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Biological and Medical Applications of Materials and Interfaces

Hybrid Silver(I)-Doped Soybean Oil and Potato Starch Biopolymer Films to Combat Bacterial Biofilms
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  • Tiago A. Fernandes
    Tiago A. Fernandes
    Centro de Química Estrutural, Institute of Molecular Sciences, Departamento de Engenharia Química, Instituto Superior Técnico, Universidade de Lisboa, Av. Rovisco Pais, 1049-001 Lisbon, Portugal
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  • Inês F.M. Costa
    Inês F.M. Costa
    Centro de Química Estrutural, Institute of Molecular Sciences, Departamento de Engenharia Química, Instituto Superior Técnico, Universidade de Lisboa, Av. Rovisco Pais, 1049-001 Lisbon, Portugal
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  • Paula Jorge
    Paula Jorge
    Centre of Biological Engineering, University of Minho, Campus de Gualtar, 4710-057 Braga, Portugal
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  • Ana Catarina Sousa
    Ana Catarina Sousa
    Centro de Química Estrutural, Institute of Molecular Sciences, Departamento de Engenharia Química, Instituto Superior Técnico, Universidade de Lisboa, Av. Rovisco Pais, 1049-001 Lisbon, Portugal
    Área Departamental de Engenharia Química, ISEL─Instituto Superior de Engenharia de Lisboa, Instituto Politécnico de Lisboa, R. Conselheiro Emídio Navarro, 1, 1959-007 Lisbon, Portugal
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  • Vânia André
    Vânia André
    Centro de Química Estrutural, Institute of Molecular Sciences, Departamento de Engenharia Química, Instituto Superior Técnico, Universidade de Lisboa, Av. Rovisco Pais, 1049-001 Lisbon, Portugal
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    Orcidhttps://orcid.org/0000-0001-5599-8355
  • Rafaela G. Cabral
    Rafaela G. Cabral
    Centro de Química Estrutural, Institute of Molecular Sciences, Departamento de Engenharia Química, Instituto Superior Técnico, Universidade de Lisboa, Av. Rovisco Pais, 1049-001 Lisbon, Portugal
    Área Departamental de Engenharia Química, ISEL─Instituto Superior de Engenharia de Lisboa, Instituto Politécnico de Lisboa, R. Conselheiro Emídio Navarro, 1, 1959-007 Lisbon, Portugal
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  • Nuno Cerca*
    Nuno Cerca
    Centre of Biological Engineering, University of Minho, Campus de Gualtar, 4710-057 Braga, Portugal
    *Email: [email protected]
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  • Alexander M. Kirillov*
    Alexander M. Kirillov
    Centro de Química Estrutural, Institute of Molecular Sciences, Departamento de Engenharia Química, Instituto Superior Técnico, Universidade de Lisboa, Av. Rovisco Pais, 1049-001 Lisbon, Portugal
    *Email: [email protected]
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    Orcidhttps://orcid.org/0000-0002-2052-5280
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ACS Applied Materials & Interfaces

Cite this: ACS Appl. Mater. Interfaces 2022, 14, 22, 25104–25114
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https://doi.org/10.1021/acsami.2c03010
Published May 27, 2022

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Abstract

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This study describes the preparation, characterization, and antimicrobial properties of novel hybrid biopolymer materials doped with bioactive silver(I) coordination polymers (bioCPs). Two new bioCPs, [Ag2(μ6-hfa)]n (1) and [Ag2(μ4-nda)(H2O)2]n (2), were assembled from Ag2O and homophthalic (H2hfa) or 2,6-naphthalenedicarboxylic (H2nda) acids as unexplored building blocks. Their structures feature 2D metal–organic and supramolecular networks with 3,6L64 or sql topology. Both compounds act as active antimicrobial agents for producing bioCP-doped biopolymer films based on epoxidized soybean oil acrylate (SBO) or potato starch (PS) as model biopolymer materials with a different rate of degradability and silver release. BioCPs and their hybrid biopolymer films (1@[SBO]n, 2@[SBO]n, 1@[PS]n, and 2@[PS]n) with a very low loading of coordination polymer (0.05–0.5 wt %) show remarkable antimicrobial activity against Staphylococcus aureus and Staphylococcus epidermidis (Gram-positive) and Escherichia coli and Pseudomonas aeruginosa (Gram-negative) bacteria. Biopolymer films also effectively impair the formation of bacterial biofilms, allowing total biofilm inhibition in several cases. By reporting on new bioCPs and biopolymer films obtained from renewable biofeedstocks (soybean oil and PS), this study blends highly important research directions and widens a limited antimicrobial application of bioCPs and derived functional materials. This research thus opens up the perspectives for designing hybrid biopolymer films with outstanding bioactivity against bacterial biofilms.

