of the materials, and conductivity measurements were performed via electrochemical impedance spectroscopy. In vitro biodegradability was evaluated using proteinase K over 35 days, showing 29–46% (w/w) biodegradation. Noncytotoxicity was assessed by adhesion, migration, and proliferation assays using embryonic stem cells (E14.tg2a); excellent neuronal differentiation was observed. These novel electroactive and biodegradable PEDOT-co-PDLLA copolymers present surface chemistry and charge density properties that make them potentially useful as scaffold materials in different fields of applications, especially for neuronal tissue engineering.

Subjects

Introduction

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Biomaterials play a pivotal role in the field of tissue engineering (1) and have been used to induce and accelerate various phenomena, such as tissue regeneration in wound healing; (2) rapid repair of articular cartilage with very little capacity for spontaneous healing; (3) and regeneration of damaged tissues using highly porous scaffold biomaterials (4) in bones, (5,6) the cardiovascular system, (7,8) muscles, (9,10) blood vessels, (11,12) and the neuronal system. (13−15)

Stem cells are unspecialized cells with the capacity for self-renewal and pluripotency. (16) Stem cells maintain these characteristics when grown in the presence of leukemia inhibitor factor (LIF). (17) The derivation of embryonic stem cells (ESCs) from the inner cell mass of blastocyst stage embryos was first reported in 1981. (18) ESC culture in the absence of LIF leads to the spontaneous formation of suspended cell aggregates, called embryoid bodies (EBs). (19) Once adhered, the migration of cells at the periphery of EBs is stimulated. ESCs can differentiate into the cell types of all three germ layers and give rise to any mature cell of the adult organism, making them an unlimited supply for basic research and a promising therapeutic tool for regenerative medicine. (20,21) Functional differentiated cells can potentially repair or replace tissue damaged by diseases or injuries, (22) such as diabetes, heart attack, (23) Parkinson’s disease, and spinal cord injury. (24) However, protocols that allow for the better control of ESC differentiation into specific neuronal lines still require optimization. Microenvironmental mechanical properties detected by cells in contact with substrates have the ability to influence cell adhesion, migration, proliferation, and differentiation. (25,26) In recent years, there has been an increasing interest in developing materials that function as support matrices for guiding more effective cellular differentiation. These biocompatible polymeric substrates also facilitate cell transplantation because cooperation between cells is preserved, which is essential to their communication and survival. (27)

Biodegradable biomaterials are solid polymeric materials and devices that provide temporary sustentation during tissue healing procedures and enhance self-repair from injury. (28,29) Biodegradable biomaterials should not provoke sustained inflammatory or toxic responses upon implantation in the body and should have an acceptable shelf life. Their biodegradation time should match the healing or regeneration process, and furthermore, biodegradation products should be nontoxic and be metabolized and cleared from the body. Finally, biodegradable materials should have acceptable mechanical properties for the desired application. (30) In this context, biodegradable polymers based on polyesters appear to be promising candidates because of their good biocompatibility. Among these polyesters, polyglycolide, (31,32) polylactides [poly(l lactic acid) (PLLA), poly(d-lactic acid) (PDLA) or poly(d,l lactic acid) (PDLLA)], (33−35) and polycaprolactones (13,36) have been the most studied. The difference in biodegradability between PDLLA and PLLA lies in the fact that PLLA presents higher crystalline structures, which lead to lower biodegradation rates. Variations in the size and thickness of PDLLA can affect the hydrolysis rate. (37−39) Biodegradation rates can also be controlled by adjusting the molecular weight of PLA (40) or by changing the feed mole ratio of the biodegradable polymer in a copolymer composition. (41)

Electroactive biomaterials are a new generation of “smart” biomaterials based on conducting polymers (CPs). (42) Poor molecular interaction with cells is the main challenge to face for the use of CPs as biomaterials, (43) even though their biocompatibility can be highly improved by doping with specific anions (44,45) but, despite this, electroactive polymers still present low or no biodegradability. (46)

Schmidt and co-workers (47) proposed a novel biodegradable and electrical CP for biomedical applications based on a triblock polymer comprising three electroactive monomer units (polypyrrole–thiophene–polypyrrole) linked with degradable ester linkages to an aliphatic linker (4 carbons). Jing and co-workers (48) proposed a biomaterial based on a conducting and biodegradable copolymer, consisting of an aniline pentamer (AP) with a PLA triblock, called PLA-b-AP-b-PLA. Because of Jing’s approach for conducting and biodegradable copolymer biomedical application, a large number of modified copolymers have been developed, such as an electroactive star-shaped memory polymer, (49) and others mainly based on aniline oligomers, (41,50) and blends with PDLLA, (51) among others. (52−56) However, polyaniline (PANI)-based polymers still show cytotoxicity because of their conductive emeraldine forms being stable only at pH levels lower than 4, thereby limiting their use in biomedical applications. (48,57,58) In this sense, other CPs, such as those based on poly(3,4-ethylenedioxythiphene) (PEDOT), arise as an alternative for biomedical applications because they are electroactive in the whole pH range.

Concerning about the role of PEDOT among the different kinds of CPs, it has emerged as the champion material in the organic bioelectronics field, both in the biosensing domain and also for integration with living cells (both in vitro and in vivo). Also, it can be synthesized in many versatile ways, such as chemical oxidative polymerization, vapor phase polymerization, or direct electrochemical polymerization, mainly as thin film to be incorporated in a wide spectrum of devices. (59)

Recently, some works presenting different strategies to achieve PEDOT derivatives such as a (bio)functional dioxythiophene monomer (60−62) have been published. Mawad and co-workers showed a functionalized PEDOT synthesized from a modified EDOT-COOH which is possible to link with hydrophilic polymers similar to PEG to obtain PEDOT hydrogels. (63) Other interesting approach was used by Zhu and co-workers which used EDOT-OH to synthesize functionalized PEDOT copolymers, formed by EDOT-PC (functionalized with phosphorylcholine) and EDOT-MI (with maleimide), with surface chemistry mimicking cell membrane with resistance to nonspecific enzyme/cell binding and recognizing target cells specifically. (64)

The challenges for developing biomaterials for active scaffolds by electrical stimulation include (1) the difficulty of working with CPs which can only be obtained over electrodes by electrochemical synthesis; (2) to achieve surface chemistry which enables surface charge keeping biocompatibility for living cells culture; and (3) poor compatibility between conducting and biodegradable polymers. Here, we report the synthesis of a novel electroactive, biodegradable, and noncytotoxic copolymer (PEDOT-co-PDLLA) which joins the properties of both homopolymers in a single biomaterial. This is the first report of an electroactive biodegradable biomaterial based on PEDOT, offering the possibility of tuning conductivity and biodegradability by changing the composition.

Results and Discussion

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Synthesis of Conducting and Biodegradable Copolymer of PEDOT-co-PDLLA

The synthesis of PEDOT-co-PDLLA is shown in Scheme 1. The first step was the synthesis of a novel electroactive macromonomer, EDOT–PDLLA, using EDOT-OH as the initiator, and polymerizing PDLLA through a lactide ring-opening reaction catalyzed by Sn(oct)₂. This macromolecule corresponded to the biodegradable moiety of the copolymer. The second step was the formation of PEDOT-co-PDLLA at three different molar ratios, that is, 1:05, 1:25, and 1:50 PEDOT:PDLLA.

Scheme 1. (A) Synthesis of Electroactive Macromonomer EDOT–PDLLA, (B) Synthesis of Conducting and Biodegradable Copolymer PEDOT-co-PDLLA, and (C) Structural Representation of Copolymer with Charge on Conducting Backbone of PEDOT and Branched PDLLA Chains

To follow the proportion of PEDOT:PDLLA in this synthesis, ¹H nuclear magnetic resonance (NMR) analyses were performed for all prepared copolymers (see Figure S1, Supporting Information). In the EDOT–PDLLA spectrum, at 5.25 and 1.50 ppm, the corresponding multiplet signals of CH and CH₃ of the PDLLA structure are shown. Additionally, the singlet at 6.36 ppm and a group of multiplets at 3.95–4.45 ppm are likely related to EDOT bonded to PDLLA chains. By analyzing the relative intensity of the signals, the EDOT signals are much lower than the PDLLA signals because of the higher amount of lactic acid units in the polymer compared with EDOT. A signal at 2.4 ppm was also observed in the other spectra and corresponded to the residual solvent. Regarding the PEDOT-co-PDLLA spectra, a singlet observed at 4.20 ppm corresponding to the CH of EDOT monomers in the PEDOT chain confirms the formation of the copolymer. By integrating the singlet at 4.20 ppm which corresponds to 2 CH present in every EDOT unit and comparing with the multiplet centered at 5.25 ppm (corresponding to CH from PDLLA), it was possible to obtain the actual molar ratio of 1:20, 1:40, and 1:80, respectively. Even though, for the whole manuscript, the feed synthesis proportion will be maintained for indicating the different copolymers.

The infrared spectra of EDOT–PDLLA and PEDOT-co-PDLLA at three proportions are presented (Figure S1, Supporting Information). It is possible to see that the EDOT–PDLLA spectrum presents two bands at 765 and 872 cm^–1, which are diminished in the polymerized structures. For a better comprehension, DFT/PBE-D3/def2-TZV was used, and the theoretical spectrum obtained presented two bands with low intensity at 765.88 and 872 cm^–1. These vibration groups are represented in Figure 1. Moreover, Figure S2 (Supporting Information) presents vibrations in 2998–2850 and at 1756 cm^–1 for all spectra, corresponding to CH and CH₃ stretching and C═O, respectively, confirming the higher amounts of PDLLA in the structures. (65−67)

Figure 1. DFT/PBE-D3/def2-TZV optimized structures of EDOT–PDLLA macromonomers. Arrows indicate the most important contributing vibrations in the calculated band at (A) 766.88 and (B) 872 cm^–1.

Figure 1 shows two different vibrations that explain the results at the highlighted bands, in the macromonomer spectrum (see Figure S2, Supporting Information). The one at the lower wavenumber corresponds with the symmetrical bending of the H atoms vicinal to the S atom in EDOT. The other band, at higher energy, corresponds with the same asymmetrical bending. Because these vibrations were not present in the other molecules, this showed that these are the bonding sites to other monomers during the polymerization.

Other bands in the spectra must also be analyzed, that is, at 1090, 1130, 1190, 1450, 1640, and 1750 cm^–1, especially in the spectrum corresponding to the 1:25 proportion, where all of the bands are enlarged and a shoulder at 1640 cm^–1 is clearly observed. All of these vibrations are related to the PDLLA backbone and can be assigned to ρCH₂ mode (1090 cm^–1), νC–C (EDOT–PDLLA) (1130 cm^–1), τCH₂ (1190 cm^–1), and δCH₂ (1450 cm^–1); related to the C atom in PDLLA backbone vicinal to the PEDOT one. The band at 1640 cm^–1 is related to the νC═O mode of the segments located far away from the conductive backbone, whereas the band at 1750 cm^–1 can be assigned to the carbonyl group of the ester segment close to the PEDOT backbone. In the spectrum of the macromonomer EDOT–PDLLA, these bands are all sharp indicating that these vibrations do not present high degree of freedom, an indication of a more rigid structure. As already mentioned, in the spectrum corresponding to the copolymers, the bands are broad and enlarged, a consequence of higher degree of interactions of the biodegradable backbones, leading to a conformation that induces the conductive backbone to be more twisted.

Electrochemical Behavior

Cyclic voltammetry was used to investigate the electrochemical behavior of the three PEDOT-co-PDLLA copolymers with different proportions. Figure 2 shows the j/E potentiodynamic profiles of the different films deposited onto glassy carbon electrodes. The electrochemical response of a film of the macromonomer is also presented for comparison.

Figure 2. j/E potentiodynamic profiles of bare glassy carbon (black), EDOT–PDLLA (gray), and conducting biodegradable copolymer films of PEDOT-co-PDLLA 1:05 (red), 1:25 (green), and 1:50 (blue) in phosphate buffer electrolytic solution. v = 0.01 V s^–1.

Figure 2 shows the fifth voltammetric cycle of each copolymer films after stabilization in phosphoric buffer solution compared with bare vitreous carbon electrode and with a spin-coated macromonomer (EDOT–PDLLA) film. The full data with all cycles for each copolymer are shown in the Supporting Information (Figure S3). By comparing the j/E profile of the bare glassy carbon electrode with that of the macromonomer film (EDOT–PDLLA), the current generated with the macromonomer was found to be lower than that on the bare electrode, confirming the macromonomer’s insulating character. All PEDOT-co-PDLLA films in the three different proportions showed typical cyclic voltammograms as those observed for PEDOT, with oxidation peaks starting at −100 mV for the 1:50 copolymer and at 125 mV for the 1:25 and 1:05 copolymers and the corresponding reduction ones. The peaks appear very broad and not well-defined, but it is clear that the current is higher by increasing the EDOT/EDOT–PDLLA ratio in the copolymer formation.

Table 1 shows the conductivity values obtained by ac impedance measurements for different PEDOT-co-PDLLA proportions compared with other conducting and biodegradable copolymers based on aniline trimers and pentamers. (40−42,48,68) The lowest PEDOT content (1:50) had conductivity comparable with undoped aniline trimers. The intermediate PEDOT content (1:25) had a slightly higher conductivity than aniline trimers doped with CSA. The highest PEDOT content (1:05) had the highest conductivity among all conducting and biodegradable copolymers, with a value 2.5 times higher than that of the 1:25 PEDOT-co-PDLLA. These results correlated with the voltammograms obtained from PEDOT-co-PDLLA films in phosphate-buffered saline (PBS) buffer. In contrast to aniline-based copolymers, which are only highly conductive at pH lower than 2 (the main problem to be solved for their application in cell interfaces), PEDOT was stable at physiological pH values of 7.4. (48,58,68) See the Supporting Information (Figure S3).

Table 1. Conductivity of Biodegradable and Conducting Copolymers^a

	conductivity (S cm^–1)
copolymers	before doping	after doping	references
PEDOT-co-PDLLA 1:50		4.19 × 10^–8	present work
PEDOT-co-PDLLA 1:25		2.07 × 10^–5
PEDOT-co-PDLLA 1:05		5.35 × 10^–5
PUUH	0.42 × 10^–8	0.28 × 10^–6	(40)
PUUM	0.51 × 10^–8	0.77 × 10^–6
PUUL	0.55 × 10^–8	1.48 × 10^–6
PAP2		5 × 10^–6	(48)
EM PLAAP		1 × 10^–5 to 10^–6	(68)
PEA-g-TA#1		7.11 × 10^–7	(41)
PEA-g-TA#2		8.01 × 10^–6
PEA-g-TA#3		2.45 × 10^–6
polypyrrole (Ppy)		1 × 10² to 7.5 × 10³	(42)
PANI		30–200
polythiophene (PT)		10–10³
PEDOT:PSS		1–450	(69)

^{^a}

PUUL, PUUM, and PUUH: polyurethane–urea copolymerized with an aniline trimer, doped with camphorsulfonic acid (CSA); L, M, and H related to PU molecular weight. PAP2 and EM PLAAP are both PANI pentamers doped with CSA. PEA-g-TA#n: poly(ester amide) and tetraaniline grafted poly(ester amide) copolymers. PEDOT-HA/PLLA: poly (3,4-ethylenedioxythiophene) doped with hyaluronic acid/poly (l-lactic acid) composite.

The PEDOT-co-PDLLA copolymers showed conductivity ranging from 4 × 10^–8 to 5 × 10^–5 S cm^–1, as shown in the Supporting Information (Figure S4) and following conductivity equation (eq 1), comparable with other biomaterials. (40−42,48,68) These conductivity values could indicate that EDOT–PDLLA macromonomers enabled the formation of copolymers with degrees of conjugation higher than aniline trimers/pentamers. On the other hand, the loss of conjugation of the conducting backbone because of steric effects related to the twisting of the PEDOT moieties functionalized with long pending PDLLA chains cannot be ignored and will lead to very low conductivities. Table 1 shows that by doubling PEDOT proportion from 1:50 to 1:25, conductivity of PEDOT-co-PDLLA increases 10³ times. When PEDOT changes from 1:25 to 1:05, around the same proportion than before, conductivity increases just 2.5 times. Different effects must affect the bulk conductivity such as the increase in the degree of oligomerization together with a very twisted conducting backbone. It is already known for PANI that oligomers with 20 units already show conductivities similar to the polymeric chains (70) and the same conclusion was reached for PEDOT studies. (71) Therefore, in the present case, the slight increase in conductivity (2.5 times) for 1:25 to 1:05 must be related to a more important effect of the twisting of the chain. Even with an expected higher degree of oligomerization, a very coiled conformation would avoid conjugation as already known for PANI and polypyrrole. (70,72−74)

However, these macromonomers did not necessarily form extremely long chains as PEDOT itself. There are some experimental evidences that the formed structures were PEDOT oligomers with chain lengths that allow sufficient conjugation to achieve conductivity but were far from pure doped PEDOT chains. It must be remembered that during the oxidative synthesis in acetonitrile, only the soluble part is used. As pure PEDOT is not soluble in organic solvents, all solid precipitate is discarded. Some attempts were made to electropolymerize the macromonomer (74) but even that a rise in current is observed corresponding to the oxidation of EDOT–PLLA, no film is formed onto the electrode because of the formation of soluble oligomers. In other words, this strategy to produce a new electroactive and biodegradable biomaterial is very versatile and suggests that a branched copolymer with conducting moieties was obtained, as illustrated in Scheme 1.

Biodegradability Tests

The biodegradation behaviors of the three PEDOT-co-PDLLA polymers with different proportions were studied in vitro by using proteinase K, a high activity enzyme responsible for the biodegradation of polyesters. (75−77)Scheme 2 shows the chemical reactions for PEDOT-co-PDLLA copolymers and images of the PEDOT-co-PDLLA films before and after 35 days of biodegradation.

Scheme 2. (A) Biodegradation Reaction and (B) Physical Aspects of PEDOT-co-PDLLA Films before and after 35 Days of Biodegradation Assay

The biodegradation profiles of PEDOT-co-PDLLA films of different proportions are shown in Figure 3, from which it can be inferred that the lower the PDLLA content (higher PEDOT content) is, the faster the biodegradation. The biodegradation of the macromonomer EDOT–PDLLA in the same conditions and in the same period of time is also presented.

Figure 3. Biodegradation profiles of EDOT–PDLLA (black) PEDOT-co-PDLLA 1:05 (red), 1:25 (green), and 1:50 (blue) at 37 °C and 60 rpm.

The 1:05 copolymer (higher content of PEDOT) biodegrades much more rapidly than the others, whereas 1:25 and 1:50 do not present significant difference from macromonomer of EDOT–PDLLA, possibly because of the very low content of PEDOT in those copolymers. After 35 days, 1:05, 1:25, and 1:50 PEDOT-co-PDLLA copolymers reached 45.9 ± 4.1, 35.6 ± 2.0, and 29.2 ± 2.0% weight losses, respectively. Furthermore, its weight loss can be attributed to soluble components cleaved by the enzyme and water molecules (Scheme 2A), but the remaining copolymer films seem much more fragile when compared to the initial states (Scheme 2B). A few strategies for tuning biodegradation rates have included changing the number average molecular weight (M_n) of the biodegradable moiety. (40) The approach presented here employed a fixed molecular weight electroactive EDOT–PDLLA macromonomer and changed the molar ratio of EDOT–PDLLA to EDOT to obtain PEDOT-co-PDLLA copolymers with different biodegradation rates.

Table 2. Biodegradation of Conducting and Biodegradable Copolymers and Composites^a

biomaterials	time scale (days)	biodegradation (%)	references
PEDOT-co-PDLLA 1:05	0–35	46	present work
PEDOT-co-PDLLA 1:25		36
PEDOT-co-PDLLA 1:50		29
PUUL	0–30	100	(40)
PUUM		50
PUUH		10
PH10	0–5	100	(49)
PH20		80
PH40		60
PH10AT		40
PEA	0–6	45	(41)
PEA-g-TA#1		40
PEA-g-TA#2		35
PEA-g-TA#3		25
10% PEDOT-HA/PLLA	0–56	8	(65)
30% PEDOT-HA/PLLA		9
50% PEDOT-HA/PLLA		11

^{^a}

PUUL, PUUM, and PUUH: polyurethane–urea copolymerized with an aniline trimer; L, M, and H related to PU molecular weight. PH10, PH20, PH40, and PH10AT: star-shaped polylactide and aniline-trimer-based materials. PEA and PEA-g-TA#n: poly(ester amide) and tetraaniline grafted poly(ester amide) copolymers. PEDOT-HA/PLLA: poly (3,4-ethylenedioxythiophene) doped with hyaluronic acid/poly (l-lactic acid) composite.

Compared with recently synthesized conducting and biodegradable copolymers presented in the literature (Table 2), the PEDOT-co-PDLLA copolymers displayed an acceptable range of time for biodegradation. Although our approach resulted in branched copolymers, their biodegradability behavior was closer to those obtained for aniline trimers and pentamers in block copolymers, (40,41,56) which biodegrade much more rapidly than PEDOT-HA/PLLA composites. (65) This provided strong evidence that the conducting moiety of PEDOT is composed of oligomers long enough to present electroactivity and conductivity but could be suitable for biomedical applications. These copolymers are readily consumed by macrophages during the normal wound healing response, thereby reducing the chances for long-term adverse effects. (47,78)

Water Contact Angle of PEDOT-co-PDLLA Films

The wettability of the different PEDOT-co-PDLLA copolymers were analyzed, and the results are listed in Table 3. It can be seen that the higher PDLLA content in the copolymer is, the lower the water contact angle. A polystyrene plate dish functionalized for cell culture was used as a control and had a contact angle of 28° ± 3°. The contact angle of the macromonomer EDOT–PDLLA was also measured for comparison showing a more hydrophilic character than all of the copolymers.

Table 3. Water Contact Angle of Three Copolymers of PEDOT-co-PDLLA and Control

	contact angle (deg)
control	28 ± 3
PEDOT-co-PDLLA 1:05	64 ± 3
PEDOT-co-PDLLA 1:25	58 ± 1
PEDOT-co-PDLLA 1:50	51 ± 3
EDOT–PDLLA	47 ± 1

Cytotoxicity

Biocompatible polymers have been used to replace parts of living systems or to provide intimate contact with living tissues. To investigate the potential biocompatibility of the PEDOT-co-PDLLA copolymers with biological systems, cytotoxic assays were performed with E14.tg2a ESCs using trypan blue exclusion dye (Figure 4), as were adhesion and migration assays using neural precursor cells (NPCs) sourced from predifferentiated ESCs induced by embryoid body (EB) suspension cultures (Figure 5).

Figure 4. Proliferation and viability of ESCs on PEDOT-co-PDLLA CPs. Polymeric substrates with different compositions were tested against the control (traditional polystyrene plate), on which the cells were cultured for 24 h. (A) Optical microscopy images, calibration bar: 400 μm; (B) total count of cells grown on the polymer substrates; (C) percentage of viable cells shown as mean values ± SD; *P < 0.05.

Figure 5. Adhesion and migration of NPCs from EBs on PEDOT-co-PDLLA CPs. Polymeric substrates for cell culture with different compositions were tested against the commercial plastic dish (control), to which the EBs adhered and the peripheral cells migrated. (A) Phase-contrast optical microscopy representative images of the EBs after 24 h of culture, with a calibration bar corresponding to 200 μm; (B) numbers of EBs adhered to the respective polymeric substrates; (C) mean ratio of the migration halo normalized by the respective area of each EB. Data are reported as mean values ± SD; *P < 0.05, **P < 0.01.

Cell viability assays showed a slight decrease in proliferation of the cells grown on PEDOT-co-PDLLA-based polymers within the first 24 h. However, this decrease was only significant for the PEDOT:PDLLA 1:25 composition, in which a more irregular dispersion of particles occurred, possibly because of a decreased solubility. Cell viability tended to decrease by approximately 10% when cells were cultured on the copolymers compared with controls. However, this reduction was not significant for any composition.

In the absence of LIF, ESCs formed three-dimensional aggregates called EBs, which recapitulate early mammalian embryogenesis with spontaneous cell differentiation and generation of precursor cells of the three germ layers. (19) To form EBs, undifferentiated ESCs were cultured in nonadherent Petri dishes, and neuronal differentiation was induced by retinoic acid. After this stage, EBs preferentially gave rise to mature neural cells as neurons and glial cells. EBs were plated on traditional plastic plates and on PEDOT-co-PDLLA-based polymers with PEDOT:PDLLA proportions of 1:50, 1:25, and 1:05. EBs that had adhered on the substrates were counted, and cell migration halos from the EBs were measured with ImageJ software for a minimum of 30 EBs per condition (Figure 5). Good adhesion of the EBs on the copolymers was observed; however, suitable PEDOT levels in the cell support matrix composition bring together favorable properties for adhesion of EBs, whereas higher amounts of PEDOT (i.e., composition 1:5) tended to inhibit cell adhesion and delayed cellular migration within the first 24 h. A significant decrease in the mean migration halo of adhered EBs on the PEDOT-co-PDLLA substrates (1:25 and 1:05) was observed compared to the controls.

The cells were induced to neuronal differentiation and assayed after 7 and 14 days. Cell morphologies after 7 days of differentiation are shown in Figure 6, and the expression patterns of neuron-specific immunomarkers are shown in Figure 7. During the differentiation progress, cells expand more on the conductive polymers than on traditional plastic, exhibiting an elongated shape with more extensive neurites.

Figure 6. Phase contrast microscopy images of ESCs after 7 days of neural differentiation on PEDOT-based scaffolds. Scale bar: 400 μm.

Figure 7. Characterization of E14.tg2a ESC neural differentiation on a commercial plastic plate (control) and on PEDOT:PDLLA conductive polymers at proportions of 1:50, 1:25, and 1:05. Immunostaining for young neurons with anti-βIII tubulin (red) after 7 days from the beginning of the neural differentiation process. Immunostaining for mature neurons with anti-MAP2 (green) and glial cells with anti-S100β (red) after 14 days. Cell nuclei were stained with DAPI (blue). Scale bar: 100 μm.

The cells were fixed and immunostained on days 7 and 14 of the differentiation process. Immunofluorescence assays (Figures 7 and 8) showed that neuronal differentiation was enhanced by PEDOT-co-PDLLA coatings.

Figure 8. Quantification of neuronal-differentiated ESCs following anti-MAP-2 staining by StrataQuest analysis software (TissueGnostics). Images of phase-contrast and DAPI and Alexa488 fluorescent channels were overlaid (column 1); migration halo analysis by combining and processing images of DAPI and phase-contrast ROI (column 2); measurement of the total lengths of anti-MAP2-tagged neurites (column 3).

Following 7 days of induction to neural differentiation, immunostaining for βIII-tubulin, indicative of young neurons, was observed (Figure 7, first column in red). Cells cultured on conductive polymers showed higher βIII-tubulin staining and more neurite outgrowth compared to the control cell culture substrate, suggesting that the nature and surface charge density provided by the new polymeric substrates were crucial for neuronal differentiation and orientation of neuronal extensions. After 14 days of differentiation, a visible increase occurred in immunostaining for microtubule-associated protein-2 (MAP2) expression, characteristic for mature neurons (Figure 7, third column in green). This increase in MAP2 immunostaining was especially observed for the PEDOT:PDLLA 1:50 polymer, suggesting that PEDOT-co-PDLLA polymers promote the maturation of neurons together with neurite outgrowth, improving the complexity of the neural network. As further seen in Figure 7 in the control experiment, fewer mature neurons (MAP2-positive cells) and higher staining intensity of glial cells (anti-S100β-positive cells) were observed. This suggested that neurogenesis was favored by PEDOT-co-PDLLA polymer substrates.

A quantitative analysis of fluorescence images of DAPI (cell nuclei)- and MAP2-positive neural progenitor cells with Alexa 488 secondary antibody was performed using StrataQuest analysis software (TissueGnostics; Figure 8). The migration area of the cells surrounding the EBs and the total length of the neurofilaments were much larger when these agglomerated cells had adhered to the PEDOT-co-PDLLA matrices. The 1:50 copolymer showed the best performance in the cell culture and differentiation of neural progenitor cells, with 24 257 μm migration halos and 13 885 μm neurofilament lengths. These values represented increases of 65 and 370%, respectively, compared with controls.

Discussion

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Biological effects including cell adhesion, migration, and biocompatibility of a scaffold are essential for its applications in tissue engineering. Cell attachment is a crucial prerequisite for biological applications because when NPCs attached onto a scaffold under appropriate conditions, they proliferate and differentiate into different cell types.

Surface charge density promotes electrostatic interactions between the scaffold and the anchoring proteins of cells that trigger cell signaling that models cell spreading, migration, and differentiation. The orientation and adsorption rate of serum proteins in the substrate is also affected by their surface charge, interfering in the activation of integrins that feel the surrounding environment. (79)

In this context, Saltó and co-workers (80) examined whether it is possible to modulate the attachment of neural stem cells onto oxidized and reduced PEDOT/tosylate surfaces, and its results show that oxidized PEDOT increased (and reduced PEDOT decreased) the adhesion of two different types of neural stem cells. They explained that effects related to PEDOT surface in different oxidation states could dictate the orientation of proteins, hence controlling the stem cell adhesion and density. In other words, high contents of adsorbed proteins are not favorable for optimal adhesion for the two stem cell systems but rather their orientation. A dense protein layer (observed on reduced surface of PEDOT) that is tightly bound may prevent the formation of an ideal extracellular matrix onto the substrate that allows optimal interaction with cells.

Furthermore, Svennersten and co-workers (44) proposed a model to explain different effects of reduced and oxidized surfaces on cell adhesion and viability of MDCK cells on PEDOT/tosylate surface. Onto reduced surface (negative charged), fibronectin linked in an optimal structure with RGD-domains readily to bind to α_νβ₃ integrin, confirming that hypothesis that protein orientation plays an important role in the adhesion process. Also, they mentioned that in terms of surface chemistry, groups as −OH, −COOH, and −NH₂ can bind to α₅β₁ integrin, whereas α_νβ₃ integrin is more specific in binding to −COOH.

Because the chemical composition, stiffness, wettability, topographical, and electrical properties of the substrates can affect the biological effect of the biomaterial, it becomes difficult to identify specifically its origin; (81,82) fortunately, the comparison experiment offers some clues:

Compared with commercial polystyrene, PDLLA-based copolymers present the advantage of containing −COOH and −OH groups that improve the surface chemistry for interaction with components of the cell membrane. Besides that, during PEDOT-co-PDLLA synthesis, the oxidation of PEDOT with persulfate leads to positive-charged chains of PEDOT doped with SO₄^2– as counter-ions. Charge density increases proportionally with the PEDOT content from 1:50 to 1:05.

The nature of a charge density in CP electrodes, in analogy to that created by well-defined Helmholtz layers on metal electrodes, has to our knowledge never been described, which makes it even more complicated to understand the interface of CPs with cell culture. Because positive-charged PEDOT chains are in contact with water, proteins, and different ions in the culture media, it is possible to state that ions exchanged to counter-balance charges in PEDOT chains in a dynamic equilibrium process simultaneously with proteins adsorbing to form an adherent monolayer. This adsorption process is dominated by an entropic gain by releasing the otherwise low-entropy water that is near the interface. (83,84) Moreover, it is not well-understood if charges on the surface or electric fields generated by the motion of ions close to the interface have direct influence on cell processes such as adhesion, migration, and differentiation. However, it is well-known that cell membrane is constituted by phosphatidylserine which induced a negative charge and plays an important role in electrostatic interactions. (85) In addition, neuronal cells have negative potential in terms of balance of ions inside and outside cells, (86) and it has been widely studied in the role of electric field and stimulation on controlling ions signaling for neuronal cells. (87,88)

Undifferentiated ESCs require plasma-treated cell culture polystyrene which provides a negative charge on plastic surface encouraging cell attachment. Higher growth of ESC colonies was observed for control, followed by copolymers with the best dispersion of PEDOT, suggesting that the presence of positive charges is critical for attachment and proliferation of stem cells, in agreement with Saltó and co-workers. (80)

Surface properties as wettability and roughness play a very important role in modelling cellular adhesion. Adhesion of human fetal osteoblastic cells was enhanced on PLLA with 5 nm R_q compared to polystyrene substrates with 3.84 nm, (89) bringing evidence that the differences of nanotopography of the concerned polymers can affect these cellular processes on other cell models as neural cells.

The water contact angles of the reduced and oxidized states of PEDOT/tosylate electrode (44) are 30° ± 5° and 58° ± 6°, respectively, that are similar with contact angles of polystyrene surface (28° ± 3°) and oxidized PEDOT-co-PDLLA (51° to 64° dependent of PEDOT content), which suggests to be also a condition to favor the growth of neural cells on the copolymer against the control.

No obvious cytotoxicity of PEDOT-co-PDLLA could be observed for neural stem cells. The good performance of PEDOT-co-PDLLA is consistent with the previous studies of films based on both PDLLA and PEDOT which exhibited friendly interaction with neural cells. Traditional tissue cultured polystyrene plates have no charge, and data show that 7 days after retinoic acid removal and FGF and N₂ addition, the staining revealed an overall difference in βIII-tubulin positive cells which is increased when the cells are grown on PEDOT-co-PDLLA. Apart from excellent noncytotoxicity, it is remarkable that PEDOT-co-PDLLA can enhance the ESCs differentiation toward astrocytes and especially neurons. Charge and surface chemistry are key points to the improved differentiation processes.

Conclusions

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The design of stimuli–response copolymers is an important developing research area of biomaterials. Such novel biomaterials should provide an optimal environment for the in vitro growth and development of cells. Herein, PEDOT-co-PDLLA copolymers were synthesized and presented excellent electroactivity with a wide conductivity range depending on the PEDOT content. The presence of PDLLA segments offered the copolymers biodegradability, which should be ideal for biomedical applications. In vitro cell experiments with ESCs showed that the PEDOT-co-PDLLA substrates were noncytotoxic and enhanced the differentiation process to neural cells. Migration halos and neurofilament lengths were increased in 65 and 370%, respectively, compared with controls, for copolymers containing 1:50 PEDOT:PDLLA; this proportion presents increased hydrophilicity and lower conductivity when compared to other copolymers with higher amount of PEDOT. As discussed, charge and surface chemistry are key points for the understanding of the mechanism of the differentiation processes. These fabricated PEDOT-co-PDLLA copolymers can serve as novel electroactive, biodegradable, and biocompatible materials potentially useful in different applications.

Experimental Section

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Materials

(2,3-Dihydrothieno[3,4-b][1,4]dioxin-2-yl)methanol (EDOT-OH) and 3,6-dimethyl-1,4-dioxane-2,5-dione (lactide) were purchased from Sigma-Aldrich. Organometallic catalyst tin(II)-2-ethylhexanoate (Sn(oct)₂) was obtained from Sigma-Aldrich. Toluene (99.5%), acetonitrile (99.5%), hexane (98.5%) chloroform (99.5%), and methanol (99.5%) were purchased from Synth and were distilled before use.

Chemical Synthesis of Conducting and Biodegradable Copolymers PEDOT-co-PDLLA

The first step of synthesis was to obtain an electroactive macromonomer of EDOT–PDLLA. 3,6-Dimethyl-1,4-dioxane-2,5-dione (2.76 g, 20 mmol), hydroxymethyl EDOT (100 mg, 0.6 mmol), and tin(II)-2-ethylhexanoate (0.016 mL, 0.05 mmol) were stirred at 110 °C with 7 mL of toluene for 24 h. The solvent was removed by distillation under reduced pressure (20 mBar, 60 °C). The obtained solid product was purified by recrystallization with a (1:4) hexane/methanol mixture, separated by decantation and vacuum dried until constant mass. The yield obtained from this procedure was 98%.

¹H NMR (500 MHz, CDCl₃-d): δ 1.48–1.83 (m, 3H, H^h), 3.80–3.90 (m, 2H, H^e), 4.07–4.13 (m, 1H, H^d), 4.21–4.28 (m, 2H, H^c), 5.00–5.30 (m, 1H, H^g), 6.35 (s, 2H, H^a) ppm.

¹³C NMR (500 MHz, CDCl₃-d): δ 16.7 (C^h), 66.7 (C^c), 69.0 (C^g), 69.2 (C^e), 72.5 (C^d), 116.4 (C^a), 129.0 (C^b) 169.4 (C^f) ppm.

The second step is composed of obtaining the conducting and biodegradable copolymer of PEDOT-co-PDLLA. For this, 2.7 g of the macromonomer of EDOT–PDLLA was dissolved in 17.5 mL of dried acetonitrile and kept under magnetic stirring at 30 °C for 2 h. Subsequently, 3,4-ethylenedioxythiphene (EDOT) (0.06 g, 0.42 mmol; 0.12 g, 0.81 mmol; and 0.60 g, 4.20 mmol) and NH₄S₂O₈ (0.18 g, 0.8 mmol; 0.36 g, 1.62 mmol; and 1.80 g, 8.0 mmol) were added to the reaction vessel to obtain the proportions of 1:50, 1:25, and 1:05 of PEDOT:PDLLA, respectively, and kept under magnetic stirring at 30 °C for 24 h. After the reaction medium changed to dark blue, only the soluble fraction was placed in another glass vessel and the solvent was removed by distillation under reduced pressure (20 mBar, 60 °C), and the resultant solid obtained was PEDOT-co-PDLLA. Scheme 1 shows the structure and a representative illustration of PEDOT-co-PDLLA, as analyzed by ¹H and ¹³C NMR spectroscopy.

¹H NMR (500 MHz, CDCl₃-d): δ 1.48–1.83 (m, 3H, H^h), 3.80–3.90 (m, 2H, H^e), 4.07–4.13 (m, 1H, H^d), 4.20 (s, 2H, CH₂ofthiophenes, H^j), 4.21–4.28 (m, 2H, H^c), 5.00–5.30 (m, 1H, H^g), 6.32 (s, 2H, H^a) ppm.

¹³C NMR (500 MHz, CDCl₃-d): δ 16.7 (C^h), 66.7 (C^c), 69.0 (C^g), 69.2 (C^e), 72.5 (C^d), 99.0 (C-thiophene, C^j), 116.4 (C^a), 129.0 (C^b) 169.4 (C^f) ppm.

Instrumentation

¹H and ¹³C spectra were recorded on a Bruker AIII 500 MHz spectrometer at 500 and 125 MHz, respectively. Chloroform-d (CDCl₃) was used as a solvent, and tetramethylsilane served as an internal standard.

Infrared spectra were obtained with a Frontier Fourier transform infrared spectrometer (PerkinElmer) with an attenuated total reflection accessory. The spectra were captured in the 4000–600 cm^–1 range, and an average of 32 scans was taken at a resolution of 4 cm^–1.

Electrochemical experiments were performed using a multipotentiostat Autolab M101 (Metrohm), controlled by NOVA 1.11 software. All experiments were performed using a platinum sheet and Ag/AgCl/Cl^–_(sat) as counter and reference electrodes, respectively.

For electrochemical experiments, EDOT–PDLLA or PEDOT-co-PDLLA copolymer thin films were deposited onto glassy carbon electrodes; while for cell culture experiments, indium tin oxide (ITO)-coated glasses were used as substrates. Moreover, 20 mg/mL solutions of each copolymer or macromonomer in chloroform were prepared; then, 200 μL of each solution was slowly casted on the substrate (either glassy carbon electrode or ITO) by using an Ossila spin-coater under constant 3000 rpm rotation.

The conductivity of the copolymer films was measured by placing the copolymer films between two identical gold electrodes (diameter of 1 cm) and using a multipotentiostat Autolab M101 (Metrohm). The ac impedance was measured over a 0.01 to 10⁵ Hz frequency range and an amplitude of 10 mV. The conductivity was calculated using eq 1 (90)

(1)

where σ is the conductivity in S cm^–1, R is the Ohmic resistance of the copolymer, l is the distance between the two electrodes, and A is the area of the electrodes.

For biodegradation tests, a traditional procedure was employed. (76,77) The PEDOT-co-PDLLA copolymer films were placed in a vial 2 cm in diameter. Phosphate buffer solution was prepared at pH 7.4 and 37 °C. Each vial with copolymer film was weighed, and 5 mL of PBS, 1 mg of proteinase K, and 0.5 mg of chloramphenicol were added. The vials were placed in a 37 °C shaker at a rotating speed of 60 rpm. The buffer and proteinase K solution were replaced every 24 h to maintain the activity. Copolymer films were withdrawn every 7 days and washed twice with deionized water. Films were dried in an oven at 50 °C overnight and vacuum-dried for 2 days to remove moisture. Dry specimens were weighed, and the mass loss was calculated by the following equation

(2)

Static water contact angle measurements were used to evaluate the surface hydrophilicity of the PEDOT-co-PDLLA copolymers at different proportions. A drop of Milli-Q water was placed onto the surface of the sample, and a picture of the water drop was taken by a PixeLINK digital camera, coupled with Nikon optics. The images were then analyzed with ImageJ software to obtain the contact angle. The average of five measurements at different positions on the film was taken to calculate the contact angle.

In Silico Structure Optimization

The macromonomer structure was optimized by DFT calculations with ORCA 3.0.3 (91) using the PBE functional (92) and atomic basis set Ahlrichs-def2-TZV, (93,94) and to consider dispersion effects, Grimme’s dispersion (D3) with the Becke–Johnson damping parameter (95) was used. Hereafter, this process is named DFT/PBE-D3/def2-TZV. EDOT bonded to three units of an LA chain was used as a monomer model.

Cell Culture and Differentiation

Undifferentiated E14.tg2a mouse ESCs were cultured in high glucose Dulbecco’s modified Eagle’s medium (DMEM), supplemented with 1% nonessential amino acids (NEAA), 15% ESCs qualified fetal bovine serum (FBS), 7 μg/mL leukemia inhibitory factor (LIF), 100 U/mL penicillin, and 0.1 mg/mL streptomycin. EBs were formed in suspension by culturing 5 × 10⁶ cells in nonadherent plates in high glucose DMEM medium without LIF and with 1% NEAA and 20% FBS for 2 days, followed by 4 days of neural differentiation induction by 2 μM retinoic acid, changing the medium every 2 days. The EBs were plated on polymer scaffolds in DMEM/F12 (1:1) medium supplemented with 20 ng/mL basic fibroblast growth factor and 1% Bottenstein’s N-2 formulation to induce neuronal differentiation during 14 days. Incubation was carried under 5% CO₂ and 95% humidity at 37 °C.

Cell Viability Assay

To investigate the biocompatibility of the polymeric scaffolds with different compositions, E14.tg2a cells were seeded at a density of 1 × 10⁵/cm² onto traditional polystyrene plates or onto copolymers films with proportions of 1:50, 1:25, and 1:05 of PEDOT:PDLLA deposited on ITO glass substrates. After 24 h, ES colonies were detached using TrypLE Express and dissociated into single cells. Dead cells were stained with 0.08% trypan blue dye mixed with cell suspension (1:1). Cell viability was determined by counting stained and unstained cells with a Neubauer chamber on an inverted microscope.

Embryoid Body Attachment and Cell Migration Assay

Cell adhesion was evaluated by the number of EBs able to attach onto the polymeric substrates. After formation and neural induction, 30 EBs were plated onto traditional plastic surfaces or PEDOT-co-PDLLA-based scaffolds with increasing concentrations of PEDOT. Cells were incubated at ideal conditions for 24 h. Then, the medium with unattached EBs was changed. EBs adhered onto the polymeric surfaces were counted. To measure cell migration from the EBs, images were recorded after 48 h, and migration halos were analyzed and quantified with StrataQuest software (TissueGnostics). This imaging analysis program analyzed data obtained from tissue or cell culture slides using a workflow similar to that of flow cytometry. Gating procedures were used to determine cell populations positive or negative for epitope expression of interest. DAPI fluorescence was used as a master channel for cell quantification. Images of phase-contrast and DAPI and MAP2-staining Alexa488 fluorescence channels were overlapped. Migration halo analysis was performed by combining and processing the images of DAPI and phase-contrast ROI. Total length measurements of anti-MAP2-tagged neurites were performed.

Immunofluorescence Staining Assay

Differentiated cells were fixed with 4% paraformaldehyde in PBS for 30 min at room temperature, followed by three washes with PBS. The cells were incubated with blocking solution (0.05% Triton X-100 and 4% FBS in PBS) for 1 h and subsequently incubated with primary antibody overnight at 4 °C. The next day, PBS washes were followed by incubation with secondary antibody for 2 h at room temperature in the dark. The primary antibodies used and their dilutions were β3-tubulin and MAP2 (1:200). Alexa488 anti-rabbit and anti-mouse antibodies (1:1000) were used as secondary antibodies. The coverslips were washed three times with PBS and incubated for counterstaining with 4′,6-diamidino-2-phenyllindole (DAPI). DAPI was used as the master channel to identify nuclei.

Supporting Information

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The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acsomega.8b00510.

¹H NMR spectra, infrared spectra, j/E potentiodynamic profiles with all five cycles, and Nyquist plots of impedance spectroscopy for PEDOT-co-PDLLA 1:05, 1:25, and 1:50, respectively (PDF)

ao8b00510_si_001.pdf (439.95 kb)

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Author Information

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Corresponding Author
- Susana I. Cordoba de Torresi - Department of Fundamental Chemistry, Institute of Chemistry, University of São Paulo, Av. Prof. Lineu Prestes, 748, 05508-000 São Paulo, São Paulo, Brazil; http://orcid.org/0000-0003-3290-172X; Email: [email protected]
Authors
- Aruã C. da Silva - Department of Fundamental Chemistry, Institute of Chemistry, University of São Paulo, Av. Prof. Lineu Prestes, 748, 05508-000 São Paulo, São Paulo, Brazil
- Ana Teresa S. Semeano - Department of Biochemistry, Institute of Chemistry, University of São Paulo, 05508-000 São Paulo, Brazil
- André H. B. Dourado - Department of Fundamental Chemistry, Institute of Chemistry, University of São Paulo, Av. Prof. Lineu Prestes, 748, 05508-000 São Paulo, São Paulo, Brazil
- Henning Ulrich - Department of Biochemistry, Institute of Chemistry, University of São Paulo, 05508-000 São Paulo, Brazil
Notes
The authors declare no competing financial interest.

Acknowledgments

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We gratefully acknowledge Brazilian agencies (São Paulo Research Foundation FAPESP, Proc. 2015/26308-7, and 2012/50880-4; National Council for Scientific and Technological Development, CNPq; and Coordination of Improvement of Higher Level Personnel, CAPES) for their financial support. A.C.d.S. and A.H.B.D. thank FAPESP (Proc. 2014/09353-6 and 2013/25592-8) for scholarships. A.T.S.S. is grateful for a CAPES graduate studies fellowship.