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Introduction

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Bacterial biofilms represent a community of bacteria usually associated with a surface and encased within an extracellular matrix. Biofilms correspond to a very typical form for the growth of bacteria, which are naturally assembled on diverse interface types of materials and environments, including living organisms. (1) During the formation of biofilms, the adhesion of bacterial cells to the surface occurs with a simultaneous synthesis of a protective matrix. (2,3) This process enables bacteria to survive under aggressive environments (i.e., heat and treatment with antiseptics and antibiotics) and develop increased resistance, which nowadays constitutes a critical issue in human healthcare. (4−6) In fact, biofilms are largely responsible for persistent and chronic infection diseases in humans, which are often related with the use of biomaterials (e.g., implants, catheters, and valves). (7,8) Hence, the prevention of bacterial attachment to surfaces represents one of the most promising strategies to tackle biofilm formation and growth, namely, by investigating alternative functional materials, (9−11) capable of reducing bacterial adhesion and biofilm formation.
In this regard, bioCPs (bioactive coordination polymers) and bioMOFs (bioactive metal–organic frameworks) attracted a great deal of attention as promising antibacterial agents (12−21) composed of biocidal metal centers as well as linkers and/or guest species with antimicrobial activity. Among various metals with a potential antibacterial activity, silver is particularly appealing with the most significant bioactivity in addition to a relatively low intrinsic toxicity to human cells. (22−32)
Silver ions, nanoparticles, and coordination compounds are thus well recognized for their bactericidal activity with many partially implicit types of action mechanisms. (27,33−35) The examples include intrusion of Ag+ species into intracellular protein moieties and membranes of bacteria, particularly sulfur-containing proteins and phosphorus-containing deoxyribonucleic acid. Such interactions involving thiol functionalities in essential enzymes contribute to their deactivation, inhibit division of cells, and cause death of cells. (36−38) Prior results indicate that in bacteria subjected to treatment by Ag+ species, DNA can lose the ability to replicate, causing changes in the structures of cell membranes and in the development of minor electron-rich granules incorporating Ag and S elements. (36,38,39)
In pursuit of this discussion and high current perspectives of bioactive coordination polymers and derived materials, the principal aim of this work focused on the synthesis of new silver(I) bioCPs and assessment of their antimicrobial activity after incorporation as antimicrobial dopants into biopolymer films. This research direction tracks a trend for the design of renewable and biodegradable biopolymer materials with diverse applications. (40−43) As an example, the search for alternative biodegradable packaging products has seen a great development in response to the biological incompatibility of non-biodegradable packaging materials. Biopolymer films that simultaneously comprise an antimicrobial component and derive from the natural bio-based precursors [e.g., soybean oil and potato starch (PS)] may find a high significance in this field.
Specifically, epoxidized soybean oil acrylate (SBO) and PS are considered very promising candidates as organic polymer matrices for the production of antimicrobial biomaterials. Soy protein isolate (SPI) is a promising packaging material derived from the edible oil industry and possesses advantages such as biocompatibility, biodegradability, and film-forming capacity. The limited practical applications of SPI-based films have led to an increased research on epoxide compounds that are able to enhance their mechanical properties. In this regard, SBO represents a particularly interesting substrate for the preparation of biopolymers. (44−46)
Apart from SBO, PS can also act as a low-cost biodegradable polymer matrix to immobilize antimicrobial bioCPs. As a polysaccharide widely used to produce green biomaterials, starch constitutes a renewable and sustainable polymer and represents one of the most commercially available biofeedstocks. (47) The non-biodegradability of petrochemical-based materials generated a strong demand for “green alternatives”, such as starch-based biodegradable bioplastics. Thus, PS is considered as a highly attractive resource for the production of biopolymer films in the packaging industry. (48−51)
Aiming at fabricating novel functional materials and merging both the synthetic and antimicrobial approaches, the current work reports on the synthesis of new silver(I) bioactive coordination polymers as well as their application as dopants for the preparation of hybrid bioCP-doped biopolymer films based on [SBO]n or [PS]n. Hence, two new bioCPs, [Ag2(μ6-hfa)]n (1) and [Ag2(μ4-nda)(H2O)2]n (2), were assembled from homophthalic (H2hfa) or 2,6-naphthalenedicarboxylic (H2nda) acids as linkers and applied in the production of hybrid biopolymer film materials. These were then screened for their potential to prevent the growth of bacteria and biofilms. By reporting on new bioCPs along with hybrid biopolymer films and their antibacterial and biofilm inhibition properties, this multidisciplinary study not only blends different highly important research directions but also widens a still limited antimicrobial application of coordination polymers and derived biomaterials.