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Heydarkhan-Hagvall, Sepideh; Schenke-Layland, Katja; Dhanasopon, Andrew P.; Rofail, Fady; Smith, Hunter; Wu, Benjamin M.; Shemin, Richard; Beygui, Ramin E.; MacLellan, William R.
Biomaterials (2008), 29 (19), 2907-2914CODEN: BIMADU; ISSN:0142-9612. (Elsevier Ltd.)
Electrospinning using natural proteins or synthetic polymers is a promising technique for the fabrication of fibrous scaffolds for various tissue engineering applications. However, one limitation of scaffolds electrospun from natural proteins is the need to crosslink with glutaraldehyde for stability, which has been postulated to lead to many complications in vivo including graft failure. In this study, the authors detd. the characteristics of hybrid scaffolds composed of natural proteins including collagen and elastin, as well as gelatin, and the synthetic polymer poly(ε-caprolactone) (PCL), so to avoid chem. crosslinking. Fiber size increased proportionally with increasing protein and polymer concns., whereas pore size decreased. Electrospun gelatin/PCL scaffolds showed a higher tensile strength when compared to collagen/elastin/PCL constructs. To det. the effects of pore size on cell attachment and migration, both hybrid scaffolds were seeded with adipose-derived stem cells. SEM and nuclei staining of cell-seeded scaffolds demonstrated the complete cell attachment to the surfaces of both hybrid scaffolds, although cell migration into the scaffold was predominantly seen in the gelatin/PCL hybrid. The combination of natural proteins and synthetic polymers to create electrospun fibrous structures resulted in scaffolds with favorable mech. and biol. properties.
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Balguid, A.; Mol, A.; van Marion, M. H.; Bank, R. A.; Bouten, C. V. C.; Baaijens, F. P. T. Tailoring Fiber Diameter in Electrospun Poly(ε-Caprolactone) Scaffolds for Optimal Cellular Infiltration in Cardiovascular Tissue Engineering. Tissue Eng., Part A 2009, 15, 437– 444, DOI: 10.1089/ten.tea.2007.0294
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Tailoring Fiber Diameter in Electrospun Poly(.vepsiln.-Caprolactone) Scaffolds for Optimal Cellular Infiltration in Cardiovascular Tissue Engineering
Balguid, Angelique; Mol, Anita; van Marion, Mieke H.; Bank, Ruud A.; Bouten, Carlijn V. C.; Baaijens, Frank P. T.
Tissue Engineering, Part A (2009), 15 (2), 437-444CODEN: TEPAB9; ISSN:1937-3341. (Mary Ann Liebert, Inc.)
Despite the attractive features of nanofibrous scaffolds for cell attachment in tissue-engineering (TE) applications, impeded cell ingrowth has been reported in electrospun scaffolds. Previous findings have shown that the scaffold can function as a sieve, keeping cells on the scaffold surface, and that cell migration into the scaffold does not occur in time. Because fiber diam. is directly related to the pore size of an electrospun scaffold, the objective of this study was to systematically evaluate how cell delivery can be optimized by tailoring the fiber diam. of electrospun poly(.vepsiln.-caprolactone) (PCL) scaffolds. Five groups of electrospun PCL scaffolds with increasing av. fiber diams. (3.4-12.1 μm) were seeded with human venous myofibroblasts. Cell distribution was analyzed after 3 days of culture. Cell penetration increased proportionally with increasing fiber diam. Unobstructed delivery of cells was obsd. exclusively in the scaffold with the largest fiber diam. (12.1 μm). This scaffold was subsequently evaluated in a 4-wk TE expt. and compared with a poly(glycolic acid)-poly(4-hydroxybutyrate) scaffold, a std. scaffold used successfully in cardiovascular tissue engineering applications. The PCL constructs showed homogeneous tissue formation and sufficient matrix deposition. In conclusion, fiber diam. is a crucial parameter to allow for homogeneous cell delivery in electrospun scaffolds. The optimal electrospun scaffold geometry, however, is not generic and should be adjusted to cell size.
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Riboldi, S. A.; Sampaolesi, M.; Neuenschwander, P.; Cossu, G.; Mantero, S. Electrospun Degradable Polyesterurethane Membranes: Potential Scaffolds for Skeletal Muscle Tissue Engineering. Biomaterials 2005, 26, 4606– 4615, DOI: 10.1016/j.biomaterials.2004.11.035
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Electrospun degradable polyesterurethane membranes: potential scaffolds for skeletal muscle tissue engineering
Riboldi, Stefania A.; Sampaolesi, Maurilio; Neuenschwander, Peter; Cossu, Giulio; Mantero, Sara
Biomaterials (2005), 26 (22), 4606-4615CODEN: BIMADU; ISSN:0142-9612. (Elsevier Ltd.)
Skeletal muscle tissue engineering represents an attractive approach to overcome problems assocd. with autologous transfer of muscle tissue and provides a valid alternative in muscle regeneration enhancement. The aim of this study was to investigate the suitability, as scaffold for skeletal muscle tissue engineering, of a known biodegradable block copolymer (DegraPol) processed by electrospinning in the novel form of microfibrous membranes. Scaffolds were characterized with ref. to their morphol., degradative and mech. properties. Subsequently, cell viability, adhesion and differentiation on coated and uncoated DegraPol slides were investigated using line cells (C2C12 and L6) and primary human satellite cells (HSCs). The membranes exhibited absence of toxic residuals and satisfactory mech. properties (linear elastic behavior up to 10% deformation, E modulus in the order of magnitude of MPa). A promising cellular response was also found in preliminary expts.: both line cells and HSCs adhered, proliferated and fused on differently coated electrospun membranes. Pos. staining for myosin heavy chain expression indicated that differentiation of C2C12 multinucleated cells occurred within the porous elastomeric substrate. Together the results of this study provide significant evidence of the suitability of electrospun DegraPol membranes as scaffolds for skeletal muscle tissue engineering and that they represent a promising alternative to scaffolds currently used in this field.
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Kim, B.-S.; Nikolovski, J.; Bonadio, J.; Smiley, E.; Mooney, D. J. Engineered Smooth Muscle Tissues: Regulating Cell Phenotype with the Scaffold. Exp. Cell Res. 1999, 251, 318– 328, DOI: 10.1006/excr.1999.4595
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Engineered Smooth Muscle Tissues: Regulating Cell Phenotype with the Scaffold
Kim, Byung-Soo; Nikolovski, Janeta; Bonadio, Jeffrey; Smiley, Elizabeth; Mooney, David J.
Experimental Cell Research (1999), 251 (2), 318-328CODEN: ECREAL; ISSN:0014-4827. (Academic Press)
Culturing cells on three-dimensional, biodegradable scaffolds may create tissues suitable either for reconstructive surgery applications or as novel in vitro model systems. In this study, we have tested the hypothesis that the phenotype of smooth muscle cells (SMCs) in three-dimensional, engineered tissues is regulated by the chem. of the scaffold material. Specifically, we have directly compared cell growth and patterns of extracellular matrix (ECM) (e.g., elastin and collagen) gene expression on two types of synthetic polymer scaffolds and type I collagen scaffolds. The growth rates of SMCs on the synthetic polymer scaffolds were significantly higher than on type I collagen sponges. The rate of elastin prodn. by SMCs on polyglycolic acid (PGA) scaffolds was 3.5 ± 1.1-fold higher than that on type I collagen sponges on Day 11 of culture. In contrast, the collagen prodn. rate on type I collagen sponges was 3.3 ± 1.1-fold higher than that on PGA scaffolds. This scaffold-dependent switching between elastin and collagen gene expression was confirmed by Northern blot anal. The finding that the scaffold chem. regulates the phenotype of SMCs independent of the scaffold phys. form was confirmed by culturing SMCs on two-dimensional films of the scaffold materials. It is likely that cells adhere to these scaffolds via different ligands, as the major protein adsorbed from the serum onto synthetic polymers was vitronectin, whereas fibronectin and vitronectin were present at high d. on type I collagen sponges. In summary, this study demonstrates that three-dimensional smooth muscle-like tissues can be created by culturing SMCs on three-dimensional scaffolds, and that the phenotype of the SMCs is strongly regulated by the scaffold chem. These engineered tissues provide novel, three-dimensional models to study cellular interaction with ECM in vitro. (c) 1999 Academic Press.
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Xu, C. Aligned Biodegradable Nanofibrous Structure: A Potential Scaffold for Blood Vessel Engineering. Biomaterials 2004, 25, 877– 886, DOI: 10.1016/s0142-9612(03)00593-3
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Aligned biodegradable nanofibrous structure: a potential scaffold for blood vessel engineering
Xu C Y; Inai R; Kotaki M; Ramakrishna S
Biomaterials (2004), 25 (5), 877-86 ISSN:0142-9612.
A unique biodegradable nanofibrous structure, aligned poly(L-lactid-co-epsilon-caprolactone) [P(LLA-CL)] (75:25) copolymer nanofibrous scaffold was produced by electrospinning. The diameter of the generated fibers was around 500 nm with an aligned topography which mimics the circumferential orientation of cells and fibrils found in the medial layer of a native artery. A favorable interaction between this scaffold with human coronary artery smooth muscle cells (SMCs) was demonstrated via MTS assay, phase contrast light microscopy, scanning electron microscopy, immunohistology assay and laser scanning confocal microscopy separately. Tissue culture polystyrene and plane solvent-cast P(LLA-CL) film were used as controls. The results showed that, the SMCs attached and migrated along the axis of the aligned nanofibers and expressed a spindle-like contractile phenotype; the distribution and organization of smooth muscle cytoskeleton proteins inside SMCs were parallel to the direction of the nanofibers; the adhesion and proliferation rate of SMCs on the aligned nanofibrous scaffold was significantly improved than on the plane polymer films. The above results strongly suggest that this synthetic aligned matrix combines with the advantages of synthetic biodegradable polymers, nanometer-scale dimension mimicking the natural ECM and a defined architecture replicating the in vivo-like vascular structure, may represent an ideal tissue engineering scaffold, especially for blood vessel engineering.
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Ju, Y. M.; Choi, J. S.; Atala, A.; Yoo, J. J.; Lee, S. J. Bilayered Scaffold for Engineering Cellularized Blood Vessels. Biomaterials 2010, 31, 4313– 4321, DOI: 10.1016/j.biomaterials.2010.02.002
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Bilayered scaffold for engineering cellularized blood vessels
Ju, Young Min; Choi, Jin San; Atala, Anthony; Yoo, James J.; Lee, Sang Jin
Biomaterials (2010), 31 (15), 4313-4321CODEN: BIMADU; ISSN:0142-9612. (Elsevier Ltd.)
Vascular scaffolds fabricated by electrospinning poly(ε-caprolactone) (PCL) and collagen were designed to provide adequate structural support as well as a favorable adhesion substrate for vascular cells. However, the presence of small-sized pores limits the efficacy of smooth muscle cells (SMC) seeding, as these cells could not adequately infiltrate into the scaffolds. To overcome this challenge, the authors developed a bilayered scaffolding system that provides different pore sizes to facilitate adequate cellular interactions. Based on the fact that pore size increases with the increase in fiber diam., 4 different fiber diams. (ranging 0.27-4.45 μm) were fabricated by electrospinning with controlled parameters. The fabricated scaffolds were examd. by evaluating cellular interactions, and the mech. properties were measured. Endothelial cells (EC) seeded on nanoscaled fibers showed enhanced cellular orientation and focal adhesion. Conversely, fabrication of a larger fiber diam. improved SMC infiltration into the scaffolds. To incorporate both of these properties into a scaffold, bilayered vascular scaffolds were produced. The inner layer yielded small diam. fibers and the outer layer provided large diam. fibers. The authors show that the bilayered scaffolds permit EC adhesion on the lumen and SMC infiltration into the outer layer. This study suggests that the use of bilayered scaffolds may lead to improved vessel formation.
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Ghasemi-Mobarakeh, L.; Prabhakaran, M. P.; Morshed, M.; Nasr-Esfahani, M.-H.; Ramakrishna, S. Electrospun Poly(ε-Caprolactone)/gelatin Nanofibrous Scaffolds for Nerve Tissue Engineering. Biomaterials 2008, 29, 4532– 4539, DOI: 10.1016/j.biomaterials.2008.08.007
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Electrospun poly(ε-caprolactone)/gelatin nanofibrous scaffolds for nerve tissue engineering
Ghasemi-Mobarakeh, Laleh; Prabhakaran, Molamma P.; Morshed, Mohammad; Nasr-Esfahani, Mohammad-Hossein; Ramakrishna, Seeram
Biomaterials (2008), 29 (34), 4532-4539CODEN: BIMADU; ISSN:0142-9612. (Elsevier Ltd.)
Nerve tissue engineering is one of the most promising methods to restore nerve systems in human health care. Scaffold design has pivotal role in nerve tissue engineering. Polymer blending is one of the most effective methods for providing new, desirable biocomposites for tissue-engineering applications. Random and aligned PCL/gelatin biocomposite scaffolds were fabricated by varying the ratios of PCL and gelatin concns. Chem. and mech. properties of PCL/gelatin nanofibrous scaffolds were measured by FTIR, porometry, contact angle and tensile measurements, while the in vitro biodegradability of the different nanofibrous scaffolds were evaluated too. PCL/gelatin 70:30 nanofiber was found to exhibit the most balanced properties to meet all the required specifications for nerve tissue and was used for in vitro culture of nerve stem cells (C17.2 cells). MTS assay and SEM results showed that the biocomposite of PCL/gelatin 70:30 nanofibrous scaffolds enhanced the nerve differentiation and proliferation compared to PCL nanofibrous scaffolds and acted as a pos. cue to support neurite outgrowth. It was found that the direction of nerve cell elongation and neurite outgrowth on aligned nanofibrous scaffolds is parallel to the direction of fibers. PCL/gelatin 70:30 nanofibrous scaffolds proved to be a promising biomaterial suitable for nerve regeneration.
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Yang, F.; Murugan, R.; Ramakrishna, S.; Wang, X.; Ma, Y.-X.; Wang, S. Fabrication of Nano-Structured Porous PLLA Scaffold Intended for Nerve Tissue Engineering. Biomaterials 2004, 25, 1891– 1900, DOI: 10.1016/j.biomaterials.2003.08.062
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Fabrication of nano-structured porous PLLA scaffold intended for nerve tissue engineering
Yang, F.; Murugan, R.; Ramakrishna, S.; Wang, X.; Ma, Y.-X.; Wang, S.
Biomaterials (2004), 25 (10), 1891-1900CODEN: BIMADU; ISSN:0142-9612. (Elsevier Science Ltd.)
Nerve tissue engineering (NTE) is one of the most promising methods to restore central nerve systems in human health care. Three-dimensional distribution and growth of cells within the porous scaffold are of clin. significance for NTE. In this study, an attempt was made to develop porous polymeric nano-fibrous scaffold using a biodegradable poly(L-lactic acid) (PLLA) for in vitro culture of nerve stem cells (NSCs). The processing of PLLA scaffold has been carried out by liq.-liq. phase sepn. method. The physico-chem. properties of the scaffold were fully characterized by using differential scanning calorimetry and SEM. These results confirmed that the prepd. scaffold is highly porous and fibrous with diams. down to nanometer scale. As our nano-structured PLLA scaffold mimics natural extracellular matrix, we have intended this biodegradable scaffold as cell carrier in NTE. The in vitro performance of NSCs seeded on nano-fibrous scaffold is addressed in this study. The cell cultural tests showed that the NSCs could differentiate on the nano-structured scaffold and the scaffold acted as a pos. cue to support neurite outgrowth. These results suggested that the nano-structured porous PLLA scaffold is a potential cell carrier in NTE.
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Zhong, Y.; Bellamkonda, R. V. Biomaterials for the Central Nervous System. J. R. Soc., Interface 2008, 5, 957– 975, DOI: 10.1098/rsif.2008.0071
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Biomaterials for the central nervous system
Zhong, Yinghui; Bellamkonda, Ravi V.
Journal of the Royal Society, Interface (2008), 5 (26), 957-975CODEN: JRSICU; ISSN:1742-5689. (Royal Society)
A review. Biomaterials are widely used to help treat neurol. disorders and/or improve functional recovery in the central nervous system (CNS). This article reviews the application of biomaterials in (i) shunting systems for hydrocephalus, (ii) cortical neural prosthetics, (iii) drug delivery in the CNS, (iv) hydrogel scaffolds for CNS repair, and (v) neural stem cell encapsulation for neurotrauma. The biol. and material requirements for the biomaterials in these applications are discussed. The difficulties that the biomaterials might face in each application and the possible solns. are also reviewed in this article.
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Oliveira, Á.; Corrêa-Velloso, J. d. C.; Glaser, T.; Ulrich, H. Stem Cells: Principles and Applications. Working with Stem Cells; Springer, 2016; pp 1– 14.
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Smith, A. G.; Heath, J. K.; Donaldson, D. D.; Wong, G. G.; Moreau, J.; Stahl, M.; Rogers, D. Inhibition of Pluripotential Embryonic Stem Cell Differentiation by Purified Polypeptides. Nature 1988, 336, 688– 690, DOI: 10.1038/336688a0
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Evans, M. J.; Kaufman, M. H. Establishment in Culture of Pluripotential Cells from Mouse Embryos. Nature 1981, 292, 154– 156, DOI: 10.1038/292154a0
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Establishment in culture of pluripotential cells from mouse embryos
Evans M J; Kaufman M H
Nature (1981), 292 (5819), 154-6 ISSN:0028-0836.
There is no expanded citation for this reference.
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Kurosawa, H. Methods for Inducing Embryoid Body Formation: In Vitro Differentiation System of Embryonic Stem Cells. J. Biosci. Bioeng. 2007, 103, 389– 398, DOI: 10.1263/jbb.103.389
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Methods for inducing embryoid body formation: in vitro differentiation system of embryonic stem cells
Kurosawa, Hiroshi
Journal of Bioscience and Bioengineering (2007), 103 (5), 389-398CODEN: JBBIF6; ISSN:1389-1723. (Society for Biotechnology, Japan)
When cultured in suspension without antidifferentiation factors, embryonic stem (ES) cells spontaneously differentiate and form three-dimensional multicellular aggregates called embryoid bodies (EBs). EBs recapitulate many aspects of cell differentiation during early embryogenesis, and play an important role in the differentiation of ES cells into a variety of cell types in vitro. There are several methods for inducing the formation of EBs from ES cells. The three basic methods are liq. suspension culture in bacterial-grade dishes, culture in methylcellulose semisolid media, and culture in hanging drops. Recently, the methods using a round-bottomed 96-well plate and a conical tube are adopted for forming EBs from predetd. nos. of ES cells. For the prodn. of large nos. of EBs, stirred-suspension culture using spinner flasks and bioreactors is performed. Each of these methods has its own peculiarity; thus, the features of formed EBs depending on the method used. Therefore, we should choose an appropriate method for EB formation according to the objective to be attained. In this review, we summarize the studies on in vitro differentiation of ES cells via EB formation and highlight the EB formation methods recently developed including the techniques, devices, and procedures involved.
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Tabar, V.; Studer, L. Pluripotent Stem Cells in Regenerative Medicine: Challenges and Recent Progress. Nat. Rev. Genet. 2014, 15, 82– 92, DOI: 10.1038/nrg3563
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Pluripotent stem cells in regenerative medicine: challenges and recent progress
Tabar, Viviane; Studer, Lorenz
Nature Reviews Genetics (2014), 15 (2), 82-92CODEN: NRGAAM; ISSN:1471-0056. (Nature Publishing Group)
A review. After years of incremental progress, several recent studies have succeeded in deriving disease-relevant cell types from human pluripotent stem cell (hPSC) sources. The prospect of an unlimited cell source, combined with promising preclin. data, indicates that hPSC technol. may be on the verge of clin. translation. In this Review, we discuss recent progress in directed differentiation, some of the new technologies that have facilitated the success of hPSC therapies and the remaining hurdles on the road towards developing hPSC-based cell therapies.
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Trounson, A.; Dewitt, N. D. Pluripotent Stem Cells Progressing to the Clinic. Nat. Rev. Mol. Cell Biol. 2016, 17, 194– 200, DOI: 10.1038/nrm.2016.10
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Pluripotent stem cells progressing to the clinic
Trounson, Alan; DeWitt, Natalie D.
Nature Reviews Molecular Cell Biology (2016), 17 (3), 194-200CODEN: NRMCBP; ISSN:1471-0072. (Nature Publishing Group)
Basic exptl. stem cell research has opened up the possibility of many diverse clin. applications; however, translation to clin. trials has been restricted to only a few diseases. To broaden this clin. scope, pluripotent stem cell derivs. provide a uniquely scalable source of functional differentiated cells that can potentially repair damaged or diseased tissues to treat a wide spectrum of diseases and injuries. However, gathering sound data on their distribution, longevity, function and mechanisms of action in host tissues is imperative to realizing their clin. benefit. The large-scale availability of treatments involving pluripotent stem cells remains some years away, because of the long and demanding regulatory pathway that is needed to ensure their safety.
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Mahla, R. S. Stem Cells Applications in Regenerative Medicine and Disease Therapeutics. Int. J. Cell Biol. 2016, 2016, 6940283, DOI: 10.1155/2016/6940283
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Stem Cells Applications in Regenerative Medicine and Disease Therapeutics
Mahla Ranjeet Singh
International journal of cell biology (2016), 2016 (), 6940283 ISSN:1687-8876.
Regenerative medicine, the most recent and emerging branch of medical science, deals with functional restoration of tissues or organs for the patient suffering from severe injuries or chronic disease. The spectacular progress in the field of stem cell research has laid the foundation for cell based therapies of disease which cannot be cured by conventional medicines. The indefinite self-renewal and potential to differentiate into other types of cells represent stem cells as frontiers of regenerative medicine. The transdifferentiating potential of stem cells varies with source and according to that regenerative applications also change. Advancements in gene editing and tissue engineering technology have endorsed the ex vivo remodelling of stem cells grown into 3D organoids and tissue structures for personalized applications. This review outlines the most recent advancement in transplantation and tissue engineering technologies of ESCs, TSPSCs, MSCs, UCSCs, BMSCs, and iPSCs in regenerative medicine. Additionally, this review also discusses stem cells regenerative application in wildlife conservation.
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Segers, V. F. M.; Lee, R. T. Stem-Cell Therapy for Cardiac Disease. Nature 2008, 451, 937– 942, DOI: 10.1038/nature06800
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Stem-cell therapy for cardiac disease
Segers, Vincent F. M.; Lee, Richard T.
Nature (London, United Kingdom) (2008), 451 (7181), 937-942CODEN: NATUAS; ISSN:0028-0836. (Nature Publishing Group)
A review. Heart failure is the leading cause of death worldwide, and current therapies only delay progression of the disease. Lab. expts. and recent clin. trials suggest that cell-based therapies can improve cardiac function, and the implications of this for cardiac regeneration are causing great excitement. Bone-marrow-derived progenitor cells and other progenitor cells can differentiate into vascular cell types, restoring blood flow. More recently, resident cardiac stem cells have been shown to differentiate into multiple cell types present in the heart, including cardiac muscle cells, indicating that the heart is not terminally differentiated. These new findings have stimulated optimism that the progression of heart failure can be prevented or even reversed with cell-based therapy.
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Lindvall, O.; Kokaia, Z. Stem Cells for the Treatment of Neurological Disorders. Nature 2006, 441, 1094, DOI: 10.1038/nature04960
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Stem cells for the treatment of neurological disorders
Lindvall, Olle; Kokaia, Zaal
Nature (London, United Kingdom) (2006), 441 (7097), 1094-1096CODEN: NATUAS; ISSN:0028-0836. (Nature Publishing Group)
A review. Many common neurol. disorders, such as Parkinson's disease, stroke and multiple sclerosis, are caused by a loss of neurons and glial cells. In recent years, neurons and glia have been generated successfully from stem cells in culture, fueling efforts to develop stem-cell-based transplantation therapies for human patients. More recently, efforts have been extended to stimulating the formation and preventing the death of neurons and glial cells produced by endogenous stem cells within the adult central nervous system. The next step is to translate these exciting advances from the lab. into clin. useful therapies.
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Murphy, W. L.; McDevitt, T. C.; Engler, A. J. Materials as Stem Cell Regulators. Nat. Mater. 2014, 13, 547– 557, DOI: 10.1038/nmat3937
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Materials as stem cell regulators
Murphy, William L.; McDevitt, Todd C.; Engler, Adam J.
Nature Materials (2014), 13 (6), 547-557CODEN: NMAACR; ISSN:1476-1122. (Nature Publishing Group)
A review. The stem cell/material interface is a complex, dynamic microenvironment in which the cell and the material cooperatively dictate one another's fate: the cell by remodelling its surroundings, and the material through its inherent properties (such as adhesivity, stiffness, nanostructure or degradability). Stem cells in contact with materials are able to sense their properties, integrate cues via signal propagation and ultimately translate parallel signalling information into cell fate decisions. However, discovering the mechanisms by which stem cells respond to inherent material characteristics is challenging because of the highly complex, multicomponent signalling milieu present in the stem cell environment. In this Review, we discuss recent evidence that shows that inherent material properties may be engineered to dictate stem cell fate decisions, and overview a subset of the operative signal transduction mechanisms that have begun to emerge. Further developments in stem cell engineering and mechanotransduction are poised to have substantial implications for stem cell biol. and regenerative medicine.
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Semeano, A. T.; Glaser, T.; Ulrich, H. Scaffolds for Embryonic Stem Cell Growth and Differentiation. Working with Stem Cells; Springer, 2016; pp 347– 365.
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Krishna, L.; Dhamodaran, K.; Jayadev, C.; Chatterjee, K.; Shetty, R.; Khora, S. S. Nanostructured Scaffold as a Determinant of Stem Cell Fate. Stem Cell Res. Ther. 2016, 7, 188, DOI: 10.1186/s13287-016-0440-y
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Nanostructured scaffold as a determinant of stem cell fate
Krishna, Lekshmi; Dhamodaran, Kamesh; Jayadev, Chaitra; Chatterjee, Kaushik; Shetty, Rohit; Khora, S. S.; Das, Debashish
Stem Cell Research & Therapy (2016), 7 (), 188/1-188/12CODEN: SCRTEK; ISSN:1757-6512. (BioMed Central Ltd.)
A review. The functionality of stem cells is tightly regulated by cues from the niche, comprising both intrinsic and extrinsic cell signals. Besides chem. and growth factors, biophys. signals are important components of extrinsic signals that dictate the stem cell properties. The materials used in the fabrication of scaffolds provide the chem. cues whereas the shape of the scaffolds provides the biophys. cues. The effect of the chem. compn. of the scaffolds on stem cell fate is well researched. Biophys. signals such as nanotopog., mech. forces, stiffness of the matrix, and roughness of the biomaterial influence the fate of stem cells. However, not much is known about their role in signaling crosstalk, stem cell maintenance, and directed differentiation. Among the various techniques for scaffold design, nanotechnol. has special significance. The role of nanoscale topog. in scaffold design for the regulation of stem cell behavior has gained importance in regenerative medicine. Nanotechnol. allows manipulation of highly advanced surfaces/scaffolds for optimal regulation of cellular behavior. Techniques such as electrospinning, soft lithog., microfluidics, carbon nanotubes, and nanostructured hydrogel are described in this review, along with their potential usage in regenerative medicine. We have also provided a brief insight into the potential signaling crosstalk that is triggered by nanomaterials that dictate a specific outcome of stem cells. This concise review compiles recent developments in nanoscale architecture and its importance in directing stem cell differentiation for prospective therapeutic applications.
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Vert, M.; Li, S. M.; Spenlehauer, G.; Guerin, P. Bioresorbability and Biocompatibility of Aliphatic Polyesters. J. Mater. Sci.: Mater. Med. 1992, 3, 432– 446, DOI: 10.1007/bf00701240
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Bioresorbability and biocompatibility of aliphatic polyesters
Vert, M.; Li, S. M.; Spenlehauer, G.; Guerin, P.
Journal of Materials Science: Materials in Medicine (1992), 3 (6), 432-46CODEN: JSMMEL; ISSN:0957-4530.
A review with 103 refs. on the complex phenomena of biodegradability and biocompatibility of polyesters, esp. poly(α-hydroxy acids), for temporary surgical and pharmacol. applications. The degrdn. of a polymer leads to the delivery of low mol. wt. degrdn. byproducts whose effects on the host body have to be considered. The consequences of the absence of std. terminol. are first discussed with respect to words such as biodegradable and bioresorbable. Poly(α-hydroxy acids) derived from lactic and glycolic acids are discussed, as well as biocompatibility, biodegradability, bioresorbability, mechanism of hydrolysis (enzymic vs. simple chem.), polymodality of mol. wt. distributions during degrdn. and the effects of the presence of oligomers. Finally, some specific comments are made on other aliph. polyesters such as poly(hydroxy butyrate) and poly(β-malic acid).
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Hutmacher, D. W. Scaffolds in Tissue Engineering Bone and Cartilage. Biomaterials 2000, 21, 2529– 2543, DOI: 10.1016/s0142-9612(00)00121-6
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Scaffolds in tissue engineering bone and cartilage
Hutmacher, D. W.
Biomaterials (2000), 21 (24), 2529-2543CODEN: BIMADU; ISSN:0142-9612. (Elsevier Science Ltd.)
A review with 82 refs. Musculoskeletal tissue, bone and cartilage are under extensive investigation in tissue engineering research. A no. of biodegradable and bioresorbable materials, as well as scaffold designs, have been exptl. and/or clin. studied. Ideally, a scaffold should have the following characteristics: (i) 3-dimensional and highly porous with an interconnected pore network for cell growth and flow transport of nutrients and metabolic waste; (ii) biocompatible and bioresorbable with a controllable degrdn. and resorption rate to match cell/tissue growth in vitro and/or in vivo; (iii) suitable surface chem. for cell attachment, proliferation, and differentiation and (iv) mech. properties to match those of the tissues at the site of implantation. This paper reviews research on the tissue engineering of bone and cartilage from the polymeric scaffold point of view.
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Nair, L. S.; Laurencin, C. T. Biodegradable Polymers as Biomaterials. Prog. Polym. Sci. 2007, 32, 762– 798, DOI: 10.1016/j.progpolymsci.2007.05.017
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Biodegradable polymers as biomaterials
Nair, Lakshmi S.; Laurencin, Cato T.
Progress in Polymer Science (2007), 32 (8-9), 762-798CODEN: PRPSB8; ISSN:0079-6700. (Elsevier Ltd.)
A review. During the past 2 decades significant advances were made in the development of biodegradable polymeric materials for biomedical applications. Degradable polymeric biomaterials are preferred candidates for developing therapeutic devices such as temporary prostheses, 3-dimensional porous structures as scaffolds for tissue engineering and as controlled/sustained release drug delivery vehicles. Each of these applications demands materials with specific phys., chem., biol., biomech. and degrdn. properties to provide efficient therapy. Consequently, a wide range of natural or synthetic polymers capable of undergoing degrdn. by hydrolytic or enzymic route are being investigated for biomedical applications. This review summarizes the main advances published over the last 15 years, outlining the synthesis, biodegradability and biomedical applications of biodegradable synthetic and natural polymers.
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Mooney, D. Stabilized Polyglycolic Acid Fibre-Based Tubes for Tissue Engineering. Biomaterials 1996, 17, 115– 124, DOI: 10.1016/0142-9612(96)85756-5
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Stabilized polyglycolic acid fiber-based tubes for tissue engineering
Mooney, D. J.; Mazzoni, C. L.; Breuer, C.; McNamara, K.; Hern, D.; Vacanti, J. P.; Langer, R.
Biomaterials (1996), 17 (2), 115-24CODEN: BIMADU; ISSN:0142-9612. (Elsevier)
Polyglycolic acid (PGA) fiber meshes are attractive candidates to transplant cells, but they are incapable of resisting significant compressional forces. To stabilize PGA meshes, atomized solns. of poly(L-lactic acid) (PLLA) and a 50/50 copolymer of poly(D,L-lactic-co-glycolic acid) (PLGA) dissolved in chloroform were sprayed over meshes formed into hollow tubes. The PLLA and PLGA coated the PGA fibers and phys. bonded adjacent fibers. The pattern and extent of bonding was controlled by the concn. of polymer in the atomized soln. and the total mass of polymer sprayed on the device. The compression resistance of devices increased with the extent of bonding, and PLLA bonded tubes resisted larger compressive forces than PLGA bonded tubes. Tubes bonded with PLLA degraded more slowly than devices bonded with PLGA. Implantation of PLLA bonded tubes into rats revealed that the devices maintained their structure during fibrovascular tissue ingrowth, resulting in the formation of a tubular structure with a central lumen. The potential of these devices to engineer specific tissues was exhibited by the finding that smooth muscle cells and endothelial cells seeded onto devices in vitro formed a tubular tissue with appropriate cell distribution.
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Moutos, F. T.; Freed, L. E.; Guilak, F. A Biomimetic Three-Dimensional Woven Composite Scaffold for Functional Tissue Engineering of Cartilage. Nat. Mater. 2007, 6, 162– 167, DOI: 10.1038/nmat1822
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A biomimetic three-dimensional woven composite scaffold for functional tissue engineering of cartilage
Moutos, Franklin T.; Freed, Lisa E.; Guilak, Farshid
Nature Materials (2007), 6 (2), 162-167CODEN: NMAACR; ISSN:1476-1122. (Nature Publishing Group)
Tissue engineering seeks to repair or regenerate tissues through combinations of implanted cells, biomaterial scaffolds and biol. active mols. The rapid restoration of tissue biomech. function remains an important challenge, emphasizing the need to replicate structural and mech. properties using novel scaffold designs. Here we present a microscale 3D weaving technique to generate anisotropic 3D woven structures as the basis for novel composite scaffolds that are consolidated with a chondrocyte-hydrogel mixt. into cartilage tissue constructs. Composite scaffolds show mech. properties of the same order of magnitude as values for native articular cartilage, as measured by compressive, tensile and shear testing. Moreover, our findings showed that porous composite scaffolds could be engineered with initial properties that reproduce the anisotropy, viscoelasticity and tension-compression nonlinearity of native articular cartilage. Such scaffolds uniquely combine the potential for load-bearing immediately after implantation in vivo with biol. support for cell-based tissue regeneration without requiring cultivation in vitro.
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Verrier, S.; Blaker, J. J.; Maquet, V.; Hench, L. L.; Boccaccini, A. R. PDLLA/Bioglass Composites for Soft-Tissue and Hard-Tissue Engineering: An in Vitro Cell Biology Assessment. Biomaterials 2004, 25, 3013– 3021, DOI: 10.1016/j.biomaterials.2003.09.081
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PDLLA/Bioglass composites for soft-tissue and hard-tissue engineering: an in vitro cell biology assessment
Verrier, Sophie; Blaker, Jonny J.; Maquet, Veronique; Hench, Larry L.; Boccaccini, Aldo R.
Biomaterials (2004), 25 (15), 3013-3021CODEN: BIMADU; ISSN:0142-9612. (Elsevier Science Ltd.)
The aim of this study was to examine the effect of increased content of 45S5 Bioglass (0-40%) in poly(dl-lactic acid) (PDLLA) porous foams on the behavior of MG-63 (human osteosarcoma cell line) and A549 cells (human lung carcinoma cell line). The ability of these cell lines to grow on bioactive composites was quant. investigated in order to assess the potentiality for their use in hard and soft-tissue engineering. Two hours after cell seeding, an increase of cell adhesion according to the increased content of Bioglass present in the foams for both cell types was obsd. Cell proliferation studies performed over a period of 4 wk showed a better aptitude of the A549 cells to proliferate on PDLLA foams contg. 5% Bioglass when compared to the proliferation on foams with 40% Bioglass. A lower proliferation rate was obtained for cells on pure PDLLA. SEM anal. showed for both cell types the presence of cells inside the porous structure of the foams. These results confirmed the biocompatibility of PDLLA/Bioglass composite foams and the pos. effect of Bioglass on MG-63 cell behavior and also showed for the first time the possibility for human lung epithelial type II cells to adhere and proliferate on these porous scaffolds. In addn., we describe a pos. effect of 45S5 Bioglass on A549 cell behavior in a dose-dependent manner, indicating the potential of using PDLLA/Bioglass composites with an optimal concn. of 45S5 Bioglass not only in bone tissue engineering but also in lung tissue engineering.
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Yang, F.; Xu, C. Y.; Kotaki, M.; Wang, S.; Ramakrishna, S. Characterization of Neural Stem Cells on Electrospun poly(L-Lactic Acid) Nanofibrous Scaffold. J. Biomater. Sci., Polym. Ed. 2004, 15, 1483– 1497, DOI: 10.1163/1568562042459733
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Characterization of neural stem cells on electrospun poly(L-lactic acid) nanofibrous scaffold
Yang, F.; Xu, C. Y.; Kotaki, M.; Wang, S.; Ramakrishna, S.
Journal of Biomaterials Science, Polymer Edition (2004), 15 (12), 1483-1497CODEN: JBSEEA; ISSN:0920-5063. (VSP)
Nanofibrous poly(L-lactic acid) (PLLA) scaffolds were fabricated by an electrospinning technique and characterized by SEM, mercury porosimeter, at. force microscopy and contact-angle test. The produced PLLA fibers with diams. ranging from 150 to 350 nm were randomly oriented with interconnected pores varying from several μm to about 140 μm in-between to form a three-dimensional architecture, which resembles the natural extracellular matrix structure in human body. The in vitro cell culture study was performed and the results indicate that the nanofibrous scaffold not only supports neural stem cell (NSC) differentiation and neurites out-growth, but also promotes NSC adhesion. The favorable interaction between the NSCs and the nanofibrous scaffold may be due to the greatly improved surface roughness of the electrospun nanofibrous scaffold. As evidenced by this study, the electrospun nanofibrous scaffold is expected to play a significant role in neural tissue engineering.
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Yang, F.; Murugan, R.; Wang, S.; Ramakrishna, S. Electrospinning of Nano/micro Scale Poly(l-Lactic Acid) Aligned Fibers and Their Potential in Neural Tissue Engineering. Biomaterials 2005, 26, 2603– 2610, DOI: 10.1016/j.biomaterials.2004.06.051
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Electrospinning of nano/micro scale poly(L-lactic acid) aligned fibers and their potential in neural tissue engineering
Yang, F.; Murugan, R.; Wang, S.; Ramakrishna, S.
Biomaterials (2005), 26 (15), 2603-2610CODEN: BIMADU; ISSN:0142-9612. (Elsevier Ltd.)
Efficacy of aligned poly(-lactic acid) (PLLA) nano/micro fibrous scaffolds for neural tissue engineering is described and their performance with random PLLA scaffolds is compared as well in this study. Perfectly aligned PLLA fibrous scaffolds were fabricated by an electrospinning technique under optimum condition and the diam. of the electrospun fibers can easily be tailored by adjusting the concn. of polymer soln. As the structure of PLLA scaffold was intended for neural tissue engineering, its suitability was evaluated in vitro using neural stem cells (NSCs) as a model cell line. Cell morphol., differentiation and neurite outgrowth were studied by various microscopic techniques. The results show that the direction of NSC elongation and its neurite outgrowth is parallel to the direction of PLLA fibers for aligned scaffolds. No significant changes were obsd. on the cell orientation with respect to the fiber diams. However, the rate of NSC differentiation was higher for PLLA nanofibers than that of micro fibers and it was independent of the fiber alignment. Based on the exptl. results, the aligned nanofibrous PLLA scaffold could be used as a potential cell carrier in neural tissue engineering.
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Kweon, H. A Novel Degradable Polycaprolactone Networks for Tissue Engineering. Biomaterials 2003, 24, 801– 808, DOI: 10.1016/s0142-9612(02)00370-8
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A novel degradable polycaprolactone networks for tissue engineering
Kweon, HaeYong; Yoo, Mi Kyong; Park, In Kyu; Kim, Tae Hee; Lee, Hyun Chul; Lee, Hyun-Sook; Oh, Jong-Suk; Akaike, Toshihiro; Cho, Chong-Su
Biomaterials (2003), 24 (5), 801-808CODEN: BIMADU; ISSN:0142-9612. (Elsevier Science Ltd.)
Polycaprolactone (PCL) macromer was obtained by the reaction of PCL diol with acryloyl chloride and confirmed using Fourier transform IR and NMR spectrometer. Novel degradable PCL networks were prepd. through photopolymn. of the PCL macromer. Thermal, mech., and morphol. characteristics as well as degradability and biocompatibility of the PCL networks were investigated. DSC showed that the melting temp. and the calcd. wt. av. crystallinity of PCL networks were decreased with a decrease of mol. wt. of PCL diols due to the increased crosslinking d. Thermal stability of PCL networks was higher than that of PCL diols. PCL networks showed faster degrdn., and higher compressive modulus and compressive recovery ratios than those of PCL itself because of their low crystallinity and the modification of terminal groups. The porosity of the PCL networks can be controlled by the amts. and size of porogen used. MG-63 osteoblast cell was attached and proliferated on PCL networks. PCL networks therefore may have considerable potential as scaffold for tissue engineering.
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Yang, S.; Leong, K.-F.; Du, Z.; Chua, C.-K. The Design of Scaffolds for Use in Tissue Engineering. Part I. Traditional Factors. Tissue Eng. 2001, 7, 679– 689, DOI: 10.1089/107632701753337645
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The design of scaffolds for use in tissue engineering. Part I. Traditional factors
Yang S; Leong K F; Du Z; Chua C K
Tissue engineering (2001), 7 (6), 679-89 ISSN:1076-3279.
In tissue engineering, a highly porous artificial extracellular matrix or scaffold is required to accommodate mammalian cells and guide their growth and tissue regeneration in three dimensions. However, existing three-dimensional scaffolds for tissue engineering proved less than ideal for actual applications, not only because they lack mechanical strength, but they also do not guarantee interconnected channels. In this paper, the authors analyze the factors necessary to enhance the design and manufacture of scaffolds for use in tissue engineering in terms of materials, structure, and mechanical properties and review the traditional scaffold fabrication methods. Advantages and limitations of these traditional methods are also discussed.
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Chen, C.-C.; Chueh, J.-Y.; Tseng, H.; Huang, H.-M.; Lee, S.-Y. Preparation and Characterization of Biodegradable PLA Polymeric Blends. Biomaterials 2003, 24, 1167– 1173, DOI: 10.1016/s0142-9612(02)00466-0
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Preparation and characterization of biodegradable PLA polymeric blends
Chen, Chien-Chung; Chueh, Ju-Yu; Tseng, How; Huang, Haw-Ming; Lee, Sheng-Yang
Biomaterials (2003), 24 (7), 1167-1173CODEN: BIMADU; ISSN:0142-9612. (Elsevier Science Ltd.)
The purpose of this study was to fine-tune the mech. properties of high mol.-wt. poly-l-lactic acid (PLLA), esp. to increase its toughness without sacrificing too much of its original strength. Besides of its long degrdn. time, PLLA is usually hard and brittle, which hinders its usage in medical applications, i.e., orthopedic and dental surgery. Some modifications, such as the addn. of plasticizers or surfactants/compatibilizers, are usually required to improve its original properties. PDLLA can degrade quickly due to its amorphous structure, thus shortening the degrdn. time of PLLA/PDLLA blends. Blends of biodegradable poly-l-lactic acid (PLLA) and poly-dl-lactic acid (PDLLA) or polycaprolactone (PCL), in addn. to a third component, the surfactant-a copolymer of ethylene oxide and propylene oxide, were prepd. by blending these three polymers at various ratios using dichloromethane as a solvent. The wt. percentages of PLLA/PDLLA (or PCL) blends were 100%/0%, 80%/20%, 60%/40%, 50%/50%, 40%/60%, 20%/80% and 0%/100%, resp. Phys. properties such as the cryst. m.p., glass transition point (Tg), phase behavior, degrdn. behavior, and other mech. properties were characterized by thermogravimetric anal., DSC, IR spectroscopy, gel permeation chromatog., and dynamic mech. anal. (DMA). DSC data indicate that PLLA/PDLLA blends without the surfactant had two Tg's. With the addn. of the surfactant, there was a linear shift of the single Tg as a function of compn., with lower percentages of PLLA producing lower glass transition temps. indicating that better miscibility had been achieved. DMA data show that the 40/60 PLLA/PDLLA blends without the surfactant had high elastic modulus and elongation, and similar results were obsd. after adding 2% surfactant into the blends. The 50/50 PLLA/PDLLA/2% surfactant blend had the highest elastic modulus, yield strength, and break strength compared with other ratios of PLLA/PDLLA/2% surfactant blends. The elongation at break of 50/50 PLLA/PDLLA was similar to that of PLLA. Again, the elongation at break of 50/50 PLLA/PDLLA/2% surfactant was almost 1.2-1.9 times higher than that of 50/50 PLLA/PDLLA and PLLA. Elongation of PLLA increased with the addn. of PCL, but the strength decreased at the same time. In conclusions, adding PDLLA and surfactant to PLLA via soln.-blending may be an effective way to make PLLA tougher and more suitable to use in orthopedic or dental applications.
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Ulery, B. D.; Nair, L. S.; Laurencin, C. T. Biomedical Applications of Biodegradable Polymers. J. Polym. Sci., Part B: Polym. Phys. 2011, 49, 832– 864, DOI: 10.1002/polb.22259
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Biomedical applications of biodegradable polymers
Ulery, Bret D.; Nair, Lakshmi S.; Laurencin, Cato T.
Journal of Polymer Science, Part B: Polymer Physics (2011), 49 (12), 832-864CODEN: JPBPEM; ISSN:0887-6266. (John Wiley & Sons, Inc.)
A review. Utilization of polymers as biomaterials has greatly impacted the advancement of modern medicine. Specifically, polymeric biomaterials that are biodegradable provide the significant advantage of being able to be broken down and removed after they have served their function. Applications are wide ranging with degradable polymers being used clin. as surgical sutures and implants. To fit functional demand, materials with desired phys., chem., biol., biomech., and degrdn. properties must be selected. Fortunately, a wide range of natural and synthetic degradable polymers has been investigated for biomedical applications with novel materials constantly being developed to meet new challenges. This review summarizes the most recent advances in the field over the past 4 years, specifically highlighting new and interesting discoveries in tissue engineering and drug delivery applications. © 2011 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2011.
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Chen, J.; Dong, R.; Ge, J.; Guo, B.; Ma, P. X. Biocompatible, Biodegradable, and Electroactive Polyurethane-Urea Elastomers with Tunable Hydrophilicity for Skeletal Muscle Tissue Engineering. ACS Appl. Mater. Interfaces 2015, 7, 28273– 28285, DOI: 10.1021/acsami.5b10829
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Biocompatible, Biodegradable, and Electroactive Polyurethane-Urea Elastomers with Tunable Hydrophilicity for Skeletal Muscle Tissue Engineering
Chen, Jing; Dong, Ruonan; Ge, Juan; Guo, Baolin; Ma, Peter X.
ACS Applied Materials & Interfaces (2015), 7 (51), 28273-28285CODEN: AAMICK; ISSN:1944-8244. (American Chemical Society)
It remains a challenge to develop electroactive and elastic biomaterials to mimic the elasticity of soft tissue and to regulate the cell behavior during tissue regeneration. We designed and synthesized a series of novel electroactive and biodegradable polyurethane-urea (PUU) copolymers with elastomeric property by combining the properties of polyurethanes and conducting polymers. The electroactive PUU copolymers were synthesized from amine capped aniline trimer (ACAT), dimethylol propionic acid (DMPA), polylactide, and hexamethylene diisocyanate. The electroactivity of the PUU copolymers were studied by UV-vis spectroscopy and cyclic voltammetry. Elasticity and Young's modulus were tailored by the polylactide segment length and ACAT content. Hydrophilicity of the copolymer films was tuned by changing DMPA content and doping of the copolymer. Cytotoxicity of the PUU copolymers was evaluated by mouse C2C12 myoblast cells. The myogenic differentiation of C2C12 myoblasts on copolymer films was also studied by analyzing the morphol. of myotubes and relative gene expression during myogenic differentiation. The chem. structure, thermal properties, surface morphol., and processability of the PUU copolymers were characterized by NMR, FT-IR, gel permeation chromatog. (GPC), thermogravimetric anal. (TGA), differential scanning calorimetry (DSC), x-ray diffraction (x-ray diffraction), SEM, at. force microscopy (AFM), and soly. testing, resp. Those biodegradable electroactive elastic PUU copolymers are promising materials for repair of soft tissues such as skeletal muscle, cardiac muscle, and nerve.
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Cui, H.; Liu, Y.; Deng, M.; Pang, X.; Zhang, P.; Wang, X.; Chen, X.; Wei, Y. Synthesis of Biodegradable and Electroactive Tetraaniline Grafted Poly(ester Amide) Copolymers for Bone Tissue Engineering. Biomacromolecules 2012, 13, 2881– 2889, DOI: 10.1021/bm300897j
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Synthesis of Biodegradable and Electroactive Tetraaniline Grafted Poly(ester amide) Copolymers for Bone Tissue Engineering
Cui, Haitao; Liu, Yadong; Deng, Mingxiao; Pang, Xuan; Zhang, Peibiao; Wang, Xianhong; Chen, Xuesi; Wei, Yen
Biomacromolecules (2012), 13 (9), 2881-2889CODEN: BOMAF6; ISSN:1525-7797. (American Chemical Society)
Biodegradable poly(ester amide)s have recently been used as biomaterials due to their desirable chem. and biol. characteristics as well as their mech. properties, which are amendable for material processing. In this study, electroactive tetraaniline (TA) grafted poly(ester amide)s were successfully synthesized and characterized. The poly(ester amide)s-graft-tetraaniline copolymers (PEA-g-TA) exhibited good electroactivity, mech. properties, and biodegradability. The biocompatibility of the PEA-g-TA copolymers in vitro was systematically studied, which demonstrated that they were nontoxic and led to favorable adhesion and proliferation of mouse preosteoblastic MC3T3-E1 cells. Moreover, the PEA-g-TA copolymers stimulated by pulsed elec. signal could serve to promote the differentiation of MC3T3-E1 cells compared with TCPs. Hence, the biodegradable and electroactive PEA-g-TA copolymers possessed the properties in favor of the long-time potential application in vivo (elec. stimulation directly to the desired area) as bone repair scaffold materials in tissue engineering.
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Balint, R.; Cassidy, N. J.; Cartmell, S. H. Conductive Polymers: Towards a Smart Biomaterial for Tissue Engineering. Acta Biomater. 2014, 10, 2341– 2353, DOI: 10.1016/j.actbio.2014.02.015
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Conductive polymers: Towards a smart biomaterial for tissue engineering
Balint, Richard; Cassidy, Nigel J.; Cartmell, Sarah H.
Acta Biomaterialia (2014), 10 (6), 2341-2353CODEN: ABCICB; ISSN:1742-7061. (Elsevier Ltd.)
A review. Developing stimulus-responsive biomaterials with easy-to-tailor properties is a highly desired goal of the tissue engineering community. A novel type of electroactive biomaterial, the conductive polymer, promises to become one such material. Conductive polymers are already used in fuel cells, computer displays and microsurgical tools, and are now finding applications in the field of biomaterials. These versatile polymers can be synthesized alone, as hydrogels, combined into composites or electrospun into microfibres. They can be created to be biocompatible and biodegradable. Their phys. properties can easily be optimized for a specific application through binding biol. important mols. into the polymer using one of the many available methods for their functionalization. Their conductive nature allows cells or tissue cultured upon them to be stimulated, the polymers' own phys. properties to be influenced post-synthesis and the drugs bound in them released, through the application of an elec. signal. It is thus little wonder that these polymers are becoming very important materials for biosensors, neural implants, drug delivery devices and tissue engineering scaffolds. Focusing mainly on polypyrrole, polyaniline and poly(3,4-ethylenedioxythiophene), we review conductive polymers from the perspective of tissue engineering. The basic properties of conductive polymers, their chem. and electrochem. synthesis, the phenomena underlying their cond. and the ways to tailor their properties (functionalization, composites, etc.) are discussed.
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Ateh, D. D.; Navsaria, H. A.; Vadgama, P. Polypyrrole-Based Conducting Polymers and Interactions with Biological Tissues. J. R. Soc., Interface 2006, 3, 741– 752, DOI: 10.1098/rsif.2006.0141
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Polypyrrole-based conducting polymers and interactions with biological tissues
Ateh, D. D.; Navsaria, H. A.; Vadgama, P.
Journal of the Royal Society, Interface (2006), 3 (11), 741-752CODEN: JRSICU; ISSN:1742-5689. (Royal Society)
A review. Polypyrrole (PPy) is a conjugated polymer that displays particular electronic properties including cond. In biomedical applications, it is usually electrochem. generated with the incorporation of any anionic species including also neg. charged biol. macromols. such as proteins and polysaccharides to give composite materials. In biomedical research, it has mainly been assessed for its role as a reporting interface in biosensors. However, there is an increasing literature on the application of PPy as a potentially elec. addressable tissue/cell support substrate. Here, we review studies that have considered such PPy based conducting polymers in direct contact with biol. tissues and conclude that due to its versatile functional properties, it could contribute to a new generation of biomaterials.
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Svennersten, K.; Bolin, M. H.; Jager, E. W. H.; Berggren, M.; Richter-Dahlfors, A. Electrochemical Modulation of Epithelia Formation Using Conducting Polymers. Biomaterials 2009, 30, 6257– 6264, DOI: 10.1016/j.biomaterials.2009.07.059
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Electrochemical modulation of epithelia formation using conducting polymers
Svennersten, Karl; Bolin, Maria H.; Jager, Edwin W. H.; Berggren, Magnus; Richter-Dahlfors, Agneta
Biomaterials (2009), 30 (31), 6257-6264CODEN: BIMADU; ISSN:0142-9612. (Elsevier Ltd.)
Conducting polymers are soft, flexible materials, exhibiting material properties that can be reversibly changed by electrochem. altering the redox state. Surface chem. is an important determinant for the mol. events of cell adhesion. Therefore, we analyzed whether the redox state of the conducting polymer PEDOT:Tosylate can be used to control epithelial cell adhesion and proliferation. A functionalized cell culture dish comprising two adjacent electrode surfaces was developed. Upon electronic addressing, reduced and oxidized surfaces are created within the same device. Simultaneous anal. of how a homogeneous epithelial MDCK cell population responded to the electrodes revealed distinct surface-specific differences. Presentation of functional fibronectin on the reduced electrode promoted focal adhesion formation, involving αvβ3 integrin, cell proliferation, and ensuing formation of polarized monolayers. In contrast, the oxidized surface harbored only few cells with deranged morphol. showing no indication of proliferation. This stems from the altered fibronectin conformation, induced by the different surface chem. of the PEDOT:Tosylate electrode in the oxidized state. Our results demonstrate a novel use of PEDOT:Tosylate as a cell-hosting material in multiple-electrode systems, where cell adhesion and proliferation can be controlled by electrochem. modulation of surface properties.
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Bolin, M. H.; Svennersten, K.; Wang, X.; Chronakis, I. S.; Richter-Dahlfors, A.; Jager, E. W. H.; Berggren, M. Nano-Fiber Scaffold Electrodes Based on PEDOT for Cell Stimulation. Sens. Actuators, B 2009, 142, 451– 456, DOI: 10.1016/j.snb.2009.04.062
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Nano-fiber scaffold electrodes based on PEDOT for cell stimulation
Bolin, Maria H.; Svennersten, Karl; Wang, Xiangjun; Chronakis, Ioannis S.; Richter-Dahlfors, Agneta; Jager, Edwin W. H.; Berggren, Magnus
Sensors and Actuators, B: Chemical (2009), 142 (2), 451-456CODEN: SABCEB; ISSN:0925-4005. (Elsevier B.V.)
Electronically conductive and electrochem. active 3D-scaffolds based on electrospun poly(ethylene terephthalate) (PET) nano-fibers are reported. Vapor phase polymn. was employed to achieve an uniform and conformal coating of poly(3,4-ethylenedioxythiophene) doped with tosylate (PEDOT:tosylate) on the nano-fibers. The PEDOT coatings had a large impact on the wettability, turning the hydrophobic PET fibers super-hydrophilic. SH-SY5Y neuroblastoma cells were grown on the PEDOT coated fibers. The SH-SY5Y cells adhered well and showed healthy morphol. These elec. active scaffolds were used to induce Ca2+ signalling in SH-SY5Y neuroblastoma cells. PEDOT:tosylate coated nano-fibers represent a class of 3D host environments that combines excellent adhesion and proliferation for neuronal cells with the possibility to regulate their signalling.
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Bendrea, A.-D.; Cianga, L.; Cianga, I. Review Paper: Progress in the Field of Conducting Polymers for Tissue Engineering Applications. J. Biomater. Appl. 2011, 26, 3– 84, DOI: 10.1177/0885328211402704
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Review paper: progress in the field of conducting polymers for tissue engineering applications
Bendrea, Anca-Dana; Cianga, Luminita; Cianga, Ioan
Journal of Biomaterials Applications (2011), 26 (1), 3-84CODEN: JBAPEL; ISSN:0885-3282. (Sage Publications Ltd.)
This review focuses on one of the most exciting applications area of conjugated conducting polymers, which is tissue engineering. Strategies used for the biocompatibility improvement of this class of polymers (including biomols.' entrapment or covalent grafting) and also the integrated novel technologies for smart scaffolds generation such as micropatterning, electrospinning, self-assembling are emphasized. These processing alternatives afford the electroconducting polymers nanostructures, the most appropriate forms of the materials that closely mimic the crit. features of the natural extracellular matrix. Due to their capability to electronically control a range of phys. and chem. properties, conducting polymers such as polyaniline, polypyrrole, and polythiophene and/or their derivs. and composites provide compatible substrates which promote cell growth, adhesion, and proliferation at the polymer-tissue interface through elec. stimulation. The activities of different types of cells on these materials are also presented in detail. Specific cell responses depend on polymers surface characteristics like roughness, surface free energy, topog., chem., charge, and other properties as elec. cond. or mech. actuation, which depend on the employed synthesis conditions. The biol. functions of cells can be dramatically enhanced by biomaterials with controlled organizations at the nanometer scale and in the case of conducting polymers, by the elec. stimulation. The advantages of using biocompatible nanostructures of conducting polymers (nanofibers, nanotubes, nanoparticles, and nanofilaments) in tissue engineering are also highlighted.
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Rivers, T. J.; Hudson, T. W.; Schmidt, C. E. Synthesis of a Novel, Biodegradable Electrically Conducting Polymer for Biomedical Applications. Adv. Funct. Mater. 2002, 12, 33, DOI: 10.1002/1616-3028(20020101)12:1<33::aid-adfm33>3.0.co;2-e
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Synthesis of a novel, biodegradable electrically conducting polymer for biomedical applications
Rivers, Tyrell J.; Hudson, Terry W.; Schmidt, Christine E.
Advanced Functional Materials (2002), 12 (1), 33-37CODEN: AFMDC6; ISSN:1616-301X. (Wiley-VCH Verlag GmbH)
The authors reported the synthesis and characterization of a novel biomaterial that possesses the unique properties of being both elec. conducting and biodegradable; and thus capable of electronic interfacing with tissue. This polymer was synthesized from conducting oligomers of pyrrole and thiophene that are connected together via degradable ester linkages. This polymer is conductive, degradable, and biocompatible.
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Huang, L.; Hu, J.; Lang, L.; Wang, X.; Zhang, P.; Jing, X.; Wang, X.; Chen, X.; Lelkes, P. I.; MacDiarmid, A. G. Synthesis and Characterization of Electroactive and Biodegradable ABA Block Copolymer of Polylactide and Aniline Pentamer. Biomaterials 2007, 28, 1741– 1751, DOI: 10.1016/j.biomaterials.2006.12.007
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Synthesis and characterization of electroactive and biodegradable ABA block copolymer of polylactide and aniline pentamer
Huang, Lihong; Hu, Jun; Lang, Le; Wang, Xin; Zhang, Peibiao; Jing, Xiabin; Wang, Xianhong; Chen, Xuesi; Lelkes, Peter I.; MacDiarmid, Alan G.; Wei, Yen
Biomaterials (2007), 28 (10), 1741-1751CODEN: BIMADU; ISSN:0142-9612. (Elsevier Ltd.)
A triblock copolymer PLA-b-AP-b-PLA (PAP) of polylactide (PLA) and aniline pentamer (AP) with the unique properties of being both electroactive and biodegradable is synthesized by coupling an electroactive carboxyl-capped AP with two biodegradable bi-hydroxyl-capped PLAs via a condensation reaction. Three different mol. wt. PAP copolymers are prepd. The PAP copolymers exhibit excellent electroactivity similar to the AP and polyaniline, which may stimulate cell proliferation and differentiation. The elec. cond. of the PAP2 copolymer film (∼5×10-6 S/cm) is in the semiconducting region. Transmission electron microscopic results suggest that there is microphase sepn. of the two block segments in the copolymer, which might contribute to the obsd. cond. The biodegrdn. and biocompatibility expts. in vitro prove the copolymer is biodegradable and biocompatible. Moreover, these new block copolymer shows good soly. in common org. solvents, leading to the system with excellent processibility. These biodegradable PAP copolymers with electroactive function thus possess the properties that would be potentially used as scaffold materials for neuronal or cardiovascular tissue engineering.
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Xie, M.; Wang, L.; Ge, J.; Guo, B.; Ma, P. X. Strong Electroactive Biodegradable Shape Memory Polymer Networks Based on Star-Shaped Polylactide and Aniline Trimer for Bone Tissue Engineering. ACS Appl. Mater. Interfaces 2015, 7, 6772– 6781, DOI: 10.1021/acsami.5b00191
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Strong Electroactive Biodegradable Shape Memory Polymer Networks Based on Star-Shaped Polylactide and Aniline Trimer for Bone Tissue Engineering
Xie, Meihua; Wang, Ling; Ge, Juan; Guo, Baolin; Ma, Peter X.
ACS Applied Materials & Interfaces (2015), 7 (12), 6772-6781CODEN: AAMICK; ISSN:1944-8244. (American Chemical Society)
Prepn. of functional shape memory polymer (SMP) for tissue engineering remains a challenge. Here the synthesis of strong electroactive shape memory polymer (ESMP) networks based on star-shaped polylactide (PLA) and aniline trimer (AT) is reported. Six-armed PLAs with various chain lengths were chem. crosslinked to synthesize SMP. After addn. of an electroactive AT segment into the SMP, ESMP was obtained. The polymers were characterized by 1H NMR, GPC, FT-IR, CV, DSC, DMA, tensile test, and degrdn. test. The SMP and ESMP exhibited strong mech. properties (modulus higher than GPa) and excellent shape memory performance: short recovery time (several seconds), high recovery ratio (over 94%), and high fixity ratio (almost 100%). Moreover, cyclic voltammetry test confirmed the electroactivity of the ESMP. The ESMP significantly enhanced the proliferation of C2C12 cells compared to SMP and linear PLA (control). In addn., the ESMP greatly improved the osteogenic differentiation of C2C12 myoblast cells compared to PH10 and PLA in terms of ALP enzyme activity, immunofluorescence staining, and relative gene expression by quant. real-time polymerase chain reaction (qRT-PCR). These intelligent SMPs and electroactive SMP with strong mech. properties, tunable degradability, good electroactivity, biocompatibility, and enhanced osteogenic differentiation of C2C12 cells show great potential for bone regeneration.
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Dong, R.; Zhao, X.; Guo, B.; Ma, P. X. Self-Healing Conductive Injectable Hydrogels with Antibacterial Activity as Cell Delivery Carrier for Cardiac Cell Therapy. ACS Appl. Mater. Interfaces 2016, 8, 17138– 17150, DOI: 10.1021/acsami.6b04911
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Self-Healing Conductive Injectable Hydrogels with Antibacterial Activity as Cell Delivery Carrier for Cardiac Cell Therapy
Dong, Ruonan; Zhao, Xin; Guo, Baolin; Ma, Peter X.
ACS Applied Materials & Interfaces (2016), 8 (27), 17138-17150CODEN: AAMICK; ISSN:1944-8244. (American Chemical Society)
Cell therapy is a promising strategy to regenerate cardiac tissue for myocardial infarction. Injectable hydrogels with cond. and self-healing ability are highly desirable as cell delivery vehicles for cardiac regeneration. Here, we developed self-healable conductive injectable hydrogels based on chitosan-graft-aniline tetramer (CS-AT) and dibenzaldehyde-terminated poly(ethylene glycol) (PEG-DA) as cell delivery vehicles for myocardial infarction. Self-healed electroactive hydrogels were obtained after mixing CS-AT and PEG-DA solns. at physiol. conditions. Rapid self-healing behavior was investigated by rheometer. Swelling behavior, morphol., mech. strength, electrochem., cond., adhesiveness to host tissue and antibacterial property of the injectable hydrogels were fully studied. Cond. of the hydrogels is ∼10-3 S·cm-1, which is quite close to native cardiac tissue. Proliferation of C2C12 myoblasts in the hydrogel showed its good biocompatibility. After injection, viability of C2C12 cells in the hydrogels showed no significant difference with that before injection. Two different cell types were successfully encapsulated in the hydrogels by self-healing effect. Cell delivery profile of C2C12 myoblasts and H9c2 cardiac cells showed a tunable release rate, and in vivo cell retention in the conductive hydrogels was also studied. S.c. injection and in vivo degrdn. of the hydrogels demonstrated their injectability and biodegradability. Together, these self-healing conductive biodegradable injectable hydrogels are excellent candidates as cell delivery vehicle for cardiac repair.
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Jia, X.; Chao, D.; Berda, E. B.; Pei, S.; Liu, H.; Zheng, T.; Wang, C. Fabrication of Electrochemically Responsive Surface Relief Diffraction Gratings Based on a Multifunctional Polyamide Containing Oligoaniline and Azo Groups. J. Mater. Chem. 2011, 21, 18317, DOI: 10.1039/c1jm14047g
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Guo, B.; Finne-Wistrand, A.; Albertsson, A.-C. Universal Two-Step Approach to Degradable and Electroactive Block Copolymers and Networks from Combined Ring-Opening Polymerization and Post-Functionalization via Oxidative Coupling Reactions. Macromolecules 2011, 44, 5227– 5236, DOI: 10.1021/ma2009595
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Universal Two-Step Approach to Degradable and Electroactive Block Copolymers and Networks from Combined Ring-Opening Polymerization and Post-Functionalization via Oxidative Coupling Reactions
Guo, Baolin; Finne-Wistrand, Anna; Albertsson, Ann-Christine
Macromolecules (Washington, DC, United States) (2011), 44 (13), 5227-5236CODEN: MAMOBX; ISSN:0024-9297. (American Chemical Society)
We present a universal strategy for the facile synthesis of degradable and electroactive block copolymers and organogels (DEBCGs) based on aniline oligomers and polyesters in a two-step approach, here exemplified by the prepn. of a series of DECBCGs based on aniline tetramer (AT) and poly(ε-caprolactone) (PCL). Polyesters with an aniline dimer (AD) segment were first obtained by controlled ring-opening polymn. (ROP) of ε-caprolactone initiated by the amine group of AD with or without 2,2-bis(ε-caprolactone-4-yl) propane (BCP). The postpolymn. modification via an oxidative coupling reaction between AD and a polyester was then used to form the electroactive segment AT in the copolymers or organogels. The mol. wt. and cond. of the block copolymers and organogels were controlled by the AT content. The chem. structure, electroactivity, and thermal properties of DEBCGs were investigated by FT-IR, NMR, SEC, UV, cyclic voltammetry, TGA, and DSC. Our general strategy for the synthesis of DECBCGs avoids the multiple step reactions and low efficiency involved in previous work.
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Guo, B.; Finne-Wistrand, A.; Albertsson, A.-C. Simple Route to Size-Tunable Degradable and Electroactive Nanoparticles from the Self-Assembly of Conducting Coil–Rod–Coil Triblock Copolymers. Chem. Mater. 2011, 23, 4045– 4055, DOI: 10.1021/cm201782v
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Lin, W.; Fu, Q.; Zhang, Y.; Huang, J. One-Pot Synthesis of ABC Type Triblock Copolymers via a Combination of “Click Chemistry” and Atom Transfer Nitroxide Radical Coupling Chemistry. Macromolecules 2008, 41, 4127– 4135, DOI: 10.1021/ma702404t
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One-Pot Synthesis of ABC Type Triblock Copolymers via a Combination of "Click Chemistry" and Atom Transfer Nitroxide Radical Coupling Chemistry
Lin, Wencheng; Fu, Qiang; Zhang, Yi; Huang, Junlian
Macromolecules (Washington, DC, United States) (2008), 41 (12), 4127-4135CODEN: MAMOBX; ISSN:0024-9297. (American Chemical Society)
A new strategy for one-pot synthesis of ABC type triblock copolymers via a combination of "click chem." and atom transfer nitroxide radical coupling (ATNRC) reaction was suggested, and poly(tert-Bu acrylate)-block-polystyrene-block-poly(ethylene oxide) (PtBA-PS-PEO) and poly(tert-Bu acrylate)-block-polystyrene-block-poly(ε-caprolactone) (PtBA-PS-PCL) were successfully prepd. by this method. The precursors with predetd. no.-av. mol. wt. and low polydispersity indexes, such as PS with α-alkyne and ω-bromine end groups, PtBA with azide end group, PEO and PCL with a 2,2,6,6-tetramethylpiperidine-1-oxyl end group, were directly prepd. by living polymn. technique using the compds. with corresponding functional groups as initiators, and no further modifications of the end groups were needed, except PtBA-N3. The coupling reaction between precursors was carried out in the CuBr/N,N,N',N'',N''-pentamethyldiethylenetriamine system with high efficiencies. The obtained polymers were characterized by FT-IR, 1H NMR, differential scanning calorimetry, and gel permeation chromatog. in detail.
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Guo, B.; Finne-Wistrand, A.; Albertsson, A.-C. Degradable and Electroactive Hydrogels with Tunable Electrical Conductivity and Swelling Behavior. Chem. Mater. 2011, 23, 1254– 1262, DOI: 10.1021/cm103498s
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Degradable and Electroactive Hydrogels with Tunable Electrical Conductivity and Swelling Behavior
Guo, Baolin; Finne-Wistrand, Anna; Albertsson, Ann-Christine
Chemistry of Materials (2011), 23 (5), 1254-1262CODEN: CMATEX; ISSN:0897-4756. (American Chemical Society)
Degradable elec. conducting hydrogels (DECHs), which combine the unique properties of degradable polymers and elec. conducting hydrogels, were synthesized by introducing biodegradable segments into conductive hydrogels. These DECHs were obtained by joining together the photopolymd. macromer acrylated poly(D,L-lactide)-poly(ethylene glycol)-poly(D,L-lactide) (AC-PLA-PEG-PLA-AC), glycidyl methacrylate (GMA), ethylene glycol dimethacrylate (EGDMA) network and aniline tetramer (AT) by the coupling reaction between AT and the GMA. The elec. cond. and swelling behavior of these DECHs were tuned by changing the AT content in the hydrogels, the crosslinking degree, and the environmental pH value. The good electroactivity and thermal stability of these hydrogels were demonstrated by UV-vis spectroscopy, cyclic voltammetry, and TGA tests. The chem. structure and morphol. of these polymers were characterized by NMR, FT-IR, SEC, and SEM. These hydrogels possessing both degradability and elec. cond. represent a new class of biomaterial and will lead to various new possibilities in biomedical applications.
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Borriello, A.; Guarino, V.; Schiavo, L.; Alvarez-Perez, M. A.; Ambrosio, L. Optimizing PANi Doped Electroactive Substrates as Patches for the Regeneration of Cardiac Muscle. J. Mater. Sci.: Mater. Med. 2011, 22, 1053– 1062, DOI: 10.1007/s10856-011-4259-x
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Optimizing PANi doped electroactive substrates as patches for the regeneration of cardiac muscle
Borriello, A.; Guarino, V.; Schiavo, L.; Alvarez-Perez, M. A.; Ambrosio, L.
Journal of Materials Science: Materials in Medicine (2011), 22 (4), 1053-1062CODEN: JSMMEL; ISSN:0957-4530. (Springer)
In scaffold aided regeneration of muscular tissue, composite materials are currently utilized as a temporary substrate to stimulate tissue formation by controlled electrochem. signals as well as continuous mech. stimulation until the regeneration processes are completed. Among them, composites from the blending of conductive (CPs) and biocompatible polymers are powerfully emerging as a successful strategy for the regeneration of myocardium due to their unique conductive and biol. recognition properties able to assure a more efficient electroactive stimulation of cells. Here, different composite substrates made of synthesized polyaniline (sPANi) and polycaprolactone (PCL) were investigated as platforms for cardiac tissue regeneration. Preliminary, a comparative anal. of substrates cond. performed on casted films endowed with synthesized polyaniline (sPANi) short fibers or blended with emeraldine base polyaniline (EBPANi) allows to study the attitude of charge transport, depending on the conducting filler amt., shape and spatial distribution. In particular, conductibility tests indicated that sPANi short fibers provide a more efficient transfer of elec. signal due to the spatial organization of electroactive needle-like phases up to form a percolative network. On the basis of this characterization, sPANi/PCL electrospun membranes have been also optimized to mimic either the morphol. and functional features of the cardiac muscle ECM. The presence of sPANi does not relevantly affect the fiber architecture as confirmed by SEM/image anal. investigation which shows a broader distribution of fibers with only a slight redn. of the av. fiber diam. from 7.1 to 6.4 μm. Meanwhile, biol. assays-evaluation of cell survival rate by MTT assay and immunostaining of sarcomeric α-actinin of cardiomyocytes-like cells-clearly indicate that conductive signals offered by PANi needles, promote the cardiogenic differentiation of hMSC into cardiomyocyte-like cells. These preliminary results concur to promise the development of electroactive biodegradable substrates able to efficiently stimulate the basic cell mechanisms, paving the way towards a new generation of synthetic patches for the support of the regeneration of damaged myocardium.
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Wang, H.-j.; Ji, L.-w.; Li, D.-f.; Wang, J.-Y. Characterization of Nanostructure and Cell Compatibility of Polyaniline Films with Different Dopant Acids. J. Phys. Chem. B 2008, 112, 2671– 2677, DOI: 10.1021/jp0750957
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Characterization of Nanostructure and Cell Compatibility of Polyaniline Films with Different Dopant Acids
Wang, Hua-jie; Ji, Li-wen; Li, Da-feng; Wang, Jin-Ye
Journal of Physical Chemistry B (2008), 112 (9), 2671-2677CODEN: JPCBFK; ISSN:1520-6106. (American Chemical Society)
Polyaniline (PANi) films were prepd. by direct polymg. deposition with four different kinds of acids as dopants or were prepd. by a casting method on the surface of a polytetrafluoroethylene substrate. The properties of PANi films were characterized using at. force microscopy, elec. cond. measurements, and water contact angle measurements. Unlike the casting PANi film, exptl. results indicated that the synthesized PANi films had a similar nanostructure as that of av. nanoparticles (approx. diam. of 30-50 nm). To investigate the potential usefulness of PANi films in biomedical applications, we also studied their biocompatibility through the adhesion and proliferation properties of PC-12 pheochromocytoma cells. All the films were found to be biocompatible and allowed cell attachment and proliferation. However, the synthesized films have a much higher ability for cell adhesion than the casting film. After 4 days of culture on different PANi films, the cells formed more confluent monolayers on the synthesized PANi films than on the casting films. These results demonstrate that the PANi films could be used to culture neurotic cells and that their surface architecture on the nanoscale may affect cell function such as attachment and proliferation.
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Bober, P.; Humpolíček, P.; Pacherník, J.; Stejskal, J.; Lindfors, T. Conducting Polyaniline Based Cell Culture Substrate for Embryonic Stem Cells and Embryoid Bodies. RSC Adv. 2015, 5, 50328– 50335, DOI: 10.1039/c5ra07504a
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Conducting polyaniline based cell culture substrate for embryonic stem cells and embryoid bodies
Bober, Patrycja; Humpolicek, Petr; Pachernik, Jiri; Stejskal, Jaroslav; Lindfors, Tom
RSC Advances (2015), 5 (62), 50328-50335CODEN: RSCACL; ISSN:2046-2069. (Royal Society of Chemistry)
In this work, thin films consisting of elec. conducting polyaniline (PANI) and poly(2-acrylamido-2-methyl-1-propanesulfonate) (PAMPSA) have been used as cell culture substrates for embryonic stem cells (ESC) and embryoid bodies (EMB). The PANI-PAMPSA films having fibrillar morphol. were electrochem. polymd. in a single-step by cyclic voltammetry from an aq. soln. contg. aniline and PAMPSA. UV-visible spectroscopy showed that the PANI films were elec. conducting still at pH 10. This makes them suitable for tissue engineering applications operating at physiol. pH, in contrast to the commonly used PANI hydrochloride films which loose their elec. cond. at pH ≥ 4. Our results reveal that the PANI-PAMPSA films allow only for limited ESC adhesion and growth. The inhibition of the EMB growth and adhesion on the PANI-PAMPSA surface in serum-free medium indicates that it can be used as a cell-selective substrate for the growth of only some specific differentiated EMB cell types.
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Strakosas, X.; Wei, B.; Martin, D. C.; Owens, R. M. Biofunctionalization of Polydioxythiophene Derivatives for Biomedical Applications. J. Mater. Chem. B 2016, 4, 4952– 4968, DOI: 10.1039/c6tb00852f
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Biofunctionalization of polydioxythiophene derivatives for biomedical applications
Strakosas, Xenofon; Wei, Bin; Martin, David C.; Owens, Roisin M.
Journal of Materials Chemistry B: Materials for Biology and Medicine (2016), 4 (29), 4952-4968CODEN: JMCBDV; ISSN:2050-7518. (Royal Society of Chemistry)
The polydioxythiophenes PEDOT and more recently ProDOT have emerged as champion materials in the field of org. bioelectronics, both in the domain of biosensing and also for integration with living cells (both in vitro and in vivo). Although polydioxythiophenes in their pristine forms have shown great promise for bioelectronics, in order to broaden the spectrum of applications, a biofunctionalization step is essential. In this review we summarise the methods that have been used thus far to biofunctionalize polydioxythiophenes in an effort to improve the biotic/abiotic interface. We provide an introduction to this class of materials, focusing particularly on the different methods of synthesis (chem. oxidative polymn., vapor phase polymn. or direct electrochem. polymn.) and discuss the implications of synthesis on biofunctionalization. Rather than provide an exhaustive review, we chose to highlight key examples of biofunctionalization techniques for polydioxythiophenes for specific biomedical applications. Finally, we conclude with a brief discussion of the importance of biofunctionalization methods in future bioelectronics applications, and some ideas for future directions in this field.
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Mantione, D.; del Agua, I.; Sanchez-Sanchez, A.; Mecerreyes, D. Poly(3,4-Ethylenedioxythiophene) (PEDOT) Derivatives: Innovative Conductive Polymers for Bioelectronics. Polymers 2017, 9, 354, DOI: 10.3390/polym9080354
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Poly(3,4-ethylenedioxythiophene) (PEDOT) derivatives: innovative conductive polymers for bioelectronics
Mantione, Daniele; del Agua, Isabel; Sanchez-Sanchez, Ana; Mecerreyes, David
Polymers (Basel, Switzerland) (2017), 9 (8), 354/1-354/21CODEN: POLYCK; ISSN:2073-4360. (MDPI AG)
A review. Poly(3,4-ethylenedioxythiophene)s are the conducting polymers (CP) with the biggest prospects in the field of bioelectronics due to their combination of characteristics (cond., stability, transparency and biocompatibility). The gold std. material is the com. available poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS). However, in order to well connect the two fields of biol. and electronics, PEDOT:PSS presents some limitations assocd. with its low (bio)functionality. In this review, we provide an insight into the synthesis and applications of innovative poly(ethylenedioxythiophene)-type materials for bioelectronics. First, we present a detailed anal. of the different synthetic routes to (bio)functional dioxythiophene monomer/polymer derivs. Second, we focus on the prepn. of PEDOT dispersions using different biopolymers and biomols. as dopants and stabilizers. To finish, we review the applications of innovative PEDOT-type materials such as biocompatible conducting polymer layers, conducting hydrogels, biosensors, selective detachment of cells, scaffolds for tissue engineering, electrodes for electrophysiol., implantable electrodes, stimulation of neuronal cells or pan-bio electronics.
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Povlich, L. K.; Cho, J. C.; Leach, M. K.; Corey, J. M.; Kim, J.; Martin, D. C. Synthesis, Copolymerization and Peptide-Modification of Carboxylic Acid-Functionalized 3,4-Ethylenedioxythiophene (EDOTacid) for Neural Electrode Interfaces. Biochim. Biophys. Acta, Gen. Subj. 2013, 1830, 4288– 4293, DOI: 10.1016/j.bbagen.2012.10.017
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Synthesis, copolymerization and peptide-modification of carboxylic acid-functionalized 3,4-ethylenedioxythiophene (EDOTacid) for neural electrode interfaces
Povlich, Laura K.; Cho, Jae Cheol; Leach, Michelle K.; Corey, Joseph M.; Kim, Jinsang; Martin, David C.
Biochimica et Biophysica Acta, General Subjects (2013), 1830 (9), 4288-4293CODEN: BBGSB3; ISSN:0304-4165. (Elsevier B.V.)