Results and Discussion

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Preparation of bioCPs

New silver(I) bioCPs formulated as [Ag2(μ6-hfa)]n (1) and [Ag2(μ4-nda)(H2O)2]n (2) were self-assembled from an acetonitrile–methanol reaction mixture composed of silver(I) oxide, homophthalic (H2hfa) or 2,6-naphthalenedicarboxylic (H2nda) acid, 2-dimethylaminoethanol (template), and aqueous ammonium hydroxide (Figure S1, Supporting Information). Both products 1 and 2 were isolated as air-stable crystalline compounds having a mean size of particles of 66 and 51 μm, respectively (Figures S2 and S6). The formulation and structures of the obtained compounds were confirmed by C/H/N analyses, IR (Figures S7 and S8) and NMR spectroscopies, and X-ray diffraction methods (SCXD and PXRD, Figures S20 and S21).

Preparation of Hybrid BioCP-Doped Biopolymer Films

Two types of hybrid biopolymer films were fabricated by dispersing very low amounts of bioCPs in the biopolymer precursors based on the epoxidized SBO, or PS with glycerol, followed by polymerization in Petri dishes (Figures 1 and S4). The examples of sample coupons for [SBO]n and [PS]n biopolymer films that were cut and used for antimicrobial studies are shown in Figure 2. Low loadings (0.05, 0.01, and 0.5 wt %) of bioCPs were explored, giving origin to the biopolymer thin films (∼1 mm thickness) abbreviated as 1-0.5%@[SBO]n, 1-0.1%@[SBO]n, and 1-0.05%@[SBO]n; 2-0.5%@[SBO]n, 2-0.1%@[SBO]n, and 2-0.05%@[SBO]n (SBO series); as well as 1-0.5%@[PS]n and 2-0.5%@[PS]n (PS series) (Figure S5). For comparison, the negative control ([SBO]n and [PS]n) as well as the positive control (Ag2O-0.05%@[SBO]n, Ag2O-0.1%@[SBO]n, Ag2O-0.5%@[SBO]n, and Ag2O-0.5%@[PS]n) biopolymer films were also fabricated. The obtained materials were characterized by ATR-FTIR (Figures S9–S14) and SEM–EDX (Figures 5, S15, and S16). The latter revealed a generally uniform distribution of bioCPs, although these may occasionally be concentrated in areas containing larger crystalline particles. Water absorption and stability of films in PBS medium were also evaluated in addition to silver ion release experiments (Table S1 and Figures S17 and S18). In fact, both types of biopolymer films show a gradual disaggregation (limited stability) along time in PBS medium (Figure S17, Supporting Information) and feature a minor release of Ag+ ions after 24 h, namely, 10–20 and 49–57 μg/L, for [SBO]n and [PS]n films doped by 0.5% bioCPs, respectively. We would like to emphasize that the materials should not be intact to show antimicrobial performance.

Figure 1

Figure 1. Preparation of bioCP-doped [SBO]n and [PS]n biopolymer films.

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Figure 2

Figure 2. Sample coupons for (a) [SBO]n and (b) [PS]n biopolymer films.

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Similar to a majority of related CPs or MOFs, both the obtained bioCPs are marginally soluble in H2O and in reaction medium during the film formation. This makes more difficult the homogeneous distribution of coordination polymers within the biopolymer films. However, in contrast to discrete soluble complexes or silver salts, the release of silver ions from bioCP-based films is significantly slower, which represents an advantage of these materials in terms of relative stability and possible long-term use. Both carboxylic acid ligands in 1 and 2 were chosen given their unexplored use as building blocks for assembling bioCPs and due to their different hydrolipophilic properties, for example, log P = 1.18 for homophthalic acid and log P = 2.80 for 2,6-naphthalenedicarboxylic acid. However, when these ligands are coordinated to silver, they form almost insoluble bioCPs, with a different rate of silver ion release.

Structural Description of bioCPs 1 and 2

The structure of [Ag2(μ6-hfa)]n (1) discloses an intricate 2D metal–organic double layer (Figure 3), which is constructed from two structurally distinct Ag1/Ag2 centers and a μ6-homophthalate2– linker (Figure 3a,b). This linker simultaneously binds to three Ag1 and three Ag2 atoms by carboxylate groups that act in the μ3-bridging tridentate and μ4-bridging tetradentate modes. The Ag1 center is 3-coordinate featuring a distorted trigonal planar arrangement of three carboxylate O donor atoms with the Ag1–O distances in the 2.1677(1)–2.4711(1) Å range. The Ag2 center is 4-coordinate by four oxygen atoms coming from three μ6-hfa2– blocks with the Ag2–O bonds varying in the 2.2193(1)–2.6405(1) Å interval. In addition, both the Ag1 and Ag2 centers participate in several weak argentophilic interactions, wherein the Ag···Ag distances are in the 2.8204(6)–3.1861(5) Å interval (Figure 3b). These interactions reinforce the 2D metal–organic network (Figure 3c,d) that is driven by the μ6-hfa2– linkers and features a 3,6L64 topology (Figure S3a,b). Despite being rather simple and commercially available, homophthalic acid has not yet been applied for designing silver complexes and CPs as evidenced by CSD search. Hence, bioCP 1 represents a unique example of Ag(I) coordination polymer derived from H2hfa.