Conjugated polymers have been developed as effective materials for interfacing prosthetic device electrodes with neural tissue. Recent focus has been on the development of conjugated polymers that contain biol. components in order to improve the tissue response upon implantation of these electrodes. Carboxylic acid-functionalized 3,4-ethylenedioxythiophene (EDOTacid) monomer was synthesized in order to covalently bind peptides to the surface of conjugated polymer films. EDOTacid was copolymd. with EDOT monomer to form stable, elec. conductive copolymer films referred to as PEDOT-PEDOTacid. The peptide GGGGRGDS was bound to PEDOT-PEDOTacid to create peptide functionalized PEDOT films. The PEDOT-PEDOTacid-peptide films increased the adhesion of primary rat motor neurons between 3 and 9 times higher than controls, thus demonstrating that the peptide maintained its biol. activity. The EDOT-acid monomer can be used to create functionalized PEDOT-PEDOTacid copolymer films that can have controlled bioactivity. PEDOT-PEDOTacid-peptide films have the potential to control the behavior of neurons and vastly improve the performance of implanted electrodes. This article is part of a Special Issue entitled Org. Bioelectronics-Novel Applications in Biomedicine.
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Wei, B.; Liu, J.; Ouyang, L.; Kuo, C.-C.; Martin, D. C. Significant Enhancement of PEDOT Thin Film Adhesion to Inorganic Solid Substrates with EDOT-Acid. ACS Appl. Mater. Interfaces 2015, 7, 15388– 15394, DOI: 10.1021/acsami.5b03350
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Significant Enhancement of PEDOT Thin Film Adhesion to Inorganic Solid Substrates with EDOT-Acid
Wei, Bin; Liu, Jinglin; Ouyang, Liangqi; Kuo, Chin-Chen; Martin, David C.
ACS Applied Materials & Interfaces (2015), 7 (28), 15388-15394CODEN: AAMICK; ISSN:1944-8244. (American Chemical Society)
With its high cond., tunable surface morphol., relatively soft mech. response, high chem. stability, and excellent biocompatibility, poly(3,4-ethylenedioxythiophene) (PEDOT) has become a promising coating material for a variety of electronic biomedical devices. However, the relatively poor adhesion of PEDOT to inorg. metallic and semiconducting substrates still poses challenges for long-term applications. Here, we report that 2,3-dihydrothieno(3,4-b)(1,4)dioxine-2-carboxylic acid (EDOT-acid) significantly improves the adhesion between PEDOT thin films and inorg. solid electrodes. EDOT-acid mols. were chem. bonded onto activated oxide substrates via the chemisorption of the carboxylic groups. PEDOT was then polymd. onto the EDOT-acid modified substrates, forming covalently bonded coatings. The adsorption of EDOT-acid onto the electrode surfaces was characterized by cyclic voltammetry (CV), contact angle measurements, at. force microscopy, and XPS. The elec. properties of the subsequently coated PEDOT films were studied by electrochem. impedance spectroscopy and CV. An aggressive ultrasonication test confirmed the significantly improved adhesion and mech. stability of the PEDOT films on electrodes with EDOT-acid treatment over those without treatment.
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Mawad, D.; Artzy-Schnirman, A.; Tonkin, J.; Ramos, J.; Inal, S.; Mahat, M. M.; Darwish, N.; Zwi-Dantsis, L.; Malliaras, G. G.; Gooding, J. J. Electroconductive Hydrogel Based on Functional Poly(Ethylenedioxy Thiophene). Chem. Mater. 2016, 28, 6080– 6088, DOI: 10.1021/acs.chemmater.6b01298
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Electroconductive Hydrogel Based on Functional Poly(Ethylenedioxy Thiophene)
Mawad, Damia; Artzy-Schnirman, Arbel; Tonkin, Joanne; Ramos, Jose; Inal, Sahika; Mahat, Muzamir M.; Darwish, Nadim; Zwi-Dantsis, Limor; Malliaras, George G.; Gooding, J. Justin; Lauto, Antonio; Stevens, Molly M.
Chemistry of Materials (2016), 28 (17), 6080-6088CODEN: CMATEX; ISSN:0897-4756. (American Chemical Society)
Poly(ethylene dioxythiophene) with functional pendant groups bearing double bonds is synthesized and employed for the fabrication of electroactive hydrogels with advantageous characteristics; covalently crosslinked porous 3D scaffolds with notable swelling ratio, appropriate mech. properties, electroactive in physiol. conditions, and suitable for pro-liferation and differentiation of C2C12 cells. This is a new approach for the fabrication of conductive engineered constructs.
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Zhu, B.; Luo, S.-C.; Zhao, H.; Lin, H.-A.; Sekine, J.; Nakao, A.; Chen, C.; Yamashita, Y.; Yu, H.-h. Large Enhancement in Neurite Outgrowth on a Cell Membrane-Mimicking Conducting Polymer. Nat. Commun. 2014, 5, 4523, DOI: 10.1038/ncomms5523
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Large enhancement in neurite outgrowth on a cell membrane-mimicking conducting polymer
Zhu, Bo; Luo, Shyh-Chyang; Zhao, Haichao; Lin, Hsing-An; Sekine, Jun; Nakao, Aiko; Chen, Chi; Yamashita, Yoshiro; Yu, Hsiao-hua
Nature Communications (2014), 5 (), 4523CODEN: NCAOBW; ISSN:2041-1723. (Nature Publishing Group)
Although elec. stimulated neurite outgrowth on bioelectronic devices is a promising means of nerve regeneration, immunogenic scar formation can insulate electrodes from targeted cells and tissues, thereby reducing the lifetime of the device. Ideally, an electrode material capable of elec. interfacing with neurons selectively and efficiently would be integrated without being recognized by the immune system and minimize its response. Here we develop a cell membrane-mimicking conducting polymer possessing several attractive features. This polymer displays high resistance towards nonspecific enzyme/cell binding and recognizes targeted cells specifically to allow intimate elec. communication over long periods of time. Its low elec. impedance relays elec. signals efficiently. This material is capable to integrate biochem. and elec. stimulation to promote neural cellular behavior. Neurite outgrowth is enhanced greatly on this new conducting polymer; in addn., elec. stimulated secretion of proteins from primary Schwann cells can also occur on it.
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Wang, S.; Guan, S.; Wang, J.; Liu, H.; Liu, T.; Ma, X.; Cui, Z. Fabrication and Characterization of Conductive Poly (3,4-Ethylenedioxythiophene) Doped with Hyaluronic Acid/poly (L-Lactic Acid) Composite Film for Biomedical Application. J. Biosci. Bioeng. 2017, 123, 116– 125, DOI: 10.1016/j.jbiosc.2016.07.010
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Fabrication and characterization of conductive poly (3,4-ethylenedioxythiophene) doped with hyaluronic acid/poly (L-lactic acid) composite film for biomedical application
Wang, Shuping; Guan, Shui; Wang, Jing; Liu, Hailong; Liu, Tianqing; Ma, Xuehu; Cui, Zhanfeng
Journal of Bioscience and Bioengineering (2017), 123 (1), 116-125CODEN: JBBIF6; ISSN:1347-4421. (Society for Biotechnology, Japan)
Poly 3,4-ethylenedioxythiophene (PEDOT), a polythiophene deriv., has been proved to be modified by chem. process as biocompatible conductive polymer for biomedical applications. In this study, novel hyaluronic acid (HA)-doped PEDOT nanoparticles were synthesized by the method of chem. oxidative polymn., then conductive PEDOT-HA/poly(L-lactic acid) (PLLA) composite films were prepd. The physicochem. characteristics and biocompatibility of films were further investigated. FTIR, Raman and EDX anal. demonstrated that HA was successfully doped into PEDOT particles. Cyclic voltammograms indicated PEDOT-HA particles had favorable electrochem. stability. PEDOT-HA/PLLA films showed lower surface contact angle and faster degrdn. degree compared with PLLA films. Moreover, the cytotoxicity test of PEDOT-HA/PLLA films showed that neuron-like pheochromocytoma (PC12) cells adhered and spread well on the surface of PEDOT-HA/PLLA films and cell viability denoted by MTT assay had a significant increase. PEDOT-HA/PLLA films modified with laminin (LN) also exhibited an efficiently elongated cell morphol. obsd. by fluorescent microscope and metallog. microscope. Furthermore, PEDOT-HA/PLLA films were subjected to different current intensity to elucidate the effect of elec. stimulation (ES) on neurite outgrowth of PC12 cells. ES (0.5 mA, 2 h) significantly promoted neurite outgrowth with an av. value length of 122 ± 5 μm and enhanced the mRNA expression of growth-assocd. protein (GAP43) and synaptophysin (SYP) in PC12 cells when compared with other ES groups. These results suggest that PEDOT-HA/PLLA film combined with ES are conducive to cell growth and neurite outgrowth, indicating the conductive PEDOT-HA/PLLA film may be an attractive candidate with ES for enhancing nerve regeneration in nerve tissue engineering.
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Xu, H.; Holzwarth, J. M.; Yan, Y.; Xu, P.; Zheng, H.; Yin, Y.; Li, S.; Ma, P. X. Conductive PPY/PDLLA Conduit for Peripheral Nerve Regeneration. Biomaterials 2014, 35, 225– 235, DOI: 10.1016/j.biomaterials.2013.10.002
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Conductive PPY/PDLLA conduit for peripheral nerve regeneration
Xu, Haixing; Holzwarth, Jeremy M.; Yan, Yuhua; Xu, Peihu; Zheng, Hua; Yin, Yixia; Li, Shipu; Ma, Peter X.
Biomaterials (2014), 35 (1), 225-235CODEN: BIMADU; ISSN:0142-9612. (Elsevier Ltd.)
The significant drawbacks and lack of success assocd. with current methods to treat critically sized nerve defects have led to increased interest in neural tissue engineering. Conducting polymers show great promise due to their elec. properties, and in the case of polypyrrole (PPY), its cell compatibility as well. Thus, the goal of this study is to synthesize a conducting composite nerve conduit with PPY and poly(D, L-lactic acid) (PDLLA), assess its ability to support the differentiation of rat pheochromocytoma 12 (PC12) cells in vitro, and det. its ability to promote nerve regeneration in vivo. Different amts. of PPY (5%, 10%, and 15%) are used to synthesize the conduits resulting in different conductivities (5.65, 10.40, and 15.56 ms/cm, resp.). When PC12 cells are seeded on these conduits and stimulated with 100 mV for 2 h, there is a marked increase in both the percentage of neurite-bearing cells and the median neurite length as the content of PPY increased. More importantly, when the PPY/PDLLA nerve conduit was used to repair a rat sciatic nerve defect it performed similarly to the gold std. autologous graft. These promising results illustrate the potential that this PPY/PDLLA conducting composite conduit has for neural tissue engineering.
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Planellas, M.; Pérez-Madrigal, M. M.; del Valle, L. J.; Kobauri, S.; Katsarava, R.; Alemán, C.; Puiggalí, J. Microfibres of Conducting Polythiophene and Biodegradable Poly(ester Urea) for Scaffolds. Polym. Chem. 2015, 6, 925– 937, DOI: 10.1039/c4py01243g
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Microfibres of conducting polythiophene and biodegradable poly(ester urea) for scaffolds
Planellas, Marc; Perez-Madrigal, Maria M.; del Valle, Luis J.; Kobauri, Sophio; Katsarava, Ramaz; Aleman, Carlos; Puiggali, Jordi
Polymer Chemistry (2015), 6 (6), 925-937CODEN: PCOHC2; ISSN:1759-9962. (Royal Society of Chemistry)
Hybrid scaffolds constituted of a mixt. of conducting and biodegradable polymers are obtained by the electrospinning technique. Specifically, poly(3-thiophene Me acetate) (P3TMA) and a copolymer derived from L-leucine, which bears ester, urea and amide groups (PEU-co-PEA), have been employed. Both polymers were selected because of their intrinsic properties and their high soly. in org. solvents. The biodegradable polymer renders continuous and homogeneous microfibers under most of the electrospinning conditions tested, appearing to be an ideal carrier for the polythiophene deriv. A spontaneous phase sepn. has been obsd. for concd. solns. of PEU-co-PEA and P3TMA in chloroform-methanol mixts. An enriched dense phase results on the conducting polymer and can be successfully electrospun, giving rise to scaffolds with up to 90 wt% of P3TMA. Morphol. observations have indicated that continuous and regular microfibers are attained despite the high conducting polymer content. P3TMA presents a high doping level and leads to stable electrospun scaffolds by the simple addn. of a low percentage of a high mol. wt. carrier. The resulting scaffolds are practically amorphous and thermally stable, also presenting a pronounced electrochem. response and being electrochem. active. Thus, the formation of polarons and bipolarons at specific positions, the ability to exchange charge reversibly and the elec. stability of hybrid PEU-co-PEA/P3TMA electrospun scaffolds and P3TMA alone are practically the same.
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Huang, L.; Zhuang, X.; Hu, J.; Lang, L.; Zhang, P.; Wang, Y.; Chen, X.; Wei, Y.; Jing, X. Synthesis of Biodegradable and Electroactive Multiblock Polylactide and Aniline Pentamer Copolymer for Tissue Engineering Applications. Biomacromolecules 2008, 9, 850– 858, DOI: 10.1021/bm7011828
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Synthesis of biodegradable and electroactive multiblock polylactide and aniline pentamer copolymer for tissue engineering applications
Huang, Lihong; Zhuang, Xiuli; Hu, Jun; Lang, Le; Zhang, Peibiao; Wang, Yu; Chen, Xuesi; Wei, Yen; Jing, Xiabin
Biomacromolecules (2008), 9 (3), 850-858CODEN: BOMAF6; ISSN:1525-7797. (American Chemical Society)
To obtain one biodegradable and electroactive polymer as the scaffold for tissue engineering, the multiblock copolymer PLAAP was designed and synthesized with the condensation polymn. of hydroxyl-capped poly(L-lactide) (PLA) and carboxyl-capped aniline pentamer (AP). The PLAAP copolymer exhibited excellent electroactivity, soly., and biodegradability. At the same time, as one scaffold material, PLAAP copolymer possesses certain mech. properties with the tensile strength of 3 MPa, tensile Young's modulus of 32 MPa, and breaking elongation rate of 95%. We systematically studied the compatibility of PLAAP copolymer in vitro and proved that the electroactive PLAAP copolymer was innocuous, biocompatible, and helpful for the adhesion and proliferation of rat C6 cells. Moreover, the PLAAP copolymer stimulated by elec. signals was demonstrated as accelerating the differentiation of rat neuronal pheochromocytoma PC-12 cells. This biodegradable and electroactive PLAAP copolymer thus possessed the properties in favor of the long-time application in vivo as nerve repair scaffold materials in tissue engineering.
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Zotti, G.; Zecchin, S.; Schiavon, G.; Louwet, F.; Groenendaal, L.; Crispin, X.; Osikowicz, W.; Salaneck, W.; Fahlman, M. Electrochemical and XPS Studies toward the Role of Monomeric and Polymeric Sulfonate Counterions in the Synthesis, Composition, and Properties of Poly(3,4-Ethylenedioxythiophene). Macromolecules 2003, 36, 3337– 3344, DOI: 10.1021/ma021715k
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Electrochemical and XPS Studies toward the Role of Monomeric and Polymeric Sulfonate Counterions in the Synthesis, Composition, and Properties of Poly(3,4-ethylenedioxythiophene)
Zotti, G.; Zecchin, S.; Schiavon, G.; Louwet, F.; Groenendaal, L.; Crispin, X.; Osikowicz, W.; Salaneck, W.; Fahlman, M.
Macromolecules (2003), 36 (9), 3337-3344CODEN: MAMOBX; ISSN:0024-9297. (American Chemical Society)
Electrochem. prepd. poly(3,4-ethylenedioxythiophene) (PEDT) poly(styrene sulfonate) (PSS), produced from acidic (PSSH) and basic (PSSNa) PSS, were characterized by cyclic voltammetry CV, UV-vis spectroscopy, in situ cond., and XPS spectroscopy and compared with electrochem. prepd. PEDT/tosylate and chem. prepd. PEDT/PSS. The CV data shows that the polymer synthesis is strongly affected by the nucleophilic character of the counter-anion. Although CV and UV-vis spectroscopy show that the structure and d.p. (oligomeric, ca. 10 EDT units) of the PEDT backbone is the same for all polymers, XPS data provide clarification on different cond. obsd. for these materials (1 S cm-1 for PEDT/PSSNa to 400-450 S cm-1 for PEDT/tosylate) based on doping level and compn. The ratio between sulfonate and thiophene units in the polymer is an important factor; the higher the PEDT concn., the higher the cond. The XPS data also clarify the solvent-induced nanometer-scale segregation between PEDT/PSS and excess PSS particles, the often reported cond. enhancement of chem. prepd. PEDT/PSS upon treatment with polar solvents.
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MacDiarmid, A. G.; Zhou, Y.; Feng, J. Oligomers and Isomers: New Horizons in Poly-Anilines. Synth. Met. 1999, 100, 131– 140, DOI: 10.1016/s0379-6779(98)00164-7
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Oligomers and isomers: new horizons in poly-anilines
MacDiarmid, Alan G.; Zhou, Yao; Feng, Jing
Synthetic Metals (1999), 100 (1), 131-140CODEN: SYMEDZ; ISSN:0379-6779. (Elsevier Science S.A.)
The role of isomers in detg. the electronic, magnetic, optical, structural, and mech. properties of polyanilines, including polyaniline was studied. Known types of isomers, i.e., positional, cis/trans, rotational, and isomerization processes, some of which occur relatively slowly even at room temp. in soln. are described. Approaches for detg. the intrinsic properties of polyaniline by isolating the polymer preferably in one isomeric form or as a mixt. contg. a smaller than usual no. of different isomers are outlined.
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Elliott, B. J.; Ellis, W. W.; Luebben, S. D.; Sapp, S. A.; Chang, C.-H.; D’Sa, R. Electrically Conducting Materials from Branched End-Capping Intermediates. U.S. Patent 7,361,728 B1, 2004.
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MacDiarmid, A. G. Polyaniline and Polypyrrole: Where Are We Headed?. Synth. Met. 1997, 84, 27– 34, DOI: 10.1016/s0379-6779(97)80658-3
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Polyaniline and polypyrrole: where are we headed?
MacDiarmid, Alan G.
Synthetic Metals (1997), 84 (1-3), 27-34CODEN: SYMEDZ; ISSN:0379-6779. (Elsevier)
A review with 33 refs. The tremendous advances made during the past decade in the chem., electrochem., physics, theory and processing of polyaniline and polypyrrole and their derivs. provide a broad solid foundation for future studies and technol. applications. Selected examples of recent progress are illustrated by: (i) the synthesis of polyaniline oligomers and chiral polyaniline films, (ii) use of polyaniline in light-emitting devices, (iii) effect of substrate surface on properties of polyaniline and polypyrrole films deposited upon them, (i.v.) use of polypyrrole films in flexible, liq. crystal light valves, (v) prepn. of patterned polyaniline and polypyrrole films by microcontact printing and (vi) application of sol. polypyrrole in sensors for volatile org. compds.
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Avlyanov, J. K.; Min, Y.; MacDiarmid, A. G.; Epstein, A. J. Polyaniline: Conformational Changes Induced in Solution by Variation of Solvent and Doping Level. Synth. Met. 1995, 72, 65– 71, DOI: 10.1016/0379-6779(94)02318-s
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Polyaniline: conformational changes induced in solution by variation of solvent and doping level
Avlyanov, Jamshid K.; Min, Yonggang; MacDiarmid, Alan G.; Epstein, Arthur J.
Synthetic Metals (1995), 72 (1), 65-71CODEN: SYMEDZ; ISSN:0379-6779. (Elsevier)
The reduced viscosity of mixts. of polyaniline (emeraldine base, EB) and d, l-camphorsulfonic acid (HCSA) in solns. of m-cresol or chloroform (or in mixts. of these solvents) was investigated. Viscosity measurements as a function of (a) increasing m-cresol content in the mixed solvent for a fully protonated 'EBH+/CSA-' polymer, and (b) increasing protonation level of EB by increasing amts. of HCSA in m-cresol, indicate that the fully protonated polymer adopts a maximized expanded mol. conformation in a good solvent such as m-cresol. These results suggest that the greatly different conductivities obtained for 'EBH+/CSA-' films cast from m-cresol or chloroform solns. result primarily from their different mol. conformations in these solvents.
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da Silva, A. C.; Augusto, T.; Andrade, L. H.; de Torresi, S. I. C. One Pot Biocatalytic Synthesis of a Biodegradable Electroactive Macromonomer Based on 3,4-Ethylenedioxytiophene and Poly(L-Lactic Acid). Mater. Sci. Eng., C 2018, 83, 35– 43, DOI: 10.1016/j.msec.2017.09.007
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One pot biocatalytic synthesis of a biodegradable electroactive macromonomer based on 3,4-ethylenedioxytiophene and poly(L-lactic acid)
da Silva, Arua C.; Augusto, Tatiana; Andrade, Leandro H.; Cordoba de Torresi, Susana I.
Materials Science & Engineering, C: Materials for Biological Applications (2018), 83 (), 35-43CODEN: MSCEEE; ISSN:0928-4931. (Elsevier B.V.)
A novel electroactive macromonomer based on poly(L-lactic acid) (PLLA) with (3,4-ethylenedioxythiophene) (EDOT) functional end groups, was prepd. by a traditional approach of organometallic polymn. with stannous octanoate [Sn(oct2)] and enzymic polymn. using immobilized Candida antarctica Lipase B (CAL-B) and Amano lipase Pseudomonas cepacia(PS-IM), as catalysts. In the synthetic strategy, (2,3-dihydrothieno[3,4-b] dioxin-2-yl)methanol (EDOT-OH) was used to initiate the ring opening polymn. of lactide to yield PLLA with EDOT end group. All macromonomers (EDOT-PLLA) were characterized by 1H and 13C RMN, MALDI-TOF, GPC and EDX. Moreover, ICP-OES anal. showed the presence of Sn traces in the material synthesized by the traditional approach, but that pathway led to macromonomers with higher mol. wt. while the enzymic route led to completely metal-free macromonomers with medium and lower mol. wts. Also, electrochem. and chem. polymn. of EDOT-PLLA were tested showing that it is possible to prep. degradable conducting polymers based on poly(3,4-ethylenedioxythiphene) (PEDOT). The biocatalytic synthesis is a very promising and environmental friendly pathway for the prepn. of biodegradable materials for short time applications.
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Betzel, C.; Singh, T. P.; Visanji, M.; Peters, K.; Fittkau, S.; Saenger, W.; Wilson, K. S. Structure of the Complex of Proteinase K with a Substrate Analogue Hexapeptide Inhibitor at 2.2-A Resolution. J. Biol. Chem. 1993, 268, 15854– 15858
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CNT Induced β-Phase in Polylactide: Unique Crystallization, Biodegradation, and Biocompatibility
Singh, Narendra K.; Singh, Sunil K.; Dash, Debabrata; Gonugunta, Prasad; Misra, Manjusri; Maiti, Pralay
Journal of Physical Chemistry C (2013), 117 (19), 10163-10174CODEN: JPCCCK; ISSN:1932-7447. (American Chemical Society)
The effect of multi-walled carbon nanotube (MWCNT) on the crystal structure, unique crystn., mech. behavior, enzymic degrdn., and significant improvement in biocompatibility of polylactide (PLA) nanohybrid has been reported. Functionalization of carbon nanotube using stearyl alc. has been carried out and has been confirmed through FTIR and Raman spectroscopy. PLA nanohybrids have been synthesized using functionalized and neat MWCNT through soln. route, and the improved level of dispersion of MWCNT has been achieved in PLA matrix. High-magnification transmission electron microscope images indicate the unique adsorption of PLA chain leading to the crystn. of β-phase structure on the surface of the functionalized MWCNT against the usual crystd. α-form of pure PLA. The presence of β phase in nanohybrids has been confirmed through electron diffraction pattern, differential scanning calorimetry thermograms, and X-ray diffraction patterns. The improved and diverse mech., thermal properties, and crystn. kinetics have been explored with the special emphasis on the relaxation behavior of β phase in dynamic mech. anal. The cause of these developments has been appraised from the interaction point of view as calcd. from the interaction parameter (χ) using melting-point depression technique. The rate of biodegrdn. has been studied in detail with plausible mechanism in Proteinase K enzyme media showing their specificity and tuning of biodegrdn. rate followed by their optimization. For biomedical applications, the effect of pure polymer and nanohybrids on circulating blood cells has been evaluated in detail, and the hemocompatible nature of the nanohybrids has been revealed, suppressing the cellular toxicity of MWCNT.
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Specificity of proteinase K from Tritirachium album for synthetic peptides
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Agricultural and Biological Chemistry (1975), 39 (7), 1489-92CODEN: ABCHA6; ISSN:0002-1369.
The specificity of proteinase K from T. Album Limber was detd. using various synthetic peptide substrates. The esterase activity against N-acylated amino acid esters indicated that the enzyme is primarily specific against aromatic or hydrophobic amino acid residues on the CO2H side of the cleavage point. The effect of neighboring amino acid residues on hydrolysis was also studied using peptide esters or other compds., which showed that the enzyme activity is markedly promoted by elongating the peptide chain on the N-terminal side of the cleavage point. Thus, peptide chloromethyl ketone derivatives such as Z-Ala-Gly-PheCH2Cl inactivated the enzyme activity markedly.
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Control of Neural Stem Cell Adhesion and Density by an Electronic Polymer Surface Switch
Salto, Carmen; Saindon, Emilien; Bolin, Maria; Kanciurzewska, Anna; Fahlman, Mats; Jager, Edwin W. H.; Tengvall, Pentti; Arenas, Ernest; Berggren, Magnus
Langmuir (2008), 24 (24), 14133-14138CODEN: LANGD5; ISSN:0743-7463. (American Chemical Society)
Adhesion is an essential parameter for stem cells. It regulates the overall cell d. along the carrying surface, which further dictates the differentiation scheme of stem cells toward a more matured and specified population as well as tissue. Electronic control of the seeding d. of neural stem cells (c17.2) is here reported. Thin electrode films of poly(3,4-ethylenedioxythiophene) (PEDOT):Tosylate were manufd. along the floor of cell growth dishes. As the oxidn. state of the conjugated polymer electrodes was controlled, the seeding d. could be varied by a factor of 2. Along the oxidized PEDOT:Tosylate-electrodes, a relatively lower d. of, and less tightly bonded, human serum albumin (HSA) was obsd. as compared to reduced electrodes. The authors found that this favors adhesion of the specific stem cells studied. Surface anal. expts., such as photoelectron spectroscopy, and water contact angle measurements, were carried out to investigate the mechanisms responsible for the electronic control of the seeding d. of the c17.2 neural stem cells. Further, the authors' findings may provide an opening for electronic control of stem cell differentiation.
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Li, N.; Zhang, Q.; Gao, S.; Song, Q.; Huang, R.; Wang, L.; Liu, L.; Dai, J.; Tang, M.; Cheng, G. Three-Dimensional Graphene Foam as a Biocompatible and Conductive Scaffold for Neural Stem Cells. Sci. Rep. 2013, 3, 1604, DOI: 10.1038/srep01604
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Three-dimensional graphene foam as a biocompatible and conductive scaffold for neural stem cells
Li, Ning; Zhang, Qi; Gao, Song; Song, Qin; Huang, Rong; Wang, Long; Liu, Liwei; Dai, Jianwu; Tang, Mingliang; Cheng, Guosheng
Scientific Reports (2013), 3 (), 1604, 6 pp.CODEN: SRCEC3; ISSN:2045-2322. (Nature Publishing Group)
Neural stem cell (NSC) based therapy provides a promising approach for neural regeneration. For the success of NSC clin. application, a scaffold is required to provide 3-dimensional (3D) cell growth microenvironments and appropriate synergistic cell guidance cues. Here, the authors report the first utilization of graphene foam, a 3D porous structure, as a novel scaffold for NSCs in vitro. It was found that 3-dimensional graphene foams (3D-GFs) can not only support NSC growth, but also keep cell at an active proliferation state with upregulation of Ki67 expression than that of 2-dimensional graphene films. Meanwhile, phenotypic anal. indicated that 3D-GFs can enhance the NSC differentiation towards astrocytes and esp. neurons. Furthermore, a good elec. coupling of 3D-GFs with differentiated NSCs for efficient elec. stimulation was obsd. The authors' findings implicate 3D-GFs could offer a powerful platform for NSC research, neural tissue engineering and neural prostheses.
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Protein adsorption data for human serum albumin, lysozyme, and α-lactalbumin on polystyrene are interpreted using thermodn. arguments. Energetic and entropic contributions from the major subprocesses that constitute the overall adsorption process are presented.
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Yeung, T.; Gilbert, G. E.; Shi, J.; Silvius, J.; Kapus, A.; Grinstein, S. Membrane Phosphatidylserine Regulates Surface Charge and Protein Localization. Science 2008, 319, 210– 213, DOI: 10.1126/science.1152066
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Membrane Phosphatidylserine Regulates Surface Charge and Protein Localization
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Science (Washington, DC, United States) (2008), 319 (5860), 210-213CODEN: SCIEAS; ISSN:0036-8075. (American Association for the Advancement of Science)
Electrostatic interactions with neg. charged membranes contribute to the subcellular targeting of proteins with polybasic clusters or cationic domains. Although the anionic phospholipid phosphatidylserine is comparatively abundant, its contribution to the surface charge of individual cellular membranes is unknown, partly because of the lack of reagents to analyze its distribution in intact cells. We developed a biosensor to study the subcellular distribution of phosphatidylserine and found that it binds the cytosolic leaflets of the plasma membrane, as well as endosomes and lysosomes. The neg. charge assocd. with the presence of phosphatidylserine directed proteins with moderately pos. charge to the endocytic pathway. More strongly cationic proteins, normally assocd. with the plasma membrane, relocalized to endocytic compartments when the plasma membrane surface charge decreased on calcium influx.
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White, G.; Lovinger, D. M.; Weight, F. F. Transient Low-Threshold Ca2+ Current Triggers Burst Firing through an Afterdepolarizing Potential in an Adult Mammalian Neuron. Proc. Natl. Acad. Sci. U.S.A. 1989, 86, 6802– 6806, DOI: 10.1073/pnas.86.17.6802
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Monteith, Gregory R.; McAndrew, Damara; Faddy, Helen M.; Roberts-Thomson, Sarah J.
Nature Reviews Cancer (2007), 7 (7), 519-530CODEN: NRCAC4; ISSN:1474-175X. (Nature Publishing Group)
A review. Ca2+ is a ubiquitous cellular signal. Altered expression of specific Ca2+ channels and pumps are characterizing features of some cancers. The ability of Ca2+ to regulate both cell death and proliferation, combined with the potential for pharmacol. modulation, offers the opportunity for a set of new drug targets in cancer. However, the ubiquity of the Ca2+ signal is often mistakenly presumed to thwart the specific therapeutic targeting of proteins that transport Ca2+. This review presents evidence to the contrary and addresses the question: which Ca2+ channels and pumps should be targeted.
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Isaksson, J.; Kjäll, P.; Nilsson, D.; Robinson, N.; Berggren, M.; Richter-Dahlfors, A. Electronic Control of Ca2+ Signalling in Neuronal Cells Using an Organic Electronic Ion Pump. Nat. Mater. 2007, 6, 673– 679, DOI: 10.1038/nmat1963
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Electronic control of Ca2+ signaling in neuronal cells using an organic electronic ion pump
Isaksson, Joakim; Kjaell, Peter; Nilsson, David; Robinson, Nathaniel; Berggren, Magnus; Richter-Dahlfors, Agneta
Nature Materials (2007), 6 (9), 673-679CODEN: NMAACR; ISSN:1476-1122. (Nature Publishing Group)
Cells and tissues use finely regulated ion fluxes for their intra- and intercellular communication. Technologies providing spatial and temporal control for studies of such fluxes are however, limited. We have developed an electrophoretic ion pump made of poly(3,4-ethylenedioxythiophene) doped with poly(styrene sulfonate) (PEDOT:PSS) to mediate electronic control of the ion homeostasis in neurons. Ion delivery from a source reservoir to a receiving electrolyte via a PEDOT:PSS thin-film channel was achieved by electronic addressing. Ions are delivered in high quantities at an assocd. on/off ratio exceeding 300. This induces physiol. signaling events that can be recorded at the single-cell level. Furthermore, miniaturization of the device to a 50-μm-wide channel allows for stimulation of individual cells. As this technol. platform allows for electronic control of ion signaling in individual cells with proper spatial and temporal resoln., it will be useful in further studies of communication in biol. systems.
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Taylor, A. C.; González, C. H.; Miller, B. S.; Edgington, R. J.; Ferretti, P.; Jackman, R. B. Surface Functionalisation of Nanodiamonds for Human Neural Stem Cell Adhesion and Proliferation. Sci. Rep. 2017, 7, 7307, DOI: 10.1038/s41598-017-07361-y
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Surface functionalisation of nanodiamonds for human neural stem cell adhesion and proliferation
Taylor Alice C; Miller Benjamin S; Edgington Robert J; Jackman Richard B; Gonzalez Citlali Helenes; Ferretti Patrizia
Scientific reports (2017), 7 (1), 7307 ISSN:.
Biological systems interact with nanostructured materials on a sub-cellular level. These interactions may govern cell behaviour and the precise control of a nanomaterial's structure and surface chemistry allow for a high degree of tunability to be achieved. Cells are surrounded by an extra-cellular matrix with nano-topographical properties. Diamond based materials, and specifically nanostructured diamond has attracted much attention due to its extreme electrical and mechanical properties, chemical inertness and biocompatibility. Here the interaction of nanodiamond monolayers with human Neural Stem Cells (hNSCs) has been investigated. The effect of altering surface functionalisation of nanodiamonds on hNSC adhesion and proliferation has shown that confluent cellular attachment occurs on oxygen terminated nanodiamonds (O-NDs), but not on hydrogen terminated nanodiamonds (H-NDs). Analysis of H and O-NDs by Atomic Force Microscopy, contact angle measurements and protein adsorption suggests that differences in topography, wettability, surface charge and protein adsorption of these surfaces may underlie the difference in cellular adhesion of hNSCs reported here.
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Gao, M.; Wang, Y.; Yi, Q.; Su, Y.; Sun, P.; Wang, X.; Zhao, J.; Zou, G. A Novel Solid-State Electrolyte Based on a Crown Ether Lithium Salt Complex. J. Mater. Chem. A 2015, 3, 20541– 20546, DOI: 10.1039/c5ta04933d
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A novel solid-state electrolyte based on a crown ether lithium salt complex
Gao, Minda; Wang, Yun; Yi, Qinghua; Su, Ying; Sun, Pengfei; Wang, Xiangguo; Zhao, Jie; Zou, Guifu
Journal of Materials Chemistry A: Materials for Energy and Sustainability (2015), 3 (41), 20541-20546CODEN: JMCAET; ISSN:2050-7496. (Royal Society of Chemistry)
A novel crown ether lithium salt complex [Li∈12-C-4][I] has been designed, synthesized and characterized. The thermal properties of the [Li∈12-C-4][I] based solid-state electrolytes were also investigated in detail. The particular trapping ability of 12-crown-4 to Li+ can obviously reduce the cation-anion (Li+-I-) interaction and hence facilitate favorable elec. properties of the solid-state electrolytes. Therefore, [Li∈12-C-4][I] represents ionic cond. of 3.93 × 10-5 and 1.53 × 10-4 S cm-1 at 25 and 80 °C, resp. Further addn. of the ionic liq. 1-propyl-3-methylimidazolium iodine as a crystal growth inhibitor can effectively suppress the crystn. of the complex for more amorphous and smoother regions, which are much more conducive towards higher ion cond. by the segmental motion of mol. chains. For application, the resulting device showed a power conversion efficiency of 5% and displayed excellent long-term stability. These results offer us more opportunities to explore simple and novel solid-state electrolytes for energy storage and conversion.
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The ORCA program system
Neese, Frank
Wiley Interdisciplinary Reviews: Computational Molecular Science (2012), 2 (1), 73-78CODEN: WIRCAH; ISSN:1759-0884. (Wiley-Blackwell)
A review. ORCA is a general-purpose quantum chem. program package that features virtually all modern electronic structure methods (d. functional theory, many-body perturbation and coupled cluster theories, and multireference and semiempirical methods). It is designed with the aim of generality, extendibility, efficiency, and user friendliness. Its main field of application is larger mols., transition metal complexes, and their spectroscopic properties. ORCA uses std. Gaussian basis functions and is fully parallelized. The article provides an overview of its current possibilities and documents its efficiency.
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Perdew, John P.; Burke, Kieron; Ernzerhof, Matthias
Physical Review Letters (1996), 77 (18), 3865-3868CODEN: PRLTAO; ISSN:0031-9007. (American Physical Society)
Generalized gradient approxns. (GGA's) for the exchange-correlation energy improve upon the local spin d. (LSD) description of atoms, mols., and solids. We present a simple derivation of a simple GGA, in which all parameters (other than those in LSD) are fundamental consts. Only general features of the detailed construction underlying the Perdew-Wang 1991 (PW91) GGA are invoked. Improvements over PW91 include an accurate description of the linear response of the uniform electron gas, correct behavior under uniform scaling, and a smoother potential.
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Weigend, F.; Ahlrichs, R. Balanced Basis Sets of Split Valence, Triple Zeta Valence and Quadruple Zeta Valence Quality for H to Rn: Design and Assessment of Accuracy. Phys. Chem. Chem. Phys. 2005, 7, 3297– 3305, DOI: 10.1039/b508541a
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Balanced basis sets of split valence, triple zeta valence and quadruple zeta valence quality for H to Rn: Design and assessment of accuracy
Weigend, Florian; Ahlrichs, Reinhart
Physical Chemistry Chemical Physics (2005), 7 (18), 3297-3305CODEN: PPCPFQ; ISSN:1463-9076. (Royal Society of Chemistry)
Gaussian basis sets of quadruple zeta valence quality for Rb-Rn are presented, as well as bases of split valence and triple zeta valence quality for H-Rn. The latter were obtained by (partly) modifying bases developed previously. A large set of more than 300 mols. representing (nearly) all elements-except lanthanides-in their common oxidn. states was used to assess the quality of the bases all across the periodic table. Quantities investigated were atomization energies, dipole moments and structure parameters for Hartree-Fock, d. functional theory and correlated methods, for which we had chosen Moller-Plesset perturbation theory as an example. Finally recommendations are given which type of basis set is used best for a certain level of theory and a desired quality of results.
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Grimme, S.; Ehrlich, S.; Goerigk, L. Effect of the Damping Function in Dispersion Corrected Density Functional Theory. J. Comput. Chem. 2011, 32, 1456– 1465, DOI: 10.1002/jcc.21759
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Effect of the damping function in dispersion corrected density functional theory
Grimme, Stefan; Ehrlich, Stephan; Goerigk, Lars
Journal of Computational Chemistry (2011), 32 (7), 1456-1465CODEN: JCCHDD; ISSN:0192-8651. (John Wiley & Sons, Inc.)
It is shown by an extensive benchmark on mol. energy data that the math. form of the damping function in DFT-D methods has only a minor impact on the quality of the results. For 12 different functionals, a std. "zero-damping" formula and rational damping to finite values for small interat. distances according to Becke and Johnson (BJ-damping) has been tested. The same (DFT-D3) scheme for the computation of the dispersion coeffs. is used. The BJ-damping requires one fit parameter more for each functional (three instead of two) but has the advantage of avoiding repulsive interat. forces at shorter distances. With BJ-damping better results for nonbonded distances and more clear effects of intramol. dispersion in four representative mol. structures are found. For the noncovalently-bonded structures in the S22 set, both schemes lead to very similar intermol. distances. For noncovalent interaction energies BJ-damping performs slightly better but both variants can be recommended in general. The exception to this is Hartree-Fock that can be recommended only in the BJ-variant and which is then close to the accuracy of cor. GGAs for non-covalent interactions. According to the thermodn. benchmarks BJ-damping is more accurate esp. for medium-range electron correlation problems and only small and practically insignificant double-counting effects are obsd. It seems to provide a phys. correct short-range behavior of correlation/dispersion even with unmodified std. functionals. In any case, the differences between the two methods are much smaller than the overall dispersion effect and often also smaller than the influence of the underlying d. functional. © 2011 Wiley Periodicals, Inc.; J. Comput. Chem., 2011.
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Abstract
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Scheme 1
Scheme 1. (A) Synthesis of Electroactive Macromonomer EDOT–PDLLA, (B) Synthesis of Conducting and Biodegradable Copolymer PEDOT-co-PDLLA, and (C) Structural Representation of Copolymer with Charge on Conducting Backbone of PEDOT and Branched PDLLA Chains
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Figure 1
Figure 1. DFT/PBE-D3/def2-TZV optimized structures of EDOT–PDLLA macromonomers. Arrows indicate the most important contributing vibrations in the calculated band at (A) 766.88 and (B) 872 cm^–1.
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Figure 2
Figure 2. j/E potentiodynamic profiles of bare glassy carbon (black), EDOT–PDLLA (gray), and conducting biodegradable copolymer films of PEDOT-co-PDLLA 1:05 (red), 1:25 (green), and 1:50 (blue) in phosphate buffer electrolytic solution. v = 0.01 V s^–1.
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Scheme 2
Scheme 2. (A) Biodegradation Reaction and (B) Physical Aspects of PEDOT-co-PDLLA Films before and after 35 Days of Biodegradation Assay
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Figure 3
Figure 3. Biodegradation profiles of EDOT–PDLLA (black) PEDOT-co-PDLLA 1:05 (red), 1:25 (green), and 1:50 (blue) at 37 °C and 60 rpm.
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Figure 4
Figure 4. Proliferation and viability of ESCs on PEDOT-co-PDLLA CPs. Polymeric substrates with different compositions were tested against the control (traditional polystyrene plate), on which the cells were cultured for 24 h. (A) Optical microscopy images, calibration bar: 400 μm; (B) total count of cells grown on the polymer substrates; (C) percentage of viable cells shown as mean values ± SD; *P < 0.05.
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Figure 5
Figure 5. Adhesion and migration of NPCs from EBs on PEDOT-co-PDLLA CPs. Polymeric substrates for cell culture with different compositions were tested against the commercial plastic dish (control), to which the EBs adhered and the peripheral cells migrated. (A) Phase-contrast optical microscopy representative images of the EBs after 24 h of culture, with a calibration bar corresponding to 200 μm; (B) numbers of EBs adhered to the respective polymeric substrates; (C) mean ratio of the migration halo normalized by the respective area of each EB. Data are reported as mean values ± SD; *P < 0.05, **P < 0.01.
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Figure 6
Figure 6. Phase contrast microscopy images of ESCs after 7 days of neural differentiation on PEDOT-based scaffolds. Scale bar: 400 μm.
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Figure 7
Figure 7. Characterization of E14.tg2a ESC neural differentiation on a commercial plastic plate (control) and on PEDOT:PDLLA conductive polymers at proportions of 1:50, 1:25, and 1:05. Immunostaining for young neurons with anti-βIII tubulin (red) after 7 days from the beginning of the neural differentiation process. Immunostaining for mature neurons with anti-MAP2 (green) and glial cells with anti-S100β (red) after 14 days. Cell nuclei were stained with DAPI (blue). Scale bar: 100 μm.
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Figure 8
Figure 8. Quantification of neuronal-differentiated ESCs following anti-MAP-2 staining by StrataQuest analysis software (TissueGnostics). Images of phase-contrast and DAPI and Alexa488 fluorescent channels were overlaid (column 1); migration halo analysis by combining and processing images of DAPI and phase-contrast ROI (column 2); measurement of the total lengths of anti-MAP2-tagged neurites (column 3).
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  Balguid, Angelique; Mol, Anita; van Marion, Mieke H.; Bank, Ruud A.; Bouten, Carlijn V. C.; Baaijens, Frank P. T.
  Tissue Engineering, Part A (2009), 15 (2), 437-444CODEN: TEPAB9; ISSN:1937-3341. (Mary Ann Liebert, Inc.)
  Despite the attractive features of nanofibrous scaffolds for cell attachment in tissue-engineering (TE) applications, impeded cell ingrowth has been reported in electrospun scaffolds. Previous findings have shown that the scaffold can function as a sieve, keeping cells on the scaffold surface, and that cell migration into the scaffold does not occur in time. Because fiber diam. is directly related to the pore size of an electrospun scaffold, the objective of this study was to systematically evaluate how cell delivery can be optimized by tailoring the fiber diam. of electrospun poly(.vepsiln.-caprolactone) (PCL) scaffolds. Five groups of electrospun PCL scaffolds with increasing av. fiber diams. (3.4-12.1 μm) were seeded with human venous myofibroblasts. Cell distribution was analyzed after 3 days of culture. Cell penetration increased proportionally with increasing fiber diam. Unobstructed delivery of cells was obsd. exclusively in the scaffold with the largest fiber diam. (12.1 μm). This scaffold was subsequently evaluated in a 4-wk TE expt. and compared with a poly(glycolic acid)-poly(4-hydroxybutyrate) scaffold, a std. scaffold used successfully in cardiovascular tissue engineering applications. The PCL constructs showed homogeneous tissue formation and sufficient matrix deposition. In conclusion, fiber diam. is a crucial parameter to allow for homogeneous cell delivery in electrospun scaffolds. The optimal electrospun scaffold geometry, however, is not generic and should be adjusted to cell size.
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9. 9
  Riboldi, S. A.; Sampaolesi, M.; Neuenschwander, P.; Cossu, G.; Mantero, S. Electrospun Degradable Polyesterurethane Membranes: Potential Scaffolds for Skeletal Muscle Tissue Engineering. Biomaterials 2005, 26, 4606– 4615, DOI: 10.1016/j.biomaterials.2004.11.035
  9
  Electrospun degradable polyesterurethane membranes: potential scaffolds for skeletal muscle tissue engineering
  Riboldi, Stefania A.; Sampaolesi, Maurilio; Neuenschwander, Peter; Cossu, Giulio; Mantero, Sara
  Biomaterials (2005), 26 (22), 4606-4615CODEN: BIMADU; ISSN:0142-9612. (Elsevier Ltd.)
  Skeletal muscle tissue engineering represents an attractive approach to overcome problems assocd. with autologous transfer of muscle tissue and provides a valid alternative in muscle regeneration enhancement. The aim of this study was to investigate the suitability, as scaffold for skeletal muscle tissue engineering, of a known biodegradable block copolymer (DegraPol) processed by electrospinning in the novel form of microfibrous membranes. Scaffolds were characterized with ref. to their morphol., degradative and mech. properties. Subsequently, cell viability, adhesion and differentiation on coated and uncoated DegraPol slides were investigated using line cells (C2C12 and L6) and primary human satellite cells (HSCs). The membranes exhibited absence of toxic residuals and satisfactory mech. properties (linear elastic behavior up to 10% deformation, E modulus in the order of magnitude of MPa). A promising cellular response was also found in preliminary expts.: both line cells and HSCs adhered, proliferated and fused on differently coated electrospun membranes. Pos. staining for myosin heavy chain expression indicated that differentiation of C2C12 multinucleated cells occurred within the porous elastomeric substrate. Together the results of this study provide significant evidence of the suitability of electrospun DegraPol membranes as scaffolds for skeletal muscle tissue engineering and that they represent a promising alternative to scaffolds currently used in this field.
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10. 10
  Kim, B.-S.; Nikolovski, J.; Bonadio, J.; Smiley, E.; Mooney, D. J. Engineered Smooth Muscle Tissues: Regulating Cell Phenotype with the Scaffold. Exp. Cell Res. 1999, 251, 318– 328, DOI: 10.1006/excr.1999.4595
  10
  Engineered Smooth Muscle Tissues: Regulating Cell Phenotype with the Scaffold
  Kim, Byung-Soo; Nikolovski, Janeta; Bonadio, Jeffrey; Smiley, Elizabeth; Mooney, David J.
  Experimental Cell Research (1999), 251 (2), 318-328CODEN: ECREAL; ISSN:0014-4827. (Academic Press)
  Culturing cells on three-dimensional, biodegradable scaffolds may create tissues suitable either for reconstructive surgery applications or as novel in vitro model systems. In this study, we have tested the hypothesis that the phenotype of smooth muscle cells (SMCs) in three-dimensional, engineered tissues is regulated by the chem. of the scaffold material. Specifically, we have directly compared cell growth and patterns of extracellular matrix (ECM) (e.g., elastin and collagen) gene expression on two types of synthetic polymer scaffolds and type I collagen scaffolds. The growth rates of SMCs on the synthetic polymer scaffolds were significantly higher than on type I collagen sponges. The rate of elastin prodn. by SMCs on polyglycolic acid (PGA) scaffolds was 3.5 ± 1.1-fold higher than that on type I collagen sponges on Day 11 of culture. In contrast, the collagen prodn. rate on type I collagen sponges was 3.3 ± 1.1-fold higher than that on PGA scaffolds. This scaffold-dependent switching between elastin and collagen gene expression was confirmed by Northern blot anal. The finding that the scaffold chem. regulates the phenotype of SMCs independent of the scaffold phys. form was confirmed by culturing SMCs on two-dimensional films of the scaffold materials. It is likely that cells adhere to these scaffolds via different ligands, as the major protein adsorbed from the serum onto synthetic polymers was vitronectin, whereas fibronectin and vitronectin were present at high d. on type I collagen sponges. In summary, this study demonstrates that three-dimensional smooth muscle-like tissues can be created by culturing SMCs on three-dimensional scaffolds, and that the phenotype of the SMCs is strongly regulated by the scaffold chem. These engineered tissues provide novel, three-dimensional models to study cellular interaction with ECM in vitro. (c) 1999 Academic Press.
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11. 11
  Xu, C. Aligned Biodegradable Nanofibrous Structure: A Potential Scaffold for Blood Vessel Engineering. Biomaterials 2004, 25, 877– 886, DOI: 10.1016/s0142-9612(03)00593-3
  11
  Aligned biodegradable nanofibrous structure: a potential scaffold for blood vessel engineering
  Xu C Y; Inai R; Kotaki M; Ramakrishna S
  Biomaterials (2004), 25 (5), 877-86 ISSN:0142-9612.
  A unique biodegradable nanofibrous structure, aligned poly(L-lactid-co-epsilon-caprolactone) [P(LLA-CL)] (75:25) copolymer nanofibrous scaffold was produced by electrospinning. The diameter of the generated fibers was around 500 nm with an aligned topography which mimics the circumferential orientation of cells and fibrils found in the medial layer of a native artery. A favorable interaction between this scaffold with human coronary artery smooth muscle cells (SMCs) was demonstrated via MTS assay, phase contrast light microscopy, scanning electron microscopy, immunohistology assay and laser scanning confocal microscopy separately. Tissue culture polystyrene and plane solvent-cast P(LLA-CL) film were used as controls. The results showed that, the SMCs attached and migrated along the axis of the aligned nanofibers and expressed a spindle-like contractile phenotype; the distribution and organization of smooth muscle cytoskeleton proteins inside SMCs were parallel to the direction of the nanofibers; the adhesion and proliferation rate of SMCs on the aligned nanofibrous scaffold was significantly improved than on the plane polymer films. The above results strongly suggest that this synthetic aligned matrix combines with the advantages of synthetic biodegradable polymers, nanometer-scale dimension mimicking the natural ECM and a defined architecture replicating the in vivo-like vascular structure, may represent an ideal tissue engineering scaffold, especially for blood vessel engineering.
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12. 12
  Ju, Y. M.; Choi, J. S.; Atala, A.; Yoo, J. J.; Lee, S. J. Bilayered Scaffold for Engineering Cellularized Blood Vessels. Biomaterials 2010, 31, 4313– 4321, DOI: 10.1016/j.biomaterials.2010.02.002
  12
  Bilayered scaffold for engineering cellularized blood vessels
  Ju, Young Min; Choi, Jin San; Atala, Anthony; Yoo, James J.; Lee, Sang Jin
  Biomaterials (2010), 31 (15), 4313-4321CODEN: BIMADU; ISSN:0142-9612. (Elsevier Ltd.)
  Vascular scaffolds fabricated by electrospinning poly(ε-caprolactone) (PCL) and collagen were designed to provide adequate structural support as well as a favorable adhesion substrate for vascular cells. However, the presence of small-sized pores limits the efficacy of smooth muscle cells (SMC) seeding, as these cells could not adequately infiltrate into the scaffolds. To overcome this challenge, the authors developed a bilayered scaffolding system that provides different pore sizes to facilitate adequate cellular interactions. Based on the fact that pore size increases with the increase in fiber diam., 4 different fiber diams. (ranging 0.27-4.45 μm) were fabricated by electrospinning with controlled parameters. The fabricated scaffolds were examd. by evaluating cellular interactions, and the mech. properties were measured. Endothelial cells (EC) seeded on nanoscaled fibers showed enhanced cellular orientation and focal adhesion. Conversely, fabrication of a larger fiber diam. improved SMC infiltration into the scaffolds. To incorporate both of these properties into a scaffold, bilayered vascular scaffolds were produced. The inner layer yielded small diam. fibers and the outer layer provided large diam. fibers. The authors show that the bilayered scaffolds permit EC adhesion on the lumen and SMC infiltration into the outer layer. This study suggests that the use of bilayered scaffolds may lead to improved vessel formation.
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13. 13
  Ghasemi-Mobarakeh, L.; Prabhakaran, M. P.; Morshed, M.; Nasr-Esfahani, M.-H.; Ramakrishna, S. Electrospun Poly(ε-Caprolactone)/gelatin Nanofibrous Scaffolds for Nerve Tissue Engineering. Biomaterials 2008, 29, 4532– 4539, DOI: 10.1016/j.biomaterials.2008.08.007
  13
  Electrospun poly(ε-caprolactone)/gelatin nanofibrous scaffolds for nerve tissue engineering
  Ghasemi-Mobarakeh, Laleh; Prabhakaran, Molamma P.; Morshed, Mohammad; Nasr-Esfahani, Mohammad-Hossein; Ramakrishna, Seeram
  Biomaterials (2008), 29 (34), 4532-4539CODEN: BIMADU; ISSN:0142-9612. (Elsevier Ltd.)
  Nerve tissue engineering is one of the most promising methods to restore nerve systems in human health care. Scaffold design has pivotal role in nerve tissue engineering. Polymer blending is one of the most effective methods for providing new, desirable biocomposites for tissue-engineering applications. Random and aligned PCL/gelatin biocomposite scaffolds were fabricated by varying the ratios of PCL and gelatin concns. Chem. and mech. properties of PCL/gelatin nanofibrous scaffolds were measured by FTIR, porometry, contact angle and tensile measurements, while the in vitro biodegradability of the different nanofibrous scaffolds were evaluated too. PCL/gelatin 70:30 nanofiber was found to exhibit the most balanced properties to meet all the required specifications for nerve tissue and was used for in vitro culture of nerve stem cells (C17.2 cells). MTS assay and SEM results showed that the biocomposite of PCL/gelatin 70:30 nanofibrous scaffolds enhanced the nerve differentiation and proliferation compared to PCL nanofibrous scaffolds and acted as a pos. cue to support neurite outgrowth. It was found that the direction of nerve cell elongation and neurite outgrowth on aligned nanofibrous scaffolds is parallel to the direction of fibers. PCL/gelatin 70:30 nanofibrous scaffolds proved to be a promising biomaterial suitable for nerve regeneration.
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14. 14
  Yang, F.; Murugan, R.; Ramakrishna, S.; Wang, X.; Ma, Y.-X.; Wang, S. Fabrication of Nano-Structured Porous PLLA Scaffold Intended for Nerve Tissue Engineering. Biomaterials 2004, 25, 1891– 1900, DOI: 10.1016/j.biomaterials.2003.08.062
  14
  Fabrication of nano-structured porous PLLA scaffold intended for nerve tissue engineering
  Yang, F.; Murugan, R.; Ramakrishna, S.; Wang, X.; Ma, Y.-X.; Wang, S.
  Biomaterials (2004), 25 (10), 1891-1900CODEN: BIMADU; ISSN:0142-9612. (Elsevier Science Ltd.)
  Nerve tissue engineering (NTE) is one of the most promising methods to restore central nerve systems in human health care. Three-dimensional distribution and growth of cells within the porous scaffold are of clin. significance for NTE. In this study, an attempt was made to develop porous polymeric nano-fibrous scaffold using a biodegradable poly(L-lactic acid) (PLLA) for in vitro culture of nerve stem cells (NSCs). The processing of PLLA scaffold has been carried out by liq.-liq. phase sepn. method. The physico-chem. properties of the scaffold were fully characterized by using differential scanning calorimetry and SEM. These results confirmed that the prepd. scaffold is highly porous and fibrous with diams. down to nanometer scale. As our nano-structured PLLA scaffold mimics natural extracellular matrix, we have intended this biodegradable scaffold as cell carrier in NTE. The in vitro performance of NSCs seeded on nano-fibrous scaffold is addressed in this study. The cell cultural tests showed that the NSCs could differentiate on the nano-structured scaffold and the scaffold acted as a pos. cue to support neurite outgrowth. These results suggested that the nano-structured porous PLLA scaffold is a potential cell carrier in NTE.
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15. 15
  Zhong, Y.; Bellamkonda, R. V. Biomaterials for the Central Nervous System. J. R. Soc., Interface 2008, 5, 957– 975, DOI: 10.1098/rsif.2008.0071
  15
  Biomaterials for the central nervous system
  Zhong, Yinghui; Bellamkonda, Ravi V.
  Journal of the Royal Society, Interface (2008), 5 (26), 957-975CODEN: JRSICU; ISSN:1742-5689. (Royal Society)
  A review. Biomaterials are widely used to help treat neurol. disorders and/or improve functional recovery in the central nervous system (CNS). This article reviews the application of biomaterials in (i) shunting systems for hydrocephalus, (ii) cortical neural prosthetics, (iii) drug delivery in the CNS, (iv) hydrogel scaffolds for CNS repair, and (v) neural stem cell encapsulation for neurotrauma. The biol. and material requirements for the biomaterials in these applications are discussed. The difficulties that the biomaterials might face in each application and the possible solns. are also reviewed in this article.
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16. 16
  Oliveira, Á.; Corrêa-Velloso, J. d. C.; Glaser, T.; Ulrich, H. Stem Cells: Principles and Applications. Working with Stem Cells; Springer, 2016; pp 1– 14.
  There is no corresponding record for this reference.
17. 17
  Smith, A. G.; Heath, J. K.; Donaldson, D. D.; Wong, G. G.; Moreau, J.; Stahl, M.; Rogers, D. Inhibition of Pluripotential Embryonic Stem Cell Differentiation by Purified Polypeptides. Nature 1988, 336, 688– 690, DOI: 10.1038/336688a0
  There is no corresponding record for this reference.
18. 18
  Evans, M. J.; Kaufman, M. H. Establishment in Culture of Pluripotential Cells from Mouse Embryos. Nature 1981, 292, 154– 156, DOI: 10.1038/292154a0
  18
  Establishment in culture of pluripotential cells from mouse embryos
  Evans M J; Kaufman M H
  Nature (1981), 292 (5819), 154-6 ISSN:0028-0836.
  There is no expanded citation for this reference.
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19. 19
  Kurosawa, H. Methods for Inducing Embryoid Body Formation: In Vitro Differentiation System of Embryonic Stem Cells. J. Biosci. Bioeng. 2007, 103, 389– 398, DOI: 10.1263/jbb.103.389
  19
  Methods for inducing embryoid body formation: in vitro differentiation system of embryonic stem cells
  Kurosawa, Hiroshi
  Journal of Bioscience and Bioengineering (2007), 103 (5), 389-398CODEN: JBBIF6; ISSN:1389-1723. (Society for Biotechnology, Japan)
  When cultured in suspension without antidifferentiation factors, embryonic stem (ES) cells spontaneously differentiate and form three-dimensional multicellular aggregates called embryoid bodies (EBs). EBs recapitulate many aspects of cell differentiation during early embryogenesis, and play an important role in the differentiation of ES cells into a variety of cell types in vitro. There are several methods for inducing the formation of EBs from ES cells. The three basic methods are liq. suspension culture in bacterial-grade dishes, culture in methylcellulose semisolid media, and culture in hanging drops. Recently, the methods using a round-bottomed 96-well plate and a conical tube are adopted for forming EBs from predetd. nos. of ES cells. For the prodn. of large nos. of EBs, stirred-suspension culture using spinner flasks and bioreactors is performed. Each of these methods has its own peculiarity; thus, the features of formed EBs depending on the method used. Therefore, we should choose an appropriate method for EB formation according to the objective to be attained. In this review, we summarize the studies on in vitro differentiation of ES cells via EB formation and highlight the EB formation methods recently developed including the techniques, devices, and procedures involved.
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20. 20
  Tabar, V.; Studer, L. Pluripotent Stem Cells in Regenerative Medicine: Challenges and Recent Progress. Nat. Rev. Genet. 2014, 15, 82– 92, DOI: 10.1038/nrg3563
  20
  Pluripotent stem cells in regenerative medicine: challenges and recent progress
  Tabar, Viviane; Studer, Lorenz
  Nature Reviews Genetics (2014), 15 (2), 82-92CODEN: NRGAAM; ISSN:1471-0056. (Nature Publishing Group)
  A review. After years of incremental progress, several recent studies have succeeded in deriving disease-relevant cell types from human pluripotent stem cell (hPSC) sources. The prospect of an unlimited cell source, combined with promising preclin. data, indicates that hPSC technol. may be on the verge of clin. translation. In this Review, we discuss recent progress in directed differentiation, some of the new technologies that have facilitated the success of hPSC therapies and the remaining hurdles on the road towards developing hPSC-based cell therapies.
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21. 21
  Trounson, A.; Dewitt, N. D. Pluripotent Stem Cells Progressing to the Clinic. Nat. Rev. Mol. Cell Biol. 2016, 17, 194– 200, DOI: 10.1038/nrm.2016.10
  21
  Pluripotent stem cells progressing to the clinic
  Trounson, Alan; DeWitt, Natalie D.
  Nature Reviews Molecular Cell Biology (2016), 17 (3), 194-200CODEN: NRMCBP; ISSN:1471-0072. (Nature Publishing Group)
  Basic exptl. stem cell research has opened up the possibility of many diverse clin. applications; however, translation to clin. trials has been restricted to only a few diseases. To broaden this clin. scope, pluripotent stem cell derivs. provide a uniquely scalable source of functional differentiated cells that can potentially repair damaged or diseased tissues to treat a wide spectrum of diseases and injuries. However, gathering sound data on their distribution, longevity, function and mechanisms of action in host tissues is imperative to realizing their clin. benefit. The large-scale availability of treatments involving pluripotent stem cells remains some years away, because of the long and demanding regulatory pathway that is needed to ensure their safety.
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22. 22
  Mahla, R. S. Stem Cells Applications in Regenerative Medicine and Disease Therapeutics. Int. J. Cell Biol. 2016, 2016, 6940283, DOI: 10.1155/2016/6940283
  22
  Stem Cells Applications in Regenerative Medicine and Disease Therapeutics
  Mahla Ranjeet Singh
  International journal of cell biology (2016), 2016 (), 6940283 ISSN:1687-8876.
  Regenerative medicine, the most recent and emerging branch of medical science, deals with functional restoration of tissues or organs for the patient suffering from severe injuries or chronic disease. The spectacular progress in the field of stem cell research has laid the foundation for cell based therapies of disease which cannot be cured by conventional medicines. The indefinite self-renewal and potential to differentiate into other types of cells represent stem cells as frontiers of regenerative medicine. The transdifferentiating potential of stem cells varies with source and according to that regenerative applications also change. Advancements in gene editing and tissue engineering technology have endorsed the ex vivo remodelling of stem cells grown into 3D organoids and tissue structures for personalized applications. This review outlines the most recent advancement in transplantation and tissue engineering technologies of ESCs, TSPSCs, MSCs, UCSCs, BMSCs, and iPSCs in regenerative medicine. Additionally, this review also discusses stem cells regenerative application in wildlife conservation.
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23. 23
  Segers, V. F. M.; Lee, R. T. Stem-Cell Therapy for Cardiac Disease. Nature 2008, 451, 937– 942, DOI: 10.1038/nature06800
  23
  Stem-cell therapy for cardiac disease
  Segers, Vincent F. M.; Lee, Richard T.
  Nature (London, United Kingdom) (2008), 451 (7181), 937-942CODEN: NATUAS; ISSN:0028-0836. (Nature Publishing Group)
  A review. Heart failure is the leading cause of death worldwide, and current therapies only delay progression of the disease. Lab. expts. and recent clin. trials suggest that cell-based therapies can improve cardiac function, and the implications of this for cardiac regeneration are causing great excitement. Bone-marrow-derived progenitor cells and other progenitor cells can differentiate into vascular cell types, restoring blood flow. More recently, resident cardiac stem cells have been shown to differentiate into multiple cell types present in the heart, including cardiac muscle cells, indicating that the heart is not terminally differentiated. These new findings have stimulated optimism that the progression of heart failure can be prevented or even reversed with cell-based therapy.
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24. 24
  Lindvall, O.; Kokaia, Z. Stem Cells for the Treatment of Neurological Disorders. Nature 2006, 441, 1094, DOI: 10.1038/nature04960
  24
  Stem cells for the treatment of neurological disorders
  Lindvall, Olle; Kokaia, Zaal
  Nature (London, United Kingdom) (2006), 441 (7097), 1094-1096CODEN: NATUAS; ISSN:0028-0836. (Nature Publishing Group)
  A review. Many common neurol. disorders, such as Parkinson's disease, stroke and multiple sclerosis, are caused by a loss of neurons and glial cells. In recent years, neurons and glia have been generated successfully from stem cells in culture, fueling efforts to develop stem-cell-based transplantation therapies for human patients. More recently, efforts have been extended to stimulating the formation and preventing the death of neurons and glial cells produced by endogenous stem cells within the adult central nervous system. The next step is to translate these exciting advances from the lab. into clin. useful therapies.
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25. 25
  Murphy, W. L.; McDevitt, T. C.; Engler, A. J. Materials as Stem Cell Regulators. Nat. Mater. 2014, 13, 547– 557, DOI: 10.1038/nmat3937
  25
  Materials as stem cell regulators
  Murphy, William L.; McDevitt, Todd C.; Engler, Adam J.
  Nature Materials (2014), 13 (6), 547-557CODEN: NMAACR; ISSN:1476-1122. (Nature Publishing Group)
  A review. The stem cell/material interface is a complex, dynamic microenvironment in which the cell and the material cooperatively dictate one another's fate: the cell by remodelling its surroundings, and the material through its inherent properties (such as adhesivity, stiffness, nanostructure or degradability). Stem cells in contact with materials are able to sense their properties, integrate cues via signal propagation and ultimately translate parallel signalling information into cell fate decisions. However, discovering the mechanisms by which stem cells respond to inherent material characteristics is challenging because of the highly complex, multicomponent signalling milieu present in the stem cell environment. In this Review, we discuss recent evidence that shows that inherent material properties may be engineered to dictate stem cell fate decisions, and overview a subset of the operative signal transduction mechanisms that have begun to emerge. Further developments in stem cell engineering and mechanotransduction are poised to have substantial implications for stem cell biol. and regenerative medicine.
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26. 26
  Semeano, A. T.; Glaser, T.; Ulrich, H. Scaffolds for Embryonic Stem Cell Growth and Differentiation. Working with Stem Cells; Springer, 2016; pp 347– 365.
  There is no corresponding record for this reference.
27. 27
  Krishna, L.; Dhamodaran, K.; Jayadev, C.; Chatterjee, K.; Shetty, R.; Khora, S. S. Nanostructured Scaffold as a Determinant of Stem Cell Fate. Stem Cell Res. Ther. 2016, 7, 188, DOI: 10.1186/s13287-016-0440-y
  27
  Nanostructured scaffold as a determinant of stem cell fate
  Krishna, Lekshmi; Dhamodaran, Kamesh; Jayadev, Chaitra; Chatterjee, Kaushik; Shetty, Rohit; Khora, S. S.; Das, Debashish
  Stem Cell Research & Therapy (2016), 7 (), 188/1-188/12CODEN: SCRTEK; ISSN:1757-6512. (BioMed Central Ltd.)
  A review. The functionality of stem cells is tightly regulated by cues from the niche, comprising both intrinsic and extrinsic cell signals. Besides chem. and growth factors, biophys. signals are important components of extrinsic signals that dictate the stem cell properties. The materials used in the fabrication of scaffolds provide the chem. cues whereas the shape of the scaffolds provides the biophys. cues. The effect of the chem. compn. of the scaffolds on stem cell fate is well researched. Biophys. signals such as nanotopog., mech. forces, stiffness of the matrix, and roughness of the biomaterial influence the fate of stem cells. However, not much is known about their role in signaling crosstalk, stem cell maintenance, and directed differentiation. Among the various techniques for scaffold design, nanotechnol. has special significance. The role of nanoscale topog. in scaffold design for the regulation of stem cell behavior has gained importance in regenerative medicine. Nanotechnol. allows manipulation of highly advanced surfaces/scaffolds for optimal regulation of cellular behavior. Techniques such as electrospinning, soft lithog., microfluidics, carbon nanotubes, and nanostructured hydrogel are described in this review, along with their potential usage in regenerative medicine. We have also provided a brief insight into the potential signaling crosstalk that is triggered by nanomaterials that dictate a specific outcome of stem cells. This concise review compiles recent developments in nanoscale architecture and its importance in directing stem cell differentiation for prospective therapeutic applications.
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28. 28
  Vert, M.; Li, S. M.; Spenlehauer, G.; Guerin, P. Bioresorbability and Biocompatibility of Aliphatic Polyesters. J. Mater. Sci.: Mater. Med. 1992, 3, 432– 446, DOI: 10.1007/bf00701240
  28
  Bioresorbability and biocompatibility of aliphatic polyesters
  Vert, M.; Li, S. M.; Spenlehauer, G.; Guerin, P.
  Journal of Materials Science: Materials in Medicine (1992), 3 (6), 432-46CODEN: JSMMEL; ISSN:0957-4530.
  A review with 103 refs. on the complex phenomena of biodegradability and biocompatibility of polyesters, esp. poly(α-hydroxy acids), for temporary surgical and pharmacol. applications. The degrdn. of a polymer leads to the delivery of low mol. wt. degrdn. byproducts whose effects on the host body have to be considered. The consequences of the absence of std. terminol. are first discussed with respect to words such as biodegradable and bioresorbable. Poly(α-hydroxy acids) derived from lactic and glycolic acids are discussed, as well as biocompatibility, biodegradability, bioresorbability, mechanism of hydrolysis (enzymic vs. simple chem.), polymodality of mol. wt. distributions during degrdn. and the effects of the presence of oligomers. Finally, some specific comments are made on other aliph. polyesters such as poly(hydroxy butyrate) and poly(β-malic acid).
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29. 29
  Hutmacher, D. W. Scaffolds in Tissue Engineering Bone and Cartilage. Biomaterials 2000, 21, 2529– 2543, DOI: 10.1016/s0142-9612(00)00121-6
  29
  Scaffolds in tissue engineering bone and cartilage
  Hutmacher, D. W.
  Biomaterials (2000), 21 (24), 2529-2543CODEN: BIMADU; ISSN:0142-9612. (Elsevier Science Ltd.)
  A review with 82 refs. Musculoskeletal tissue, bone and cartilage are under extensive investigation in tissue engineering research. A no. of biodegradable and bioresorbable materials, as well as scaffold designs, have been exptl. and/or clin. studied. Ideally, a scaffold should have the following characteristics: (i) 3-dimensional and highly porous with an interconnected pore network for cell growth and flow transport of nutrients and metabolic waste; (ii) biocompatible and bioresorbable with a controllable degrdn. and resorption rate to match cell/tissue growth in vitro and/or in vivo; (iii) suitable surface chem. for cell attachment, proliferation, and differentiation and (iv) mech. properties to match those of the tissues at the site of implantation. This paper reviews research on the tissue engineering of bone and cartilage from the polymeric scaffold point of view.
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30. 30
  Nair, L. S.; Laurencin, C. T. Biodegradable Polymers as Biomaterials. Prog. Polym. Sci. 2007, 32, 762– 798, DOI: 10.1016/j.progpolymsci.2007.05.017
  30
  Biodegradable polymers as biomaterials
  Nair, Lakshmi S.; Laurencin, Cato T.
  Progress in Polymer Science (2007), 32 (8-9), 762-798CODEN: PRPSB8; ISSN:0079-6700. (Elsevier Ltd.)
  A review. During the past 2 decades significant advances were made in the development of biodegradable polymeric materials for biomedical applications. Degradable polymeric biomaterials are preferred candidates for developing therapeutic devices such as temporary prostheses, 3-dimensional porous structures as scaffolds for tissue engineering and as controlled/sustained release drug delivery vehicles. Each of these applications demands materials with specific phys., chem., biol., biomech. and degrdn. properties to provide efficient therapy. Consequently, a wide range of natural or synthetic polymers capable of undergoing degrdn. by hydrolytic or enzymic route are being investigated for biomedical applications. This review summarizes the main advances published over the last 15 years, outlining the synthesis, biodegradability and biomedical applications of biodegradable synthetic and natural polymers.
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31. 31
  Mooney, D. Stabilized Polyglycolic Acid Fibre-Based Tubes for Tissue Engineering. Biomaterials 1996, 17, 115– 124, DOI: 10.1016/0142-9612(96)85756-5
  31
  Stabilized polyglycolic acid fiber-based tubes for tissue engineering
  Mooney, D. J.; Mazzoni, C. L.; Breuer, C.; McNamara, K.; Hern, D.; Vacanti, J. P.; Langer, R.
  Biomaterials (1996), 17 (2), 115-24CODEN: BIMADU; ISSN:0142-9612. (Elsevier)
  Polyglycolic acid (PGA) fiber meshes are attractive candidates to transplant cells, but they are incapable of resisting significant compressional forces. To stabilize PGA meshes, atomized solns. of poly(L-lactic acid) (PLLA) and a 50/50 copolymer of poly(D,L-lactic-co-glycolic acid) (PLGA) dissolved in chloroform were sprayed over meshes formed into hollow tubes. The PLLA and PLGA coated the PGA fibers and phys. bonded adjacent fibers. The pattern and extent of bonding was controlled by the concn. of polymer in the atomized soln. and the total mass of polymer sprayed on the device. The compression resistance of devices increased with the extent of bonding, and PLLA bonded tubes resisted larger compressive forces than PLGA bonded tubes. Tubes bonded with PLLA degraded more slowly than devices bonded with PLGA. Implantation of PLLA bonded tubes into rats revealed that the devices maintained their structure during fibrovascular tissue ingrowth, resulting in the formation of a tubular structure with a central lumen. The potential of these devices to engineer specific tissues was exhibited by the finding that smooth muscle cells and endothelial cells seeded onto devices in vitro formed a tubular tissue with appropriate cell distribution.
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32. 32
  Moutos, F. T.; Freed, L. E.; Guilak, F. A Biomimetic Three-Dimensional Woven Composite Scaffold for Functional Tissue Engineering of Cartilage. Nat. Mater. 2007, 6, 162– 167, DOI: 10.1038/nmat1822
  32
  A biomimetic three-dimensional woven composite scaffold for functional tissue engineering of cartilage
  Moutos, Franklin T.; Freed, Lisa E.; Guilak, Farshid
  Nature Materials (2007), 6 (2), 162-167CODEN: NMAACR; ISSN:1476-1122. (Nature Publishing Group)
  Tissue engineering seeks to repair or regenerate tissues through combinations of implanted cells, biomaterial scaffolds and biol. active mols. The rapid restoration of tissue biomech. function remains an important challenge, emphasizing the need to replicate structural and mech. properties using novel scaffold designs. Here we present a microscale 3D weaving technique to generate anisotropic 3D woven structures as the basis for novel composite scaffolds that are consolidated with a chondrocyte-hydrogel mixt. into cartilage tissue constructs. Composite scaffolds show mech. properties of the same order of magnitude as values for native articular cartilage, as measured by compressive, tensile and shear testing. Moreover, our findings showed that porous composite scaffolds could be engineered with initial properties that reproduce the anisotropy, viscoelasticity and tension-compression nonlinearity of native articular cartilage. Such scaffolds uniquely combine the potential for load-bearing immediately after implantation in vivo with biol. support for cell-based tissue regeneration without requiring cultivation in vitro.
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33. 33
  Verrier, S.; Blaker, J. J.; Maquet, V.; Hench, L. L.; Boccaccini, A. R. PDLLA/Bioglass Composites for Soft-Tissue and Hard-Tissue Engineering: An in Vitro Cell Biology Assessment. Biomaterials 2004, 25, 3013– 3021, DOI: 10.1016/j.biomaterials.2003.09.081
  33
  PDLLA/Bioglass composites for soft-tissue and hard-tissue engineering: an in vitro cell biology assessment
  Verrier, Sophie; Blaker, Jonny J.; Maquet, Veronique; Hench, Larry L.; Boccaccini, Aldo R.
  Biomaterials (2004), 25 (15), 3013-3021CODEN: BIMADU; ISSN:0142-9612. (Elsevier Science Ltd.)
  The aim of this study was to examine the effect of increased content of 45S5 Bioglass (0-40%) in poly(dl-lactic acid) (PDLLA) porous foams on the behavior of MG-63 (human osteosarcoma cell line) and A549 cells (human lung carcinoma cell line). The ability of these cell lines to grow on bioactive composites was quant. investigated in order to assess the potentiality for their use in hard and soft-tissue engineering. Two hours after cell seeding, an increase of cell adhesion according to the increased content of Bioglass present in the foams for both cell types was obsd. Cell proliferation studies performed over a period of 4 wk showed a better aptitude of the A549 cells to proliferate on PDLLA foams contg. 5% Bioglass when compared to the proliferation on foams with 40% Bioglass. A lower proliferation rate was obtained for cells on pure PDLLA. SEM anal. showed for both cell types the presence of cells inside the porous structure of the foams. These results confirmed the biocompatibility of PDLLA/Bioglass composite foams and the pos. effect of Bioglass on MG-63 cell behavior and also showed for the first time the possibility for human lung epithelial type II cells to adhere and proliferate on these porous scaffolds. In addn., we describe a pos. effect of 45S5 Bioglass on A549 cell behavior in a dose-dependent manner, indicating the potential of using PDLLA/Bioglass composites with an optimal concn. of 45S5 Bioglass not only in bone tissue engineering but also in lung tissue engineering.
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34. 34
  Yang, F.; Xu, C. Y.; Kotaki, M.; Wang, S.; Ramakrishna, S. Characterization of Neural Stem Cells on Electrospun poly(L-Lactic Acid) Nanofibrous Scaffold. J. Biomater. Sci., Polym. Ed. 2004, 15, 1483– 1497, DOI: 10.1163/1568562042459733
  34
  Characterization of neural stem cells on electrospun poly(L-lactic acid) nanofibrous scaffold
  Yang, F.; Xu, C. Y.; Kotaki, M.; Wang, S.; Ramakrishna, S.
  Journal of Biomaterials Science, Polymer Edition (2004), 15 (12), 1483-1497CODEN: JBSEEA; ISSN:0920-5063. (VSP)
  Nanofibrous poly(L-lactic acid) (PLLA) scaffolds were fabricated by an electrospinning technique and characterized by SEM, mercury porosimeter, at. force microscopy and contact-angle test. The produced PLLA fibers with diams. ranging from 150 to 350 nm were randomly oriented with interconnected pores varying from several μm to about 140 μm in-between to form a three-dimensional architecture, which resembles the natural extracellular matrix structure in human body. The in vitro cell culture study was performed and the results indicate that the nanofibrous scaffold not only supports neural stem cell (NSC) differentiation and neurites out-growth, but also promotes NSC adhesion. The favorable interaction between the NSCs and the nanofibrous scaffold may be due to the greatly improved surface roughness of the electrospun nanofibrous scaffold. As evidenced by this study, the electrospun nanofibrous scaffold is expected to play a significant role in neural tissue engineering.
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35. 35
  Yang, F.; Murugan, R.; Wang, S.; Ramakrishna, S. Electrospinning of Nano/micro Scale Poly(l-Lactic Acid) Aligned Fibers and Their Potential in Neural Tissue Engineering. Biomaterials 2005, 26, 2603– 2610, DOI: 10.1016/j.biomaterials.2004.06.051
  35
  Electrospinning of nano/micro scale poly(L-lactic acid) aligned fibers and their potential in neural tissue engineering
  Yang, F.; Murugan, R.; Wang, S.; Ramakrishna, S.
  Biomaterials (2005), 26 (15), 2603-2610CODEN: BIMADU; ISSN:0142-9612. (Elsevier Ltd.)
  Efficacy of aligned poly(-lactic acid) (PLLA) nano/micro fibrous scaffolds for neural tissue engineering is described and their performance with random PLLA scaffolds is compared as well in this study. Perfectly aligned PLLA fibrous scaffolds were fabricated by an electrospinning technique under optimum condition and the diam. of the electrospun fibers can easily be tailored by adjusting the concn. of polymer soln. As the structure of PLLA scaffold was intended for neural tissue engineering, its suitability was evaluated in vitro using neural stem cells (NSCs) as a model cell line. Cell morphol., differentiation and neurite outgrowth were studied by various microscopic techniques. The results show that the direction of NSC elongation and its neurite outgrowth is parallel to the direction of PLLA fibers for aligned scaffolds. No significant changes were obsd. on the cell orientation with respect to the fiber diams. However, the rate of NSC differentiation was higher for PLLA nanofibers than that of micro fibers and it was independent of the fiber alignment. Based on the exptl. results, the aligned nanofibrous PLLA scaffold could be used as a potential cell carrier in neural tissue engineering.
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36. 36
  Kweon, H. A Novel Degradable Polycaprolactone Networks for Tissue Engineering. Biomaterials 2003, 24, 801– 808, DOI: 10.1016/s0142-9612(02)00370-8
  36
  A novel degradable polycaprolactone networks for tissue engineering
  Kweon, HaeYong; Yoo, Mi Kyong; Park, In Kyu; Kim, Tae Hee; Lee, Hyun Chul; Lee, Hyun-Sook; Oh, Jong-Suk; Akaike, Toshihiro; Cho, Chong-Su
  Biomaterials (2003), 24 (5), 801-808CODEN: BIMADU; ISSN:0142-9612. (Elsevier Science Ltd.)
  Polycaprolactone (PCL) macromer was obtained by the reaction of PCL diol with acryloyl chloride and confirmed using Fourier transform IR and NMR spectrometer. Novel degradable PCL networks were prepd. through photopolymn. of the PCL macromer. Thermal, mech., and morphol. characteristics as well as degradability and biocompatibility of the PCL networks were investigated. DSC showed that the melting temp. and the calcd. wt. av. crystallinity of PCL networks were decreased with a decrease of mol. wt. of PCL diols due to the increased crosslinking d. Thermal stability of PCL networks was higher than that of PCL diols. PCL networks showed faster degrdn., and higher compressive modulus and compressive recovery ratios than those of PCL itself because of their low crystallinity and the modification of terminal groups. The porosity of the PCL networks can be controlled by the amts. and size of porogen used. MG-63 osteoblast cell was attached and proliferated on PCL networks. PCL networks therefore may have considerable potential as scaffold for tissue engineering.
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37. 37
  Yang, S.; Leong, K.-F.; Du, Z.; Chua, C.-K. The Design of Scaffolds for Use in Tissue Engineering. Part I. Traditional Factors. Tissue Eng. 2001, 7, 679– 689, DOI: 10.1089/107632701753337645
  37
  The design of scaffolds for use in tissue engineering. Part I. Traditional factors
  Yang S; Leong K F; Du Z; Chua C K
  Tissue engineering (2001), 7 (6), 679-89 ISSN:1076-3279.