Figure 3

Figure 3. Structural fragments of [Ag2(μ6-hfa)]n (1). (a) Coordination mode of μ6-hfa2– ligand. (b) Coordination environment of silver atoms including argentophilic interactions (dotted cyan lines). (c,d) Front (c) and side (d) view of 2D double layer. Further details: (a–d) Ag (cyan), C (gray), and O (red); views along the c (c) and a (d) axes.

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The structure of [Ag2(μ4-nda)(H2O)2]n (2) is assembled from the symmetry equivalent Ag1 atoms, μ4-nda2– spacers, and terminal water ligands (Figure 4). Note that the discussion is based on the major occupancy Ag atom (Ag1), but similar conclusions can be drawn for the Ag2 center. The Ag1 atoms are surrounded by three oxygen atoms, two coming from the μ4-nda2– blocks and one from the H2O ligand with the Ag1–O bonds ranging from 2.1203(3)(3) to 2.7146(4) Å (Figure 4a,b). There are also weaker Ag···Ag [3.01–3.25 Å] and Ag···O [3.26 Å] interactions which, along with the μ4-nda2– linkers, result in the assembly of a two-dimensional supramolecular net (Figure 4b) with an sql topology (Figure S3c). The compound 2 widens the types of CPs constructed from the nda2– linkers. (52,53)

Figure 4

Figure 4. Structural fragments of [Ag2(μ4-nda)(H2O)2]n (2). (a) Coordination mode of μ4-nda2– ligand and environment of Ag1 centers; weaker argentophilic Ag···Ag and Ag···O interactions are shown as dotted lines. (b) 2D supramolecular layer. Further details: Ag (cyan), C (gray), and O (red); (b) view along the c axis.

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Morphological Characterization of bioCP-Doped Biopolymer Films

The bioCP-doped [SBO]n and [PS]n biopolymer films were examined by SEM–EDX (Figure 5) to further evaluate their morphology and incorporation of bioCPs 1 or 2 into the films. As observed in Figure 5b,e, coordination polymers 1 and 2 were directly embedded within the [SBO]n matrix, also being present at the surface of the films (Figure 5b). The material was then evaluated by SEM–EDX using a silver analysis probe for determining Ag distribution (Figure 5c,e). From the Ag overlay on the SEM image of the 2-0.5%@[SBO]n film (Figure 5e), it can be seen that silver is well distributed and only occasionally concentrated in areas containing larger crystalline particles of bioCP 2. The oxygen distribution does not provide additional details because O element is present in both the polymer matrix and bioCPs (Figure 5f). Figure 5g shows a morphological characterization of the [PS]n film. Figure 5h,i shows the same region of 1-0.5%@[PS]n, where bioCP particles can be seen throughout the material, which is evidenced by EDX analysis of Ag distribution. In general, the films are quite uniform (Figure 5c,e,i), although it is possible to occasionally observe areas containing increased bioCP concentrations (Figures S15 and S16, Supporting Information). However, taking into account the sample coupon as a whole, any eventual deviation in the distribution of bioCPs is irrelevant, as confirmed by the reproducibility of biological assays that were made in triplicate.

Figure 5

Figure 5. Morphological characterization of [SBO]n and [PS]n films by SEM–EDX. SEM images: (a) SBO film; (b) 1-0.5%@[SBO]n; (c) 1-0.5%@[SBO]n [the same region as (b)] with EDX analysis of Ag distribution; (d) 2-0.5%@[SBO]n, where bioCP particles can be seen throughout the material; (e) 2-0.5%@[SBO]n with EDX analysis of Ag distribution; (f) 2-0.5%@[SBO]n (the same region as e) with EDX analysis of O distribution; (g) [PS]n film; (h) 1-0.5%@[PS]n, where bioCP particles can be seen throughout the material; (i) 1-0.5%@[PS]n (the same region as h) with EDX analysis of Ag distribution. Images (a), (d), (i), and (h) were obtained at 1000× magnification and (b,c,e,f,i) at 500× magnification.

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Thermogravimetric Analysis

The thermal stability of bioCP-doped and undoped [SBO]n and [PS]n biopolymer films was investigated by TGA under nitrogen flow (Figure S19, Supporting Information). All [SBO]n-based samples display similar patterns with one major degradation stage between 300 and 470 °C, corresponding to a 90% weight loss. For [PS