  In tissue engineering, a highly porous artificial extracellular matrix or scaffold is required to accommodate mammalian cells and guide their growth and tissue regeneration in three dimensions. However, existing three-dimensional scaffolds for tissue engineering proved less than ideal for actual applications, not only because they lack mechanical strength, but they also do not guarantee interconnected channels. In this paper, the authors analyze the factors necessary to enhance the design and manufacture of scaffolds for use in tissue engineering in terms of materials, structure, and mechanical properties and review the traditional scaffold fabrication methods. Advantages and limitations of these traditional methods are also discussed.
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38. 38
  Chen, C.-C.; Chueh, J.-Y.; Tseng, H.; Huang, H.-M.; Lee, S.-Y. Preparation and Characterization of Biodegradable PLA Polymeric Blends. Biomaterials 2003, 24, 1167– 1173, DOI: 10.1016/s0142-9612(02)00466-0
  38
  Preparation and characterization of biodegradable PLA polymeric blends
  Chen, Chien-Chung; Chueh, Ju-Yu; Tseng, How; Huang, Haw-Ming; Lee, Sheng-Yang
  Biomaterials (2003), 24 (7), 1167-1173CODEN: BIMADU; ISSN:0142-9612. (Elsevier Science Ltd.)
  The purpose of this study was to fine-tune the mech. properties of high mol.-wt. poly-l-lactic acid (PLLA), esp. to increase its toughness without sacrificing too much of its original strength. Besides of its long degrdn. time, PLLA is usually hard and brittle, which hinders its usage in medical applications, i.e., orthopedic and dental surgery. Some modifications, such as the addn. of plasticizers or surfactants/compatibilizers, are usually required to improve its original properties. PDLLA can degrade quickly due to its amorphous structure, thus shortening the degrdn. time of PLLA/PDLLA blends. Blends of biodegradable poly-l-lactic acid (PLLA) and poly-dl-lactic acid (PDLLA) or polycaprolactone (PCL), in addn. to a third component, the surfactant-a copolymer of ethylene oxide and propylene oxide, were prepd. by blending these three polymers at various ratios using dichloromethane as a solvent. The wt. percentages of PLLA/PDLLA (or PCL) blends were 100%/0%, 80%/20%, 60%/40%, 50%/50%, 40%/60%, 20%/80% and 0%/100%, resp. Phys. properties such as the cryst. m.p., glass transition point (Tg), phase behavior, degrdn. behavior, and other mech. properties were characterized by thermogravimetric anal., DSC, IR spectroscopy, gel permeation chromatog., and dynamic mech. anal. (DMA). DSC data indicate that PLLA/PDLLA blends without the surfactant had two Tg's. With the addn. of the surfactant, there was a linear shift of the single Tg as a function of compn., with lower percentages of PLLA producing lower glass transition temps. indicating that better miscibility had been achieved. DMA data show that the 40/60 PLLA/PDLLA blends without the surfactant had high elastic modulus and elongation, and similar results were obsd. after adding 2% surfactant into the blends. The 50/50 PLLA/PDLLA/2% surfactant blend had the highest elastic modulus, yield strength, and break strength compared with other ratios of PLLA/PDLLA/2% surfactant blends. The elongation at break of 50/50 PLLA/PDLLA was similar to that of PLLA. Again, the elongation at break of 50/50 PLLA/PDLLA/2% surfactant was almost 1.2-1.9 times higher than that of 50/50 PLLA/PDLLA and PLLA. Elongation of PLLA increased with the addn. of PCL, but the strength decreased at the same time. In conclusions, adding PDLLA and surfactant to PLLA via soln.-blending may be an effective way to make PLLA tougher and more suitable to use in orthopedic or dental applications.
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39. 39
  Ulery, B. D.; Nair, L. S.; Laurencin, C. T. Biomedical Applications of Biodegradable Polymers. J. Polym. Sci., Part B: Polym. Phys. 2011, 49, 832– 864, DOI: 10.1002/polb.22259
  39
  Biomedical applications of biodegradable polymers
  Ulery, Bret D.; Nair, Lakshmi S.; Laurencin, Cato T.
  Journal of Polymer Science, Part B: Polymer Physics (2011), 49 (12), 832-864CODEN: JPBPEM; ISSN:0887-6266. (John Wiley & Sons, Inc.)
  A review. Utilization of polymers as biomaterials has greatly impacted the advancement of modern medicine. Specifically, polymeric biomaterials that are biodegradable provide the significant advantage of being able to be broken down and removed after they have served their function. Applications are wide ranging with degradable polymers being used clin. as surgical sutures and implants. To fit functional demand, materials with desired phys., chem., biol., biomech., and degrdn. properties must be selected. Fortunately, a wide range of natural and synthetic degradable polymers has been investigated for biomedical applications with novel materials constantly being developed to meet new challenges. This review summarizes the most recent advances in the field over the past 4 years, specifically highlighting new and interesting discoveries in tissue engineering and drug delivery applications. © 2011 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2011.
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40. 40
  Chen, J.; Dong, R.; Ge, J.; Guo, B.; Ma, P. X. Biocompatible, Biodegradable, and Electroactive Polyurethane-Urea Elastomers with Tunable Hydrophilicity for Skeletal Muscle Tissue Engineering. ACS Appl. Mater. Interfaces 2015, 7, 28273– 28285, DOI: 10.1021/acsami.5b10829
  40
  Biocompatible, Biodegradable, and Electroactive Polyurethane-Urea Elastomers with Tunable Hydrophilicity for Skeletal Muscle Tissue Engineering
  Chen, Jing; Dong, Ruonan; Ge, Juan; Guo, Baolin; Ma, Peter X.
  ACS Applied Materials & Interfaces (2015), 7 (51), 28273-28285CODEN: AAMICK; ISSN:1944-8244. (American Chemical Society)
  It remains a challenge to develop electroactive and elastic biomaterials to mimic the elasticity of soft tissue and to regulate the cell behavior during tissue regeneration. We designed and synthesized a series of novel electroactive and biodegradable polyurethane-urea (PUU) copolymers with elastomeric property by combining the properties of polyurethanes and conducting polymers. The electroactive PUU copolymers were synthesized from amine capped aniline trimer (ACAT), dimethylol propionic acid (DMPA), polylactide, and hexamethylene diisocyanate. The electroactivity of the PUU copolymers were studied by UV-vis spectroscopy and cyclic voltammetry. Elasticity and Young's modulus were tailored by the polylactide segment length and ACAT content. Hydrophilicity of the copolymer films was tuned by changing DMPA content and doping of the copolymer. Cytotoxicity of the PUU copolymers was evaluated by mouse C2C12 myoblast cells. The myogenic differentiation of C2C12 myoblasts on copolymer films was also studied by analyzing the morphol. of myotubes and relative gene expression during myogenic differentiation. The chem. structure, thermal properties, surface morphol., and processability of the PUU copolymers were characterized by NMR, FT-IR, gel permeation chromatog. (GPC), thermogravimetric anal. (TGA), differential scanning calorimetry (DSC), x-ray diffraction (x-ray diffraction), SEM, at. force microscopy (AFM), and soly. testing, resp. Those biodegradable electroactive elastic PUU copolymers are promising materials for repair of soft tissues such as skeletal muscle, cardiac muscle, and nerve.
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41. 41
  Cui, H.; Liu, Y.; Deng, M.; Pang, X.; Zhang, P.; Wang, X.; Chen, X.; Wei, Y. Synthesis of Biodegradable and Electroactive Tetraaniline Grafted Poly(ester Amide) Copolymers for Bone Tissue Engineering. Biomacromolecules 2012, 13, 2881– 2889, DOI: 10.1021/bm300897j
  41
  Synthesis of Biodegradable and Electroactive Tetraaniline Grafted Poly(ester amide) Copolymers for Bone Tissue Engineering
  Cui, Haitao; Liu, Yadong; Deng, Mingxiao; Pang, Xuan; Zhang, Peibiao; Wang, Xianhong; Chen, Xuesi; Wei, Yen
  Biomacromolecules (2012), 13 (9), 2881-2889CODEN: BOMAF6; ISSN:1525-7797. (American Chemical Society)
  Biodegradable poly(ester amide)s have recently been used as biomaterials due to their desirable chem. and biol. characteristics as well as their mech. properties, which are amendable for material processing. In this study, electroactive tetraaniline (TA) grafted poly(ester amide)s were successfully synthesized and characterized. The poly(ester amide)s-graft-tetraaniline copolymers (PEA-g-TA) exhibited good electroactivity, mech. properties, and biodegradability. The biocompatibility of the PEA-g-TA copolymers in vitro was systematically studied, which demonstrated that they were nontoxic and led to favorable adhesion and proliferation of mouse preosteoblastic MC3T3-E1 cells. Moreover, the PEA-g-TA copolymers stimulated by pulsed elec. signal could serve to promote the differentiation of MC3T3-E1 cells compared with TCPs. Hence, the biodegradable and electroactive PEA-g-TA copolymers possessed the properties in favor of the long-time potential application in vivo (elec. stimulation directly to the desired area) as bone repair scaffold materials in tissue engineering.
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42. 42
  Balint, R.; Cassidy, N. J.; Cartmell, S. H. Conductive Polymers: Towards a Smart Biomaterial for Tissue Engineering. Acta Biomater. 2014, 10, 2341– 2353, DOI: 10.1016/j.actbio.2014.02.015
  42
  Conductive polymers: Towards a smart biomaterial for tissue engineering
  Balint, Richard; Cassidy, Nigel J.; Cartmell, Sarah H.
  Acta Biomaterialia (2014), 10 (6), 2341-2353CODEN: ABCICB; ISSN:1742-7061. (Elsevier Ltd.)
  A review. Developing stimulus-responsive biomaterials with easy-to-tailor properties is a highly desired goal of the tissue engineering community. A novel type of electroactive biomaterial, the conductive polymer, promises to become one such material. Conductive polymers are already used in fuel cells, computer displays and microsurgical tools, and are now finding applications in the field of biomaterials. These versatile polymers can be synthesized alone, as hydrogels, combined into composites or electrospun into microfibres. They can be created to be biocompatible and biodegradable. Their phys. properties can easily be optimized for a specific application through binding biol. important mols. into the polymer using one of the many available methods for their functionalization. Their conductive nature allows cells or tissue cultured upon them to be stimulated, the polymers' own phys. properties to be influenced post-synthesis and the drugs bound in them released, through the application of an elec. signal. It is thus little wonder that these polymers are becoming very important materials for biosensors, neural implants, drug delivery devices and tissue engineering scaffolds. Focusing mainly on polypyrrole, polyaniline and poly(3,4-ethylenedioxythiophene), we review conductive polymers from the perspective of tissue engineering. The basic properties of conductive polymers, their chem. and electrochem. synthesis, the phenomena underlying their cond. and the ways to tailor their properties (functionalization, composites, etc.) are discussed.
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43. 43
  Ateh, D. D.; Navsaria, H. A.; Vadgama, P. Polypyrrole-Based Conducting Polymers and Interactions with Biological Tissues. J. R. Soc., Interface 2006, 3, 741– 752, DOI: 10.1098/rsif.2006.0141
  43
  Polypyrrole-based conducting polymers and interactions with biological tissues
  Ateh, D. D.; Navsaria, H. A.; Vadgama, P.
  Journal of the Royal Society, Interface (2006), 3 (11), 741-752CODEN: JRSICU; ISSN:1742-5689. (Royal Society)
  A review. Polypyrrole (PPy) is a conjugated polymer that displays particular electronic properties including cond. In biomedical applications, it is usually electrochem. generated with the incorporation of any anionic species including also neg. charged biol. macromols. such as proteins and polysaccharides to give composite materials. In biomedical research, it has mainly been assessed for its role as a reporting interface in biosensors. However, there is an increasing literature on the application of PPy as a potentially elec. addressable tissue/cell support substrate. Here, we review studies that have considered such PPy based conducting polymers in direct contact with biol. tissues and conclude that due to its versatile functional properties, it could contribute to a new generation of biomaterials.
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44. 44
  Svennersten, K.; Bolin, M. H.; Jager, E. W. H.; Berggren, M.; Richter-Dahlfors, A. Electrochemical Modulation of Epithelia Formation Using Conducting Polymers. Biomaterials 2009, 30, 6257– 6264, DOI: 10.1016/j.biomaterials.2009.07.059
  44
  Electrochemical modulation of epithelia formation using conducting polymers
  Svennersten, Karl; Bolin, Maria H.; Jager, Edwin W. H.; Berggren, Magnus; Richter-Dahlfors, Agneta
  Biomaterials (2009), 30 (31), 6257-6264CODEN: BIMADU; ISSN:0142-9612. (Elsevier Ltd.)
  Conducting polymers are soft, flexible materials, exhibiting material properties that can be reversibly changed by electrochem. altering the redox state. Surface chem. is an important determinant for the mol. events of cell adhesion. Therefore, we analyzed whether the redox state of the conducting polymer PEDOT:Tosylate can be used to control epithelial cell adhesion and proliferation. A functionalized cell culture dish comprising two adjacent electrode surfaces was developed. Upon electronic addressing, reduced and oxidized surfaces are created within the same device. Simultaneous anal. of how a homogeneous epithelial MDCK cell population responded to the electrodes revealed distinct surface-specific differences. Presentation of functional fibronectin on the reduced electrode promoted focal adhesion formation, involving αvβ3 integrin, cell proliferation, and ensuing formation of polarized monolayers. In contrast, the oxidized surface harbored only few cells with deranged morphol. showing no indication of proliferation. This stems from the altered fibronectin conformation, induced by the different surface chem. of the PEDOT:Tosylate electrode in the oxidized state. Our results demonstrate a novel use of PEDOT:Tosylate as a cell-hosting material in multiple-electrode systems, where cell adhesion and proliferation can be controlled by electrochem. modulation of surface properties.
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45. 45
  Bolin, M. H.; Svennersten, K.; Wang, X.; Chronakis, I. S.; Richter-Dahlfors, A.; Jager, E. W. H.; Berggren, M. Nano-Fiber Scaffold Electrodes Based on PEDOT for Cell Stimulation. Sens. Actuators, B 2009, 142, 451– 456, DOI: 10.1016/j.snb.2009.04.062
  45
  Nano-fiber scaffold electrodes based on PEDOT for cell stimulation
  Bolin, Maria H.; Svennersten, Karl; Wang, Xiangjun; Chronakis, Ioannis S.; Richter-Dahlfors, Agneta; Jager, Edwin W. H.; Berggren, Magnus
  Sensors and Actuators, B: Chemical (2009), 142 (2), 451-456CODEN: SABCEB; ISSN:0925-4005. (Elsevier B.V.)
  Electronically conductive and electrochem. active 3D-scaffolds based on electrospun poly(ethylene terephthalate) (PET) nano-fibers are reported. Vapor phase polymn. was employed to achieve an uniform and conformal coating of poly(3,4-ethylenedioxythiophene) doped with tosylate (PEDOT:tosylate) on the nano-fibers. The PEDOT coatings had a large impact on the wettability, turning the hydrophobic PET fibers super-hydrophilic. SH-SY5Y neuroblastoma cells were grown on the PEDOT coated fibers. The SH-SY5Y cells adhered well and showed healthy morphol. These elec. active scaffolds were used to induce Ca2+ signalling in SH-SY5Y neuroblastoma cells. PEDOT:tosylate coated nano-fibers represent a class of 3D host environments that combines excellent adhesion and proliferation for neuronal cells with the possibility to regulate their signalling.
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46. 46
  Bendrea, A.-D.; Cianga, L.; Cianga, I. Review Paper: Progress in the Field of Conducting Polymers for Tissue Engineering Applications. J. Biomater. Appl. 2011, 26, 3– 84, DOI: 10.1177/0885328211402704
  46
  Review paper: progress in the field of conducting polymers for tissue engineering applications
  Bendrea, Anca-Dana; Cianga, Luminita; Cianga, Ioan
  Journal of Biomaterials Applications (2011), 26 (1), 3-84CODEN: JBAPEL; ISSN:0885-3282. (Sage Publications Ltd.)
  This review focuses on one of the most exciting applications area of conjugated conducting polymers, which is tissue engineering. Strategies used for the biocompatibility improvement of this class of polymers (including biomols.' entrapment or covalent grafting) and also the integrated novel technologies for smart scaffolds generation such as micropatterning, electrospinning, self-assembling are emphasized. These processing alternatives afford the electroconducting polymers nanostructures, the most appropriate forms of the materials that closely mimic the crit. features of the natural extracellular matrix. Due to their capability to electronically control a range of phys. and chem. properties, conducting polymers such as polyaniline, polypyrrole, and polythiophene and/or their derivs. and composites provide compatible substrates which promote cell growth, adhesion, and proliferation at the polymer-tissue interface through elec. stimulation. The activities of different types of cells on these materials are also presented in detail. Specific cell responses depend on polymers surface characteristics like roughness, surface free energy, topog., chem., charge, and other properties as elec. cond. or mech. actuation, which depend on the employed synthesis conditions. The biol. functions of cells can be dramatically enhanced by biomaterials with controlled organizations at the nanometer scale and in the case of conducting polymers, by the elec. stimulation. The advantages of using biocompatible nanostructures of conducting polymers (nanofibers, nanotubes, nanoparticles, and nanofilaments) in tissue engineering are also highlighted.
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47. 47
  Rivers, T. J.; Hudson, T. W.; Schmidt, C. E. Synthesis of a Novel, Biodegradable Electrically Conducting Polymer for Biomedical Applications. Adv. Funct. Mater. 2002, 12, 33, DOI: 10.1002/1616-3028(20020101)12:1<33::aid-adfm33>3.0.co;2-e
  47
  Synthesis of a novel, biodegradable electrically conducting polymer for biomedical applications
  Rivers, Tyrell J.; Hudson, Terry W.; Schmidt, Christine E.
  Advanced Functional Materials (2002), 12 (1), 33-37CODEN: AFMDC6; ISSN:1616-301X. (Wiley-VCH Verlag GmbH)
  The authors reported the synthesis and characterization of a novel biomaterial that possesses the unique properties of being both elec. conducting and biodegradable; and thus capable of electronic interfacing with tissue. This polymer was synthesized from conducting oligomers of pyrrole and thiophene that are connected together via degradable ester linkages. This polymer is conductive, degradable, and biocompatible.
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48. 48
  Huang, L.; Hu, J.; Lang, L.; Wang, X.; Zhang, P.; Jing, X.; Wang, X.; Chen, X.; Lelkes, P. I.; MacDiarmid, A. G. Synthesis and Characterization of Electroactive and Biodegradable ABA Block Copolymer of Polylactide and Aniline Pentamer. Biomaterials 2007, 28, 1741– 1751, DOI: 10.1016/j.biomaterials.2006.12.007
  48
  Synthesis and characterization of electroactive and biodegradable ABA block copolymer of polylactide and aniline pentamer
  Huang, Lihong; Hu, Jun; Lang, Le; Wang, Xin; Zhang, Peibiao; Jing, Xiabin; Wang, Xianhong; Chen, Xuesi; Lelkes, Peter I.; MacDiarmid, Alan G.; Wei, Yen
  Biomaterials (2007), 28 (10), 1741-1751CODEN: BIMADU; ISSN:0142-9612. (Elsevier Ltd.)
  A triblock copolymer PLA-b-AP-b-PLA (PAP) of polylactide (PLA) and aniline pentamer (AP) with the unique properties of being both electroactive and biodegradable is synthesized by coupling an electroactive carboxyl-capped AP with two biodegradable bi-hydroxyl-capped PLAs via a condensation reaction. Three different mol. wt. PAP copolymers are prepd. The PAP copolymers exhibit excellent electroactivity similar to the AP and polyaniline, which may stimulate cell proliferation and differentiation. The elec. cond. of the PAP2 copolymer film (∼5×10-6 S/cm) is in the semiconducting region. Transmission electron microscopic results suggest that there is microphase sepn. of the two block segments in the copolymer, which might contribute to the obsd. cond. The biodegrdn. and biocompatibility expts. in vitro prove the copolymer is biodegradable and biocompatible. Moreover, these new block copolymer shows good soly. in common org. solvents, leading to the system with excellent processibility. These biodegradable PAP copolymers with electroactive function thus possess the properties that would be potentially used as scaffold materials for neuronal or cardiovascular tissue engineering.
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49. 49
  Xie, M.; Wang, L.; Ge, J.; Guo, B.; Ma, P. X. Strong Electroactive Biodegradable Shape Memory Polymer Networks Based on Star-Shaped Polylactide and Aniline Trimer for Bone Tissue Engineering. ACS Appl. Mater. Interfaces 2015, 7, 6772– 6781, DOI: 10.1021/acsami.5b00191
  49
  Strong Electroactive Biodegradable Shape Memory Polymer Networks Based on Star-Shaped Polylactide and Aniline Trimer for Bone Tissue Engineering
  Xie, Meihua; Wang, Ling; Ge, Juan; Guo, Baolin; Ma, Peter X.
  ACS Applied Materials & Interfaces (2015), 7 (12), 6772-6781CODEN: AAMICK; ISSN:1944-8244. (American Chemical Society)
  Prepn. of functional shape memory polymer (SMP) for tissue engineering remains a challenge. Here the synthesis of strong electroactive shape memory polymer (ESMP) networks based on star-shaped polylactide (PLA) and aniline trimer (AT) is reported. Six-armed PLAs with various chain lengths were chem. crosslinked to synthesize SMP. After addn. of an electroactive AT segment into the SMP, ESMP was obtained. The polymers were characterized by 1H NMR, GPC, FT-IR, CV, DSC, DMA, tensile test, and degrdn. test. The SMP and ESMP exhibited strong mech. properties (modulus higher than GPa) and excellent shape memory performance: short recovery time (several seconds), high recovery ratio (over 94%), and high fixity ratio (almost 100%). Moreover, cyclic voltammetry test confirmed the electroactivity of the ESMP. The ESMP significantly enhanced the proliferation of C2C12 cells compared to SMP and linear PLA (control). In addn., the ESMP greatly improved the osteogenic differentiation of C2C12 myoblast cells compared to PH10 and PLA in terms of ALP enzyme activity, immunofluorescence staining, and relative gene expression by quant. real-time polymerase chain reaction (qRT-PCR). These intelligent SMPs and electroactive SMP with strong mech. properties, tunable degradability, good electroactivity, biocompatibility, and enhanced osteogenic differentiation of C2C12 cells show great potential for bone regeneration.
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50. 50
  Dong, R.; Zhao, X.; Guo, B.; Ma, P. X. Self-Healing Conductive Injectable Hydrogels with Antibacterial Activity as Cell Delivery Carrier for Cardiac Cell Therapy. ACS Appl. Mater. Interfaces 2016, 8, 17138– 17150, DOI: 10.1021/acsami.6b04911
  50
  Self-Healing Conductive Injectable Hydrogels with Antibacterial Activity as Cell Delivery Carrier for Cardiac Cell Therapy
  Dong, Ruonan; Zhao, Xin; Guo, Baolin; Ma, Peter X.
  ACS Applied Materials & Interfaces (2016), 8 (27), 17138-17150CODEN: AAMICK; ISSN:1944-8244. (American Chemical Society)
  Cell therapy is a promising strategy to regenerate cardiac tissue for myocardial infarction. Injectable hydrogels with cond. and self-healing ability are highly desirable as cell delivery vehicles for cardiac regeneration. Here, we developed self-healable conductive injectable hydrogels based on chitosan-graft-aniline tetramer (CS-AT) and dibenzaldehyde-terminated poly(ethylene glycol) (PEG-DA) as cell delivery vehicles for myocardial infarction. Self-healed electroactive hydrogels were obtained after mixing CS-AT and PEG-DA solns. at physiol. conditions. Rapid self-healing behavior was investigated by rheometer. Swelling behavior, morphol., mech. strength, electrochem., cond., adhesiveness to host tissue and antibacterial property of the injectable hydrogels were fully studied. Cond. of the hydrogels is ∼10-3 S·cm-1, which is quite close to native cardiac tissue. Proliferation of C2C12 myoblasts in the hydrogel showed its good biocompatibility. After injection, viability of C2C12 cells in the hydrogels showed no significant difference with that before injection. Two different cell types were successfully encapsulated in the hydrogels by self-healing effect. Cell delivery profile of C2C12 myoblasts and H9c2 cardiac cells showed a tunable release rate, and in vivo cell retention in the conductive hydrogels was also studied. S.c. injection and in vivo degrdn. of the hydrogels demonstrated their injectability and biodegradability. Together, these self-healing conductive biodegradable injectable hydrogels are excellent candidates as cell delivery vehicle for cardiac repair.
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51. 51
  Jia, X.; Chao, D.; Berda, E. B.; Pei, S.; Liu, H.; Zheng, T.; Wang, C. Fabrication of Electrochemically Responsive Surface Relief Diffraction Gratings Based on a Multifunctional Polyamide Containing Oligoaniline and Azo Groups. J. Mater. Chem. 2011, 21, 18317, DOI: 10.1039/c1jm14047g
  There is no corresponding record for this reference.
52. 52
  Guo, B.; Finne-Wistrand, A.; Albertsson, A.-C. Universal Two-Step Approach to Degradable and Electroactive Block Copolymers and Networks from Combined Ring-Opening Polymerization and Post-Functionalization via Oxidative Coupling Reactions. Macromolecules 2011, 44, 5227– 5236, DOI: 10.1021/ma2009595
  52
  Universal Two-Step Approach to Degradable and Electroactive Block Copolymers and Networks from Combined Ring-Opening Polymerization and Post-Functionalization via Oxidative Coupling Reactions
  Guo, Baolin; Finne-Wistrand, Anna; Albertsson, Ann-Christine
  Macromolecules (Washington, DC, United States) (2011), 44 (13), 5227-5236CODEN: MAMOBX; ISSN:0024-9297. (American Chemical Society)
  We present a universal strategy for the facile synthesis of degradable and electroactive block copolymers and organogels (DEBCGs) based on aniline oligomers and polyesters in a two-step approach, here exemplified by the prepn. of a series of DECBCGs based on aniline tetramer (AT) and poly(ε-caprolactone) (PCL). Polyesters with an aniline dimer (AD) segment were first obtained by controlled ring-opening polymn. (ROP) of ε-caprolactone initiated by the amine group of AD with or without 2,2-bis(ε-caprolactone-4-yl) propane (BCP). The postpolymn. modification via an oxidative coupling reaction between AD and a polyester was then used to form the electroactive segment AT in the copolymers or organogels. The mol. wt. and cond. of the block copolymers and organogels were controlled by the AT content. The chem. structure, electroactivity, and thermal properties of DEBCGs were investigated by FT-IR, NMR, SEC, UV, cyclic voltammetry, TGA, and DSC. Our general strategy for the synthesis of DECBCGs avoids the multiple step reactions and low efficiency involved in previous work.
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53. 53
  Guo, B.; Finne-Wistrand, A.; Albertsson, A.-C. Simple Route to Size-Tunable Degradable and Electroactive Nanoparticles from the Self-Assembly of Conducting Coil–Rod–Coil Triblock Copolymers. Chem. Mater. 2011, 23, 4045– 4055, DOI: 10.1021/cm201782v
  There is no corresponding record for this reference.
54. 54
  Lin, W.; Fu, Q.; Zhang, Y.; Huang, J. One-Pot Synthesis of ABC Type Triblock Copolymers via a Combination of “Click Chemistry” and Atom Transfer Nitroxide Radical Coupling Chemistry. Macromolecules 2008, 41, 4127– 4135, DOI: 10.1021/ma702404t
  54
  One-Pot Synthesis of ABC Type Triblock Copolymers via a Combination of "Click Chemistry" and Atom Transfer Nitroxide Radical Coupling Chemistry
  Lin, Wencheng; Fu, Qiang; Zhang, Yi; Huang, Junlian
  Macromolecules (Washington, DC, United States) (2008), 41 (12), 4127-4135CODEN: MAMOBX; ISSN:0024-9297. (American Chemical Society)
  A new strategy for one-pot synthesis of ABC type triblock copolymers via a combination of "click chem." and atom transfer nitroxide radical coupling (ATNRC) reaction was suggested, and poly(tert-Bu acrylate)-block-polystyrene-block-poly(ethylene oxide) (PtBA-PS-PEO) and poly(tert-Bu acrylate)-block-polystyrene-block-poly(ε-caprolactone) (PtBA-PS-PCL) were successfully prepd. by this method. The precursors with predetd. no.-av. mol. wt. and low polydispersity indexes, such as PS with α-alkyne and ω-bromine end groups, PtBA with azide end group, PEO and PCL with a 2,2,6,6-tetramethylpiperidine-1-oxyl end group, were directly prepd. by living polymn. technique using the compds. with corresponding functional groups as initiators, and no further modifications of the end groups were needed, except PtBA-N3. The coupling reaction between precursors was carried out in the CuBr/N,N,N',N'',N''-pentamethyldiethylenetriamine system with high efficiencies. The obtained polymers were characterized by FT-IR, 1H NMR, differential scanning calorimetry, and gel permeation chromatog. in detail.
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55. 55
  Guo, B.; Finne-Wistrand, A.; Albertsson, A.-C. Degradable and Electroactive Hydrogels with Tunable Electrical Conductivity and Swelling Behavior. Chem. Mater. 2011, 23, 1254– 1262, DOI: 10.1021/cm103498s
  55
  Degradable and Electroactive Hydrogels with Tunable Electrical Conductivity and Swelling Behavior
  Guo, Baolin; Finne-Wistrand, Anna; Albertsson, Ann-Christine
  Chemistry of Materials (2011), 23 (5), 1254-1262CODEN: CMATEX; ISSN:0897-4756. (American Chemical Society)
  Degradable elec. conducting hydrogels (DECHs), which combine the unique properties of degradable polymers and elec. conducting hydrogels, were synthesized by introducing biodegradable segments into conductive hydrogels. These DECHs were obtained by joining together the photopolymd. macromer acrylated poly(D,L-lactide)-poly(ethylene glycol)-poly(D,L-lactide) (AC-PLA-PEG-PLA-AC), glycidyl methacrylate (GMA), ethylene glycol dimethacrylate (EGDMA) network and aniline tetramer (AT) by the coupling reaction between AT and the GMA. The elec. cond. and swelling behavior of these DECHs were tuned by changing the AT content in the hydrogels, the crosslinking degree, and the environmental pH value. The good electroactivity and thermal stability of these hydrogels were demonstrated by UV-vis spectroscopy, cyclic voltammetry, and TGA tests. The chem. structure and morphol. of these polymers were characterized by NMR, FT-IR, SEC, and SEM. These hydrogels possessing both degradability and elec. cond. represent a new class of biomaterial and will lead to various new possibilities in biomedical applications.
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56. 56
  Borriello, A.; Guarino, V.; Schiavo, L.; Alvarez-Perez, M. A.; Ambrosio, L. Optimizing PANi Doped Electroactive Substrates as Patches for the Regeneration of Cardiac Muscle. J. Mater. Sci.: Mater. Med. 2011, 22, 1053– 1062, DOI: 10.1007/s10856-011-4259-x
  56
  Optimizing PANi doped electroactive substrates as patches for the regeneration of cardiac muscle
  Borriello, A.; Guarino, V.; Schiavo, L.; Alvarez-Perez, M. A.; Ambrosio, L.
  Journal of Materials Science: Materials in Medicine (2011), 22 (4), 1053-1062CODEN: JSMMEL; ISSN:0957-4530. (Springer)
  In scaffold aided regeneration of muscular tissue, composite materials are currently utilized as a temporary substrate to stimulate tissue formation by controlled electrochem. signals as well as continuous mech. stimulation until the regeneration processes are completed. Among them, composites from the blending of conductive (CPs) and biocompatible polymers are powerfully emerging as a successful strategy for the regeneration of myocardium due to their unique conductive and biol. recognition properties able to assure a more efficient electroactive stimulation of cells. Here, different composite substrates made of synthesized polyaniline (sPANi) and polycaprolactone (PCL) were investigated as platforms for cardiac tissue regeneration. Preliminary, a comparative anal. of substrates cond. performed on casted films endowed with synthesized polyaniline (sPANi) short fibers or blended with emeraldine base polyaniline (EBPANi) allows to study the attitude of charge transport, depending on the conducting filler amt., shape and spatial distribution. In particular, conductibility tests indicated that sPANi short fibers provide a more efficient transfer of elec. signal due to the spatial organization of electroactive needle-like phases up to form a percolative network. On the basis of this characterization, sPANi/PCL electrospun membranes have been also optimized to mimic either the morphol. and functional features of the cardiac muscle ECM. The presence of sPANi does not relevantly affect the fiber architecture as confirmed by SEM/image anal. investigation which shows a broader distribution of fibers with only a slight redn. of the av. fiber diam. from 7.1 to 6.4 μm. Meanwhile, biol. assays-evaluation of cell survival rate by MTT assay and immunostaining of sarcomeric α-actinin of cardiomyocytes-like cells-clearly indicate that conductive signals offered by PANi needles, promote the cardiogenic differentiation of hMSC into cardiomyocyte-like cells. These preliminary results concur to promise the development of electroactive biodegradable substrates able to efficiently stimulate the basic cell mechanisms, paving the way towards a new generation of synthetic patches for the support of the regeneration of damaged myocardium.
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57. 57
  Wang, H.-j.; Ji, L.-w.; Li, D.-f.; Wang, J.-Y. Characterization of Nanostructure and Cell Compatibility of Polyaniline Films with Different Dopant Acids. J. Phys. Chem. B 2008, 112, 2671– 2677, DOI: 10.1021/jp0750957
  57
  Characterization of Nanostructure and Cell Compatibility of Polyaniline Films with Different Dopant Acids
  Wang, Hua-jie; Ji, Li-wen; Li, Da-feng; Wang, Jin-Ye
  Journal of Physical Chemistry B (2008), 112 (9), 2671-2677CODEN: JPCBFK; ISSN:1520-6106. (American Chemical Society)
  Polyaniline (PANi) films were prepd. by direct polymg. deposition with four different kinds of acids as dopants or were prepd. by a casting method on the surface of a polytetrafluoroethylene substrate. The properties of PANi films were characterized using at. force microscopy, elec. cond. measurements, and water contact angle measurements. Unlike the casting PANi film, exptl. results indicated that the synthesized PANi films had a similar nanostructure as that of av. nanoparticles (approx. diam. of 30-50 nm). To investigate the potential usefulness of PANi films in biomedical applications, we also studied their biocompatibility through the adhesion and proliferation properties of PC-12 pheochromocytoma cells. All the films were found to be biocompatible and allowed cell attachment and proliferation. However, the synthesized films have a much higher ability for cell adhesion than the casting film. After 4 days of culture on different PANi films, the cells formed more confluent monolayers on the synthesized PANi films than on the casting films. These results demonstrate that the PANi films could be used to culture neurotic cells and that their surface architecture on the nanoscale may affect cell function such as attachment and proliferation.
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58. 58
  Bober, P.; Humpolíček, P.; Pacherník, J.; Stejskal, J.; Lindfors, T. Conducting Polyaniline Based Cell Culture Substrate for Embryonic Stem Cells and Embryoid Bodies. RSC Adv. 2015, 5, 50328– 50335, DOI: 10.1039/c5ra07504a
  58
  Conducting polyaniline based cell culture substrate for embryonic stem cells and embryoid bodies
  Bober, Patrycja; Humpolicek, Petr; Pachernik, Jiri; Stejskal, Jaroslav; Lindfors, Tom
  RSC Advances (2015), 5 (62), 50328-50335CODEN: RSCACL; ISSN:2046-2069. (Royal Society of Chemistry)
  In this work, thin films consisting of elec. conducting polyaniline (PANI) and poly(2-acrylamido-2-methyl-1-propanesulfonate) (PAMPSA) have been used as cell culture substrates for embryonic stem cells (ESC) and embryoid bodies (EMB). The PANI-PAMPSA films having fibrillar morphol. were electrochem. polymd. in a single-step by cyclic voltammetry from an aq. soln. contg. aniline and PAMPSA. UV-visible spectroscopy showed that the PANI films were elec. conducting still at pH 10. This makes them suitable for tissue engineering applications operating at physiol. pH, in contrast to the commonly used PANI hydrochloride films which loose their elec. cond. at pH ≥ 4. Our results reveal that the PANI-PAMPSA films allow only for limited ESC adhesion and growth. The inhibition of the EMB growth and adhesion on the PANI-PAMPSA surface in serum-free medium indicates that it can be used as a cell-selective substrate for the growth of only some specific differentiated EMB cell types.
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59. 59
  Strakosas, X.; Wei, B.; Martin, D. C.; Owens, R. M. Biofunctionalization of Polydioxythiophene Derivatives for Biomedical Applications. J. Mater. Chem. B 2016, 4, 4952– 4968, DOI: 10.1039/c6tb00852f
  59
  Biofunctionalization of polydioxythiophene derivatives for biomedical applications
  Strakosas, Xenofon; Wei, Bin; Martin, David C.; Owens, Roisin M.
  Journal of Materials Chemistry B: Materials for Biology and Medicine (2016), 4 (29), 4952-4968CODEN: JMCBDV; ISSN:2050-7518. (Royal Society of Chemistry)
  The polydioxythiophenes PEDOT and more recently ProDOT have emerged as champion materials in the field of org. bioelectronics, both in the domain of biosensing and also for integration with living cells (both in vitro and in vivo). Although polydioxythiophenes in their pristine forms have shown great promise for bioelectronics, in order to broaden the spectrum of applications, a biofunctionalization step is essential. In this review we summarise the methods that have been used thus far to biofunctionalize polydioxythiophenes in an effort to improve the biotic/abiotic interface. We provide an introduction to this class of materials, focusing particularly on the different methods of synthesis (chem. oxidative polymn., vapor phase polymn. or direct electrochem. polymn.) and discuss the implications of synthesis on biofunctionalization. Rather than provide an exhaustive review, we chose to highlight key examples of biofunctionalization techniques for polydioxythiophenes for specific biomedical applications. Finally, we conclude with a brief discussion of the importance of biofunctionalization methods in future bioelectronics applications, and some ideas for future directions in this field.
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60. 60
  Mantione, D.; del Agua, I.; Sanchez-Sanchez, A.; Mecerreyes, D. Poly(3,4-Ethylenedioxythiophene) (PEDOT) Derivatives: Innovative Conductive Polymers for Bioelectronics. Polymers 2017, 9, 354, DOI: 10.3390/polym9080354
  60
  Poly(3,4-ethylenedioxythiophene) (PEDOT) derivatives: innovative conductive polymers for bioelectronics
  Mantione, Daniele; del Agua, Isabel; Sanchez-Sanchez, Ana; Mecerreyes, David
  Polymers (Basel, Switzerland) (2017), 9 (8), 354/1-354/21CODEN: POLYCK; ISSN:2073-4360. (MDPI AG)
  A review. Poly(3,4-ethylenedioxythiophene)s are the conducting polymers (CP) with the biggest prospects in the field of bioelectronics due to their combination of characteristics (cond., stability, transparency and biocompatibility). The gold std. material is the com. available poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS). However, in order to well connect the two fields of biol. and electronics, PEDOT:PSS presents some limitations assocd. with its low (bio)functionality. In this review, we provide an insight into the synthesis and applications of innovative poly(ethylenedioxythiophene)-type materials for bioelectronics. First, we present a detailed anal. of the different synthetic routes to (bio)functional dioxythiophene monomer/polymer derivs. Second, we focus on the prepn. of PEDOT dispersions using different biopolymers and biomols. as dopants and stabilizers. To finish, we review the applications of innovative PEDOT-type materials such as biocompatible conducting polymer layers, conducting hydrogels, biosensors, selective detachment of cells, scaffolds for tissue engineering, electrodes for electrophysiol., implantable electrodes, stimulation of neuronal cells or pan-bio electronics.
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61. 61
  Povlich, L. K.; Cho, J. C.; Leach, M. K.; Corey, J. M.; Kim, J.; Martin, D. C. Synthesis, Copolymerization and Peptide-Modification of Carboxylic Acid-Functionalized 3,4-Ethylenedioxythiophene (EDOTacid) for Neural Electrode Interfaces. Biochim. Biophys. Acta, Gen. Subj. 2013, 1830, 4288– 4293, DOI: 10.1016/j.bbagen.2012.10.017
  61
  Synthesis, copolymerization and peptide-modification of carboxylic acid-functionalized 3,4-ethylenedioxythiophene (EDOTacid) for neural electrode interfaces
  Povlich, Laura K.; Cho, Jae Cheol; Leach, Michelle K.; Corey, Joseph M.; Kim, Jinsang; Martin, David C.
  Biochimica et Biophysica Acta, General Subjects (2013), 1830 (9), 4288-4293CODEN: BBGSB3; ISSN:0304-4165. (Elsevier B.V.)
  Conjugated polymers have been developed as effective materials for interfacing prosthetic device electrodes with neural tissue. Recent focus has been on the development of conjugated polymers that contain biol. components in order to improve the tissue response upon implantation of these electrodes. Carboxylic acid-functionalized 3,4-ethylenedioxythiophene (EDOTacid) monomer was synthesized in order to covalently bind peptides to the surface of conjugated polymer films. EDOTacid was copolymd. with EDOT monomer to form stable, elec. conductive copolymer films referred to as PEDOT-PEDOTacid. The peptide GGGGRGDS was bound to PEDOT-PEDOTacid to create peptide functionalized PEDOT films. The PEDOT-PEDOTacid-peptide films increased the adhesion of primary rat motor neurons between 3 and 9 times higher than controls, thus demonstrating that the peptide maintained its biol. activity. The EDOT-acid monomer can be used to create functionalized PEDOT-PEDOTacid copolymer films that can have controlled bioactivity. PEDOT-PEDOTacid-peptide films have the potential to control the behavior of neurons and vastly improve the performance of implanted electrodes. This article is part of a Special Issue entitled Org. Bioelectronics-Novel Applications in Biomedicine.
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62. 62
  Wei, B.; Liu, J.; Ouyang, L.; Kuo, C.-C.; Martin, D. C. Significant Enhancement of PEDOT Thin Film Adhesion to Inorganic Solid Substrates with EDOT-Acid. ACS Appl. Mater. Interfaces 2015, 7, 15388– 15394, DOI: 10.1021/acsami.5b03350
  62
  Significant Enhancement of PEDOT Thin Film Adhesion to Inorganic Solid Substrates with EDOT-Acid
  Wei, Bin; Liu, Jinglin; Ouyang, Liangqi; Kuo, Chin-Chen; Martin, David C.
  ACS Applied Materials & Interfaces (2015), 7 (28), 15388-15394CODEN: AAMICK; ISSN:1944-8244. (American Chemical Society)
  With its high cond., tunable surface morphol., relatively soft mech. response, high chem. stability, and excellent biocompatibility, poly(3,4-ethylenedioxythiophene) (PEDOT) has become a promising coating material for a variety of electronic biomedical devices. However, the relatively poor adhesion of PEDOT to inorg. metallic and semiconducting substrates still poses challenges for long-term applications. Here, we report that 2,3-dihydrothieno(3,4-b)(1,4)dioxine-2-carboxylic acid (EDOT-acid) significantly improves the adhesion between PEDOT thin films and inorg. solid electrodes. EDOT-acid mols. were chem. bonded onto activated oxide substrates via the chemisorption of the carboxylic groups. PEDOT was then polymd. onto the EDOT-acid modified substrates, forming covalently bonded coatings. The adsorption of EDOT-acid onto the electrode surfaces was characterized by cyclic voltammetry (CV), contact angle measurements, at. force microscopy, and XPS. The elec. properties of the subsequently coated PEDOT films were studied by electrochem. impedance spectroscopy and CV. An aggressive ultrasonication test confirmed the significantly improved adhesion and mech. stability of the PEDOT films on electrodes with EDOT-acid treatment over those without treatment.
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63. 63
  Mawad, D.; Artzy-Schnirman, A.; Tonkin, J.; Ramos, J.; Inal, S.; Mahat, M. M.; Darwish, N.; Zwi-Dantsis, L.; Malliaras, G. G.; Gooding, J. J. Electroconductive Hydrogel Based on Functional Poly(Ethylenedioxy Thiophene). Chem. Mater. 2016, 28, 6080– 6088, DOI: 10.1021/acs.chemmater.6b01298
  63
  Electroconductive Hydrogel Based on Functional Poly(Ethylenedioxy Thiophene)
  Mawad, Damia; Artzy-Schnirman, Arbel; Tonkin, Joanne; Ramos, Jose; Inal, Sahika; Mahat, Muzamir M.; Darwish, Nadim; Zwi-Dantsis, Limor; Malliaras, George G.; Gooding, J. Justin; Lauto, Antonio; Stevens, Molly M.
  Chemistry of Materials (2016), 28 (17), 6080-6088CODEN: CMATEX; ISSN:0897-4756. (American Chemical Society)
  Poly(ethylene dioxythiophene) with functional pendant groups bearing double bonds is synthesized and employed for the fabrication of electroactive hydrogels with advantageous characteristics; covalently crosslinked porous 3D scaffolds with notable swelling ratio, appropriate mech. properties, electroactive in physiol. conditions, and suitable for pro-liferation and differentiation of C2C12 cells. This is a new approach for the fabrication of conductive engineered constructs.
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64. 64
  Zhu, B.; Luo, S.-C.; Zhao, H.; Lin, H.-A.; Sekine, J.; Nakao, A.; Chen, C.; Yamashita, Y.; Yu, H.-h. Large Enhancement in Neurite Outgrowth on a Cell Membrane-Mimicking Conducting Polymer. Nat. Commun. 2014, 5, 4523, DOI: 10.1038/ncomms5523
  64
  Large enhancement in neurite outgrowth on a cell membrane-mimicking conducting polymer
  Zhu, Bo; Luo, Shyh-Chyang; Zhao, Haichao; Lin, Hsing-An; Sekine, Jun; Nakao, Aiko; Chen, Chi; Yamashita, Yoshiro; Yu, Hsiao-hua
  Nature Communications (2014), 5 (), 4523CODEN: NCAOBW; ISSN:2041-1723. (Nature Publishing Group)
  Although elec. stimulated neurite outgrowth on bioelectronic devices is a promising means of nerve regeneration, immunogenic scar formation can insulate electrodes from targeted cells and tissues, thereby reducing the lifetime of the device. Ideally, an electrode material capable of elec. interfacing with neurons selectively and efficiently would be integrated without being recognized by the immune system and minimize its response. Here we develop a cell membrane-mimicking conducting polymer possessing several attractive features. This polymer displays high resistance towards nonspecific enzyme/cell binding and recognizes targeted cells specifically to allow intimate elec. communication over long periods of time. Its low elec. impedance relays elec. signals efficiently. This material is capable to integrate biochem. and elec. stimulation to promote neural cellular behavior. Neurite outgrowth is enhanced greatly on this new conducting polymer; in addn., elec. stimulated secretion of proteins from primary Schwann cells can also occur on it.
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65. 65
  Wang, S.; Guan, S.; Wang, J.; Liu, H.; Liu, T.; Ma, X.; Cui, Z. Fabrication and Characterization of Conductive Poly (3,4-Ethylenedioxythiophene) Doped with Hyaluronic Acid/poly (L-Lactic Acid) Composite Film for Biomedical Application. J. Biosci. Bioeng. 2017, 123, 116– 125, DOI: 10.1016/j.jbiosc.2016.07.010
  65
  Fabrication and characterization of conductive poly (3,4-ethylenedioxythiophene) doped with hyaluronic acid/poly (L-lactic acid) composite film for biomedical application
  Wang, Shuping; Guan, Shui; Wang, Jing; Liu, Hailong; Liu, Tianqing; Ma, Xuehu; Cui, Zhanfeng
  Journal of Bioscience and Bioengineering (2017), 123 (1), 116-125CODEN: JBBIF6; ISSN:1347-4421. (Society for Biotechnology, Japan)
  Poly 3,4-ethylenedioxythiophene (PEDOT), a polythiophene deriv., has been proved to be modified by chem. process as biocompatible conductive polymer for biomedical applications. In this study, novel hyaluronic acid (HA)-doped PEDOT nanoparticles were synthesized by the method of chem. oxidative polymn., then conductive PEDOT-HA/poly(L-lactic acid) (PLLA) composite films were prepd. The physicochem. characteristics and biocompatibility of films were further investigated. FTIR, Raman and EDX anal. demonstrated that HA was successfully doped into PEDOT particles. Cyclic voltammograms indicated PEDOT-HA particles had favorable electrochem. stability. PEDOT-HA/PLLA films showed lower surface contact angle and faster degrdn. degree compared with PLLA films. Moreover, the cytotoxicity test of PEDOT-HA/PLLA films showed that neuron-like pheochromocytoma (PC12) cells adhered and spread well on the surface of PEDOT-HA/PLLA films and cell viability denoted by MTT assay had a significant increase. PEDOT-HA/PLLA films modified with laminin (LN) also exhibited an efficiently elongated cell morphol. obsd. by fluorescent microscope and metallog. microscope. Furthermore, PEDOT-HA/PLLA films were subjected to different current intensity to elucidate the effect of elec. stimulation (ES) on neurite outgrowth of PC12 cells. ES (0.5 mA, 2 h) significantly promoted neurite outgrowth with an av. value length of 122 ± 5 μm and enhanced the mRNA expression of growth-assocd. protein (GAP43) and synaptophysin (SYP) in PC12 cells when compared with other ES groups. These results suggest that PEDOT-HA/PLLA film combined with ES are conducive to cell growth and neurite outgrowth, indicating the conductive PEDOT-HA/PLLA film may be an attractive candidate with ES for enhancing nerve regeneration in nerve tissue engineering.
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66. 66
  Xu, H.; Holzwarth, J. M.; Yan, Y.; Xu, P.; Zheng, H.; Yin, Y.; Li, S.; Ma, P. X. Conductive PPY/PDLLA Conduit for Peripheral Nerve Regeneration. Biomaterials 2014, 35, 225– 235, DOI: 10.1016/j.biomaterials.2013.10.002
  66
  Conductive PPY/PDLLA conduit for peripheral nerve regeneration
  Xu, Haixing; Holzwarth, Jeremy M.; Yan, Yuhua; Xu, Peihu; Zheng, Hua; Yin, Yixia; Li, Shipu; Ma, Peter X.
  Biomaterials (2014), 35 (1), 225-235CODEN: BIMADU; ISSN:0142-9612. (Elsevier Ltd.)
  The significant drawbacks and lack of success assocd. with current methods to treat critically sized nerve defects have led to increased interest in neural tissue engineering. Conducting polymers show great promise due to their elec. properties, and in the case of polypyrrole (PPY), its cell compatibility as well. Thus, the goal of this study is to synthesize a conducting composite nerve conduit with PPY and poly(D, L-lactic acid) (PDLLA), assess its ability to support the differentiation of rat pheochromocytoma 12 (PC12) cells in vitro, and det. its ability to promote nerve regeneration in vivo. Different amts. of PPY (5%, 10%, and 15%) are used to synthesize the conduits resulting in different conductivities (5.65, 10.40, and 15.56 ms/cm, resp.). When PC12 cells are seeded on these conduits and stimulated with 100 mV for 2 h, there is a marked increase in both the percentage of neurite-bearing cells and the median neurite length as the content of PPY increased. More importantly, when the PPY/PDLLA nerve conduit was used to repair a rat sciatic nerve defect it performed similarly to the gold std. autologous graft. These promising results illustrate the potential that this PPY/PDLLA conducting composite conduit has for neural tissue engineering.
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67. 67
  Planellas, M.; Pérez-Madrigal, M. M.; del Valle, L. J.; Kobauri, S.; Katsarava, R.; Alemán, C.; Puiggalí, J. Microfibres of Conducting Polythiophene and Biodegradable Poly(ester Urea) for Scaffolds. Polym. Chem. 2015, 6, 925– 937, DOI: 10.1039/c4py01243g
  67
  Microfibres of conducting polythiophene and biodegradable poly(ester urea) for scaffolds
  Planellas, Marc; Perez-Madrigal, Maria M.; del Valle, Luis J.; Kobauri, Sophio; Katsarava, Ramaz; Aleman, Carlos; Puiggali, Jordi
  Polymer Chemistry (2015), 6 (6), 925-937CODEN: PCOHC2; ISSN:1759-9962. (Royal Society of Chemistry)
  Hybrid scaffolds constituted of a mixt. of conducting and biodegradable polymers are obtained by the electrospinning technique. Specifically, poly(3-thiophene Me acetate) (P3TMA) and a copolymer derived from L-leucine, which bears ester, urea and amide groups (PEU-co-PEA), have been employed. Both polymers were selected because of their intrinsic properties and their high soly. in org. solvents. The biodegradable polymer renders continuous and homogeneous microfibers under most of the electrospinning conditions tested, appearing to be an ideal carrier for the polythiophene deriv. A spontaneous phase sepn. has been obsd. for concd. solns. of PEU-co-PEA and P3TMA in chloroform-methanol mixts. An enriched dense phase results on the conducting polymer and can be successfully electrospun, giving rise to scaffolds with up to 90 wt% of P3TMA. Morphol. observations have indicated that continuous and regular microfibers are attained despite the high conducting polymer content. P3TMA presents a high doping level and leads to stable electrospun scaffolds by the simple addn. of a low percentage of a high mol. wt. carrier. The resulting scaffolds are practically amorphous and thermally stable, also presenting a pronounced electrochem. response and being electrochem. active. Thus, the formation of polarons and bipolarons at specific positions, the ability to exchange charge reversibly and the elec. stability of hybrid PEU-co-PEA/P3TMA electrospun scaffolds and P3TMA alone are practically the same.
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68. 68
  Huang, L.; Zhuang, X.; Hu, J.; Lang, L.; Zhang, P.; Wang, Y.; Chen, X.; Wei, Y.; Jing, X. Synthesis of Biodegradable and Electroactive Multiblock Polylactide and Aniline Pentamer Copolymer for Tissue Engineering Applications. Biomacromolecules 2008, 9, 850– 858, DOI: 10.1021/bm7011828
  68
  Synthesis of biodegradable and electroactive multiblock polylactide and aniline pentamer copolymer for tissue engineering applications
  Huang, Lihong; Zhuang, Xiuli; Hu, Jun; Lang, Le; Zhang, Peibiao; Wang, Yu; Chen, Xuesi; Wei, Yen; Jing, Xiabin
  Biomacromolecules (2008), 9 (3), 850-858CODEN: BOMAF6; ISSN:1525-7797. (American Chemical Society)
  To obtain one biodegradable and electroactive polymer as the scaffold for tissue engineering, the multiblock copolymer PLAAP was designed and synthesized with the condensation polymn. of hydroxyl-capped poly(L-lactide) (PLA) and carboxyl-capped aniline pentamer (AP). The PLAAP copolymer exhibited excellent electroactivity, soly., and biodegradability. At the same time, as one scaffold material, PLAAP copolymer possesses certain mech. properties with the tensile strength of 3 MPa, tensile Young's modulus of 32 MPa, and breaking elongation rate of 95%. We systematically studied the compatibility of PLAAP copolymer in vitro and proved that the electroactive PLAAP copolymer was innocuous, biocompatible, and helpful for the adhesion and proliferation of rat C6 cells. Moreover, the PLAAP copolymer stimulated by elec. signals was demonstrated as accelerating the differentiation of rat neuronal pheochromocytoma PC-12 cells. This biodegradable and electroactive PLAAP copolymer thus possessed the properties in favor of the long-time application in vivo as nerve repair scaffold materials in tissue engineering.
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69. 69
  Zotti, G.; Zecchin, S.; Schiavon, G.; Louwet, F.; Groenendaal, L.; Crispin, X.; Osikowicz, W.; Salaneck, W.; Fahlman, M. Electrochemical and XPS Studies toward the Role of Monomeric and Polymeric Sulfonate Counterions in the Synthesis, Composition, and Properties of Poly(3,4-Ethylenedioxythiophene). Macromolecules 2003, 36, 3337– 3344, DOI: 10.1021/ma021715k
  69
  Electrochemical and XPS Studies toward the Role of Monomeric and Polymeric Sulfonate Counterions in the Synthesis, Composition, and Properties of Poly(3,4-ethylenedioxythiophene)
  Zotti, G.; Zecchin, S.; Schiavon, G.; Louwet, F.; Groenendaal, L.; Crispin, X.; Osikowicz, W.; Salaneck, W.; Fahlman, M.
  Macromolecules (2003), 36 (9), 3337-3344CODEN: MAMOBX; ISSN:0024-9297. (American Chemical Society)
  Electrochem. prepd. poly(3,4-ethylenedioxythiophene) (PEDT) poly(styrene sulfonate) (PSS), produced from acidic (PSSH) and basic (PSSNa) PSS, were characterized by cyclic voltammetry CV, UV-vis spectroscopy, in situ cond., and XPS spectroscopy and compared with electrochem. prepd. PEDT/tosylate and chem. prepd. PEDT/PSS. The CV data shows that the polymer synthesis is strongly affected by the nucleophilic character of the counter-anion. Although CV and UV-vis spectroscopy show that the structure and d.p. (oligomeric, ca. 10 EDT units) of the PEDT backbone is the same for all polymers, XPS data provide clarification on different cond. obsd. for these materials (1 S cm-1 for PEDT/PSSNa to 400-450 S cm-1 for PEDT/tosylate) based on doping level and compn. The ratio between sulfonate and thiophene units in the polymer is an important factor; the higher the PEDT concn., the higher the cond. The XPS data also clarify the solvent-induced nanometer-scale segregation between PEDT/PSS and excess PSS particles, the often reported cond. enhancement of chem. prepd. PEDT/PSS upon treatment with polar solvents.
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70. 70
  MacDiarmid, A. G.; Zhou, Y.; Feng, J. Oligomers and Isomers: New Horizons in Poly-Anilines. Synth. Met. 1999, 100, 131– 140, DOI: 10.1016/s0379-6779(98)00164-7
  70
  Oligomers and isomers: new horizons in poly-anilines
  MacDiarmid, Alan G.; Zhou, Yao; Feng, Jing
  Synthetic Metals (1999), 100 (1), 131-140CODEN: SYMEDZ; ISSN:0379-6779. (Elsevier Science S.A.)
  The role of isomers in detg. the electronic, magnetic, optical, structural, and mech. properties of polyanilines, including polyaniline was studied. Known types of isomers, i.e., positional, cis/trans, rotational, and isomerization processes, some of which occur relatively slowly even at room temp. in soln. are described. Approaches for detg. the intrinsic properties of polyaniline by isolating the polymer preferably in one isomeric form or as a mixt. contg. a smaller than usual no. of different isomers are outlined.
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71. 71
  Elliott, B. J.; Ellis, W. W.; Luebben, S. D.; Sapp, S. A.; Chang, C.-H.; D’Sa, R. Electrically Conducting Materials from Branched End-Capping Intermediates. U.S. Patent 7,361,728 B1, 2004.
  There is no corresponding record for this reference.
72. 72
  MacDiarmid, A. G. Polyaniline and Polypyrrole: Where Are We Headed?. Synth. Met. 1997, 84, 27– 34, DOI: 10.1016/s0379-6779(97)80658-3
  72
  Polyaniline and polypyrrole: where are we headed?
  MacDiarmid, Alan G.
  Synthetic Metals (1997), 84 (1-3), 27-34CODEN: SYMEDZ; ISSN:0379-6779. (Elsevier)
  A review with 33 refs. The tremendous advances made during the past decade in the chem., electrochem., physics, theory and processing of polyaniline and polypyrrole and their derivs. provide a broad solid foundation for future studies and technol. applications. Selected examples of recent progress are illustrated by: (i) the synthesis of polyaniline oligomers and chiral polyaniline films, (ii) use of polyaniline in light-emitting devices, (iii) effect of substrate surface on properties of polyaniline and polypyrrole films deposited upon them, (i.v.) use of polypyrrole films in flexible, liq. crystal light valves, (v) prepn. of patterned polyaniline and polypyrrole films by microcontact printing and (vi) application of sol. polypyrrole in sensors for volatile org. compds.
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73. 73
  Avlyanov, J. K.; Min, Y.; MacDiarmid, A. G.; Epstein, A. J. Polyaniline: Conformational Changes Induced in Solution by Variation of Solvent and Doping Level. Synth. Met. 1995, 72, 65– 71, DOI: 10.1016/0379-6779(94)02318-s
  73
  Polyaniline: conformational changes induced in solution by variation of solvent and doping level
  Avlyanov, Jamshid K.; Min, Yonggang; MacDiarmid, Alan G.; Epstein, Arthur J.
  Synthetic Metals (1995), 72 (1), 65-71CODEN: SYMEDZ; ISSN:0379-6779. (Elsevier)
  The reduced viscosity of mixts. of polyaniline (emeraldine base, EB) and d, l-camphorsulfonic acid (HCSA) in solns. of m-cresol or chloroform (or in mixts. of these solvents) was investigated. Viscosity measurements as a function of (a) increasing m-cresol content in the mixed solvent for a fully protonated 'EBH+/CSA-' polymer, and (b) increasing protonation level of EB by increasing amts. of HCSA in m-cresol, indicate that the fully protonated polymer adopts a maximized expanded mol. conformation in a good solvent such as m-cresol. These results suggest that the greatly different conductivities obtained for 'EBH+/CSA-' films cast from m-cresol or chloroform solns. result primarily from their different mol. conformations in these solvents.
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74. 74
  da Silva, A. C.; Augusto, T.; Andrade, L. H.; de Torresi, S. I. C. One Pot Biocatalytic Synthesis of a Biodegradable Electroactive Macromonomer Based on 3,4-Ethylenedioxytiophene and Poly(L-Lactic Acid). Mater. Sci. Eng., C 2018, 83, 35– 43, DOI: 10.1016/j.msec.2017.09.007
  74
  One pot biocatalytic synthesis of a biodegradable electroactive macromonomer based on 3,4-ethylenedioxytiophene and poly(L-lactic acid)
  da Silva, Arua C.; Augusto, Tatiana; Andrade, Leandro H.; Cordoba de Torresi, Susana I.
  Materials Science & Engineering, C: Materials for Biological Applications (2018), 83 (), 35-43CODEN: MSCEEE; ISSN:0928-4931. (Elsevier B.V.)
  A novel electroactive macromonomer based on poly(L-lactic acid) (PLLA) with (3,4-ethylenedioxythiophene) (EDOT) functional end groups, was prepd. by a traditional approach of organometallic polymn. with stannous octanoate [Sn(oct2)] and enzymic polymn. using immobilized Candida antarctica Lipase B (CAL-B) and Amano lipase Pseudomonas cepacia(PS-IM), as catalysts. In the synthetic strategy, (2,3-dihydrothieno[3,4-b] dioxin-2-yl)methanol (EDOT-OH) was used to initiate the ring opening polymn. of lactide to yield PLLA with EDOT end group. All macromonomers (EDOT-PLLA) were characterized by 1H and 13C RMN, MALDI-TOF, GPC and EDX. Moreover, ICP-OES anal. showed the presence of Sn traces in the material synthesized by the traditional approach, but that pathway led to macromonomers with higher mol. wt. while the enzymic route led to completely metal-free macromonomers with medium and lower mol. wts. Also, electrochem. and chem. polymn. of EDOT-PLLA were tested showing that it is possible to prep. degradable conducting polymers based on poly(3,4-ethylenedioxythiphene) (PEDOT). The biocatalytic synthesis is a very promising and environmental friendly pathway for the prepn. of biodegradable materials for short time applications.
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75. 75
  Betzel, C.; Singh, T. P.; Visanji, M.; Peters, K.; Fittkau, S.; Saenger, W.; Wilson, K. S. Structure of the Complex of Proteinase K with a Substrate Analogue Hexapeptide Inhibitor at 2.2-A Resolution. J. Biol. Chem. 1993, 268, 15854– 15858
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76. 76
  Singh, N. K.; Singh, S. K.; Dash, D.; Gonugunta, P.; Misra, M.; Maiti, P. CNT Induced β-Phase in Polylactide: Unique Crystallization, Biodegradation, and Biocompatibility. J. Phys. Chem. C 2013, 117, 10163– 10174, DOI: 10.1021/jp4009042
  76
  CNT Induced β-Phase in Polylactide: Unique Crystallization, Biodegradation, and Biocompatibility
  Singh, Narendra K.; Singh, Sunil K.; Dash, Debabrata; Gonugunta, Prasad; Misra, Manjusri; Maiti, Pralay
  Journal of Physical Chemistry C (2013), 117 (19), 10163-10174CODEN: JPCCCK; ISSN:1932-7447. (American Chemical Society)
  The effect of multi-walled carbon nanotube (MWCNT) on the crystal structure, unique crystn., mech. behavior, enzymic degrdn., and significant improvement in biocompatibility of polylactide (PLA) nanohybrid has been reported. Functionalization of carbon nanotube using stearyl alc. has been carried out and has been confirmed through FTIR and Raman spectroscopy. PLA nanohybrids have been synthesized using functionalized and neat MWCNT through soln. route, and the improved level of dispersion of MWCNT has been achieved in PLA matrix. High-magnification transmission electron microscope images indicate the unique adsorption of PLA chain leading to the crystn. of β-phase structure on the surface of the functionalized MWCNT against the usual crystd. α-form of pure PLA. The presence of β phase in nanohybrids has been confirmed through electron diffraction pattern, differential scanning calorimetry thermograms, and X-ray diffraction patterns. The improved and diverse mech., thermal properties, and crystn. kinetics have been explored with the special emphasis on the relaxation behavior of β phase in dynamic mech. anal. The cause of these developments has been appraised from the interaction point of view as calcd. from the interaction parameter (χ) using melting-point depression technique. The rate of biodegrdn. has been studied in detail with plausible mechanism in Proteinase K enzyme media showing their specificity and tuning of biodegrdn. rate followed by their optimization. For biomedical applications, the effect of pure polymer and nanohybrids on circulating blood cells has been evaluated in detail, and the hemocompatible nature of the nanohybrids has been revealed, suppressing the cellular toxicity of MWCNT.
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77. 77
  Morihara, K.; Tsuzuki, H. Specificity of Proteinase K from Tritirachium Album Limber for Synthetic Peptides. Agric. Biol. Chem. 1975, 39, 1489– 1492, DOI: 10.1271/bbb1961.39.1489
  77
  Specificity of proteinase K from Tritirachium album for synthetic peptides
  Morihara, Kazuyuki; Tsuzuki, Hiroshige
  Agricultural and Biological Chemistry (1975), 39 (7), 1489-92CODEN: ABCHA6; ISSN:0002-1369.
  The specificity of proteinase K from T. Album Limber was detd. using various synthetic peptide substrates. The esterase activity against N-acylated amino acid esters indicated that the enzyme is primarily specific against aromatic or hydrophobic amino acid residues on the CO2H side of the cleavage point. The effect of neighboring amino acid residues on hydrolysis was also studied using peptide esters or other compds., which showed that the enzyme activity is markedly promoted by elongating the peptide chain on the N-terminal side of the cleavage point. Thus, peptide chloromethyl ketone derivatives such as Z-Ala-Gly-PheCH2Cl inactivated the enzyme activity markedly.
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78. 78
  Green, T. R.; Fisher, J.; Matthews, J. B.; Stone, M. H.; Ingham, E. Effect of Size and Dose on Bone Resorption Activity of Macrophages by in Vitro Clinically Relevant Ultra High Molecular Weight Polyethylene Particles. J. Biomed. Mater. Res. 2000, 53, 490– 497, DOI: 10.1002/1097-4636(200009)53:5<490::aid-jbm7>3.0.co;2-7
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79. 79
  Hayashi, Y.; Furue, M. K.; Okamoto, T.; Ohnuma, K.; Myoishi, Y.; Fukuhara, Y.; Abe, T.; Sato, J. D.; Hata, R.-I.; Asashima, M. Integrins Regulate Mouse Embryonic Stem Cell Self-Renewal. Stem Cells 2007, 25, 3005– 3015, DOI: 10.1634/stemcells.2007-0103
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  Saltó, C.; Saindon, E.; Bolin, M.; Kanciurzewska, A.; Fahlman, M.; Jager, E. W. H.; Tengvall, P.; Arenas, E.; Berggren, M. Control of Neural Stem Cell Adhesion and Density by an Electronic Polymer Surface Switch. Langmuir 2008, 24, 14133– 14138, DOI: 10.1021/la8028337
  80
  Control of Neural Stem Cell Adhesion and Density by an Electronic Polymer Surface Switch
  Salto, Carmen; Saindon, Emilien; Bolin, Maria; Kanciurzewska, Anna; Fahlman, Mats; Jager, Edwin W. H.; Tengvall, Pentti; Arenas, Ernest; Berggren, Magnus
  Langmuir (2008), 24 (24), 14133-14138CODEN: LANGD5; ISSN:0743-7463. (American Chemical Society)
  Adhesion is an essential parameter for stem cells. It regulates the overall cell d. along the carrying surface, which further dictates the differentiation scheme of stem cells toward a more matured and specified population as well as tissue. Electronic control of the seeding d. of neural stem cells (c17.2) is here reported. Thin electrode films of poly(3,4-ethylenedioxythiophene) (PEDOT):Tosylate were manufd. along the floor of cell growth dishes. As the oxidn. state of the conjugated polymer electrodes was controlled, the seeding d. could be varied by a factor of 2. Along the oxidized PEDOT:Tosylate-electrodes, a relatively lower d. of, and less tightly bonded, human serum albumin (HSA) was obsd. as compared to reduced electrodes. The authors found that this favors adhesion of the specific stem cells studied. Surface anal. expts., such as photoelectron spectroscopy, and water contact angle measurements, were carried out to investigate the mechanisms responsible for the electronic control of the seeding d. of the c17.2 neural stem cells. Further, the authors' findings may provide an opening for electronic control of stem cell differentiation.
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81. 81
  Li, N.; Zhang, Q.; Gao, S.; Song, Q.; Huang, R.; Wang, L.; Liu, L.; Dai, J.; Tang, M.; Cheng, G. Three-Dimensional Graphene Foam as a Biocompatible and Conductive Scaffold for Neural Stem Cells. Sci. Rep. 2013, 3, 1604, DOI: 10.1038/srep01604
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  Three-dimensional graphene foam as a biocompatible and conductive scaffold for neural stem cells
  Li, Ning; Zhang, Qi; Gao, Song; Song, Qin; Huang, Rong; Wang, Long; Liu, Liwei; Dai, Jianwu; Tang, Mingliang; Cheng, Guosheng
  Scientific Reports (2013), 3 (), 1604, 6 pp.CODEN: SRCEC3; ISSN:2045-2322. (Nature Publishing Group)
  Neural stem cell (NSC) based therapy provides a promising approach for neural regeneration. For the success of NSC clin. application, a scaffold is required to provide 3-dimensional (3D) cell growth microenvironments and appropriate synergistic cell guidance cues. Here, the authors report the first utilization of graphene foam, a 3D porous structure, as a novel scaffold for NSCs in vitro. It was found that 3-dimensional graphene foams (3D-GFs) can not only support NSC growth, but also keep cell at an active proliferation state with upregulation of Ki67 expression than that of 2-dimensional graphene films. Meanwhile, phenotypic anal. indicated that 3D-GFs can enhance the NSC differentiation towards astrocytes and esp. neurons. Furthermore, a good elec. coupling of 3D-GFs with differentiated NSCs for efficient elec. stimulation was obsd. The authors' findings implicate 3D-GFs could offer a powerful platform for NSC research, neural tissue engineering and neural prostheses.
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82. 82
  Snydman, D. R.; Walker, M.; Kublin, J. G.; Zunt, J. R. Parasitic Central Nervous System Infections in Immunocompromised Hosts: Malaria, Microsporidiosis, Leishmaniasis, and African Trypanosomiasis. Clin. Infect. Dis. 2006, 42, 115– 125, DOI: 10.1086/498510
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  Sanfeld, A.; Royer, C.; Steinchen, A. Thermodynamic, Kinetic and Conformational Analysis of Proteins Diffusion–sorption on a Solid Surface. Adv. Colloid Interface Sci. 2015, 222, 639– 660, DOI: 10.1016/j.cis.2014.10.006
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  Norde, W. Protein Adsorption at Solid Surfaces: A Thermodynamic Approach. Pure Appl. Chem. 1994, 66, 491, DOI: 10.1351/pac199466030491
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  Protein adsorption at solid surfaces: a thermodynamic approach
  Norde, Willem
  Pure and Applied Chemistry (1994), 66 (3), 491-6CODEN: PACHAS; ISSN:0033-4545.
  Protein adsorption data for human serum albumin, lysozyme, and α-lactalbumin on polystyrene are interpreted using thermodn. arguments. Energetic and entropic contributions from the major subprocesses that constitute the overall adsorption process are presented.
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85. 85
  Yeung, T.; Gilbert, G. E.; Shi, J.; Silvius, J.; Kapus, A.; Grinstein, S. Membrane Phosphatidylserine Regulates Surface Charge and Protein Localization. Science 2008, 319, 210– 213, DOI: 10.1126/science.1152066
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  Membrane Phosphatidylserine Regulates Surface Charge and Protein Localization
  Yeung, Tony; Gilbert, Gary E.; Shi, Jialan; Silvius, John; Kapus, Andras; Grinstein, Sergio
  Science (Washington, DC, United States) (2008), 319 (5860), 210-213CODEN: SCIEAS; ISSN:0036-8075. (American Association for the Advancement of Science)
  Electrostatic interactions with neg. charged membranes contribute to the subcellular targeting of proteins with polybasic clusters or cationic domains. Although the anionic phospholipid phosphatidylserine is comparatively abundant, its contribution to the surface charge of individual cellular membranes is unknown, partly because of the lack of reagents to analyze its distribution in intact cells. We developed a biosensor to study the subcellular distribution of phosphatidylserine and found that it binds the cytosolic leaflets of the plasma membrane, as well as endosomes and lysosomes. The neg. charge assocd. with the presence of phosphatidylserine directed proteins with moderately pos. charge to the endocytic pathway. More strongly cationic proteins, normally assocd. with the plasma membrane, relocalized to endocytic compartments when the plasma membrane surface charge decreased on calcium influx.
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86. 86
  White, G.; Lovinger, D. M.; Weight, F. F. Transient Low-Threshold Ca2+ Current Triggers Burst Firing through an Afterdepolarizing Potential in an Adult Mammalian Neuron. Proc. Natl. Acad. Sci. U.S.A. 1989, 86, 6802– 6806, DOI: 10.1073/pnas.86.17.6802
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87. 87
  Monteith, G. R.; McAndrew, D.; Faddy, H. M.; Roberts-Thomson, S. J. Calcium and Cancer: Targeting Ca2+ Transport. Nat. Rev. Cancer 2007, 7, 519– 530, DOI: 10.1038/nrc2171
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  Calcium and cancer: targeting Ca2+ transport
  Monteith, Gregory R.; McAndrew, Damara; Faddy, Helen M.; Roberts-Thomson, Sarah J.
  Nature Reviews Cancer (2007), 7 (7), 519-530CODEN: NRCAC4; ISSN:1474-175X. (Nature Publishing Group)
  A review. Ca2+ is a ubiquitous cellular signal. Altered expression of specific Ca2+ channels and pumps are characterizing features of some cancers. The ability of Ca2+ to regulate both cell death and proliferation, combined with the potential for pharmacol. modulation, offers the opportunity for a set of new drug targets in cancer. However, the ubiquity of the Ca2+ signal is often mistakenly presumed to thwart the specific therapeutic targeting of proteins that transport Ca2+. This review presents evidence to the contrary and addresses the question: which Ca2+ channels and pumps should be targeted.
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88. 88
  Isaksson, J.; Kjäll, P.; Nilsson, D.; Robinson, N.; Berggren, M.; Richter-Dahlfors, A. Electronic Control of Ca2+ Signalling in Neuronal Cells Using an Organic Electronic Ion Pump. Nat. Mater. 2007, 6, 673– 679, DOI: 10.1038/nmat1963
  88
  Electronic control of Ca2+ signaling in neuronal cells using an organic electronic ion pump
  Isaksson, Joakim; Kjaell, Peter; Nilsson, David; Robinson, Nathaniel; Berggren, Magnus; Richter-Dahlfors, Agneta
  Nature Materials (2007), 6 (9), 673-679CODEN: NMAACR; ISSN:1476-1122. (Nature Publishing Group)
  Cells and tissues use finely regulated ion fluxes for their intra- and intercellular communication. Technologies providing spatial and temporal control for studies of such fluxes are however, limited. We have developed an electrophoretic ion pump made of poly(3,4-ethylenedioxythiophene) doped with poly(styrene sulfonate) (PEDOT:PSS) to mediate electronic control of the ion homeostasis in neurons. Ion delivery from a source reservoir to a receiving electrolyte via a PEDOT:PSS thin-film channel was achieved by electronic addressing. Ions are delivered in high quantities at an assocd. on/off ratio exceeding 300. This induces physiol. signaling events that can be recorded at the single-cell level. Furthermore, miniaturization of the device to a 50-μm-wide channel allows for stimulation of individual cells. As this technol. platform allows for electronic control of ion signaling in individual cells with proper spatial and temporal resoln., it will be useful in further studies of communication in biol. systems.
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89. 89
  Taylor, A. C.; González, C. H.; Miller, B. S.; Edgington, R. J.; Ferretti, P.; Jackman, R. B. Surface Functionalisation of Nanodiamonds for Human Neural Stem Cell Adhesion and Proliferation. Sci. Rep. 2017, 7, 7307, DOI: 10.1038/s41598-017-07361-y
  89
  Surface functionalisation of nanodiamonds for human neural stem cell adhesion and proliferation
  Taylor Alice C; Miller Benjamin S; Edgington Robert J; Jackman Richard B; Gonzalez Citlali Helenes; Ferretti Patrizia
  Scientific reports (2017), 7 (1), 7307 ISSN:.
  Biological systems interact with nanostructured materials on a sub-cellular level. These interactions may govern cell behaviour and the precise control of a nanomaterial's structure and surface chemistry allow for a high degree of tunability to be achieved. Cells are surrounded by an extra-cellular matrix with nano-topographical properties. Diamond based materials, and specifically nanostructured diamond has attracted much attention due to its extreme electrical and mechanical properties, chemical inertness and biocompatibility. Here the interaction of nanodiamond monolayers with human Neural Stem Cells (hNSCs) has been investigated. The effect of altering surface functionalisation of nanodiamonds on hNSC adhesion and proliferation has shown that confluent cellular attachment occurs on oxygen terminated nanodiamonds (O-NDs), but not on hydrogen terminated nanodiamonds (H-NDs). Analysis of H and O-NDs by Atomic Force Microscopy, contact angle measurements and protein adsorption suggests that differences in topography, wettability, surface charge and protein adsorption of these surfaces may underlie the difference in cellular adhesion of hNSCs reported here.
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90. 90
  Gao, M.; Wang, Y.; Yi, Q.; Su, Y.; Sun, P.; Wang, X.; Zhao, J.; Zou, G. A Novel Solid-State Electrolyte Based on a Crown Ether Lithium Salt Complex. J. Mater. Chem. A 2015, 3, 20541– 20546, DOI: 10.1039/c5ta04933d
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  A novel solid-state electrolyte based on a crown ether lithium salt complex
  Gao, Minda; Wang, Yun; Yi, Qinghua; Su, Ying; Sun, Pengfei; Wang, Xiangguo; Zhao, Jie; Zou, Guifu
  Journal of Materials Chemistry A: Materials for Energy and Sustainability (2015), 3 (41), 20541-20546CODEN: JMCAET; ISSN:2050-7496. (Royal Society of Chemistry)
  A novel crown ether lithium salt complex [Li∈12-C-4][I] has been designed, synthesized and characterized. The thermal properties of the [Li∈12-C-4][I] based solid-state electrolytes were also investigated in detail. The particular trapping ability of 12-crown-4 to Li+ can obviously reduce the cation-anion (Li+-I-) interaction and hence facilitate favorable elec. properties of the solid-state electrolytes. Therefore, [Li∈12-C-4][I] represents ionic cond. of 3.93 × 10-5 and 1.53 × 10-4 S cm-1 at 25 and 80 °C, resp. Further addn. of the ionic liq. 1-propyl-3-methylimidazolium iodine as a crystal growth inhibitor can effectively suppress the crystn. of the complex for more amorphous and smoother regions, which are much more conducive towards higher ion cond. by the segmental motion of mol. chains. For application, the resulting device showed a power conversion efficiency of 5% and displayed excellent long-term stability. These results offer us more opportunities to explore simple and novel solid-state electrolytes for energy storage and conversion.
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91. 91
  Neese, F. The ORCA Program System. Wiley Interdiscip. Rev.: Comput. Mol. Sci. 2012, 2, 73– 78, DOI: 10.1002/wcms.81
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  The ORCA program system
  Neese, Frank
  Wiley Interdisciplinary Reviews: Computational Molecular Science (2012), 2 (1), 73-78CODEN: WIRCAH; ISSN:1759-0884. (Wiley-Blackwell)
  A review. ORCA is a general-purpose quantum chem. program package that features virtually all modern electronic structure methods (d. functional theory, many-body perturbation and coupled cluster theories, and multireference and semiempirical methods). It is designed with the aim of generality, extendibility, efficiency, and user friendliness. Its main field of application is larger mols., transition metal complexes, and their spectroscopic properties. ORCA uses std. Gaussian basis functions and is fully parallelized. The article provides an overview of its current possibilities and documents its efficiency.
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92. 92
  Perdew, J. P.; Burke, K.; Ernzerhof, M. Generalized Gradient Approximation Made Simple. Phys. Rev. Lett. 1996, 77, 3865– 3868, DOI: 10.1103/physrevlett.77.3865
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  Generalized gradient approximation made simple
  Perdew, John P.; Burke, Kieron; Ernzerhof, Matthias
  Physical Review Letters (1996), 77 (18), 3865-3868CODEN: PRLTAO; ISSN:0031-9007. (American Physical Society)
  Generalized gradient approxns. (GGA's) for the exchange-correlation energy improve upon the local spin d. (LSD) description of atoms, mols., and solids. We present a simple derivation of a simple GGA, in which all parameters (other than those in LSD) are fundamental consts. Only general features of the detailed construction underlying the Perdew-Wang 1991 (PW91) GGA are invoked. Improvements over PW91 include an accurate description of the linear response of the uniform electron gas, correct behavior under uniform scaling, and a smoother potential.
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93. 93
  Schäfer, A.; Horn, H.; Ahlrichs, R. Fully Optimized Contracted Gaussian Basis Sets for Atoms Li to Kr. J. Chem. Phys. 1992, 97, 2571, DOI: 10.1063/1.463096
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94. 94
  Weigend, F.; Ahlrichs, R. Balanced Basis Sets of Split Valence, Triple Zeta Valence and Quadruple Zeta Valence Quality for H to Rn: Design and Assessment of Accuracy. Phys. Chem. Chem. Phys. 2005, 7, 3297– 3305, DOI: 10.1039/b508541a
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  Balanced basis sets of split valence, triple zeta valence and quadruple zeta valence quality for H to Rn: Design and assessment of accuracy
  Weigend, Florian; Ahlrichs, Reinhart
  Physical Chemistry Chemical Physics (2005), 7 (18), 3297-3305CODEN: PPCPFQ; ISSN:1463-9076. (Royal Society of Chemistry)
  Gaussian basis sets of quadruple zeta valence quality for Rb-Rn are presented, as well as bases of split valence and triple zeta valence quality for H-Rn. The latter were obtained by (partly) modifying bases developed previously. A large set of more than 300 mols. representing (nearly) all elements-except lanthanides-in their common oxidn. states was used to assess the quality of the bases all across the periodic table. Quantities investigated were atomization energies, dipole moments and structure parameters for Hartree-Fock, d. functional theory and correlated methods, for which we had chosen Moller-Plesset perturbation theory as an example. Finally recommendations are given which type of basis set is used best for a certain level of theory and a desired quality of results.
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95. 95
  Grimme, S.; Ehrlich, S.; Goerigk, L. Effect of the Damping Function in Dispersion Corrected Density Functional Theory. J. Comput. Chem. 2011, 32, 1456– 1465, DOI: 10.1002/jcc.21759
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  Effect of the damping function in dispersion corrected density functional theory
  Grimme, Stefan; Ehrlich, Stephan; Goerigk, Lars
  Journal of Computational Chemistry (2011), 32 (7), 1456-1465CODEN: JCCHDD; ISSN:0192-8651. (John Wiley & Sons, Inc.)
  It is shown by an extensive benchmark on mol. energy data that the math. form of the damping function in DFT-D methods has only a minor impact on the quality of the results. For 12 different functionals, a std. "zero-damping" formula and rational damping to finite values for small interat. distances according to Becke and Johnson (BJ-damping) has been tested. The same (DFT-D3) scheme for the computation of the dispersion coeffs. is used. The BJ-damping requires one fit parameter more for each functional (three instead of two) but has the advantage of avoiding repulsive interat. forces at shorter distances. With BJ-damping better results for nonbonded distances and more clear effects of intramol. dispersion in four representative mol. structures are found. For the noncovalently-bonded structures in the S22 set, both schemes lead to very similar intermol. distances. For noncovalent interaction energies BJ-damping performs slightly better but both variants can be recommended in general. The exception to this is Hartree-Fock that can be recommended only in the BJ-variant and which is then close to the accuracy of cor. GGAs for non-covalent interactions. According to the thermodn. benchmarks BJ-damping is more accurate esp. for medium-range electron correlation problems and only small and practically insignificant double-counting effects are obsd. It seems to provide a phys. correct short-range behavior of correlation/dispersion even with unmodified std. functionals. In any case, the differences between the two methods are much smaller than the overall dispersion effect and often also smaller than the influence of the underlying d. functional. © 2011 Wiley Periodicals, Inc.; J. Comput. Chem., 2011.
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Supporting Information
Supporting Information
The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acsomega.8b00510.
- ¹H NMR spectra, infrared spectra, j/E potentiodynamic profiles with all five cycles, and Nyquist plots of impedance spectroscopy for PEDOT-co-PDLLA 1:05, 1:25, and 1:50, respectively (PDF)
- ao8b00510_si_001.pdf (439.95 kb)
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Novel Conducting and Biodegradable Copolymers with Noncytotoxic Properties toward Embryonic Stem CellsClick to copy article linkArticle link copied!

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Abstract

Introduction

Results and Discussion

Synthesis of Conducting and Biodegradable Copolymer of PEDOT-co-PDLLA

Scheme 1

Figure 1

Electrochemical Behavior

Figure 2

Biodegradability Tests

Scheme 2

Figure 3

Water Contact Angle of PEDOT-co-PDLLA Films

Cytotoxicity

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Discussion

Conclusions

Experimental Section

Materials

Chemical Synthesis of Conducting and Biodegradable Copolymers PEDOT-co-PDLLA

Instrumentation

In Silico Structure Optimization

Cell Culture and Differentiation

Cell Viability Assay

Embryoid Body Attachment and Cell Migration Assay

Immunofluorescence Staining Assay

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Novel Conducting and Biodegradable Copolymers with Noncytotoxic Properties toward Embryonic Stem Cells
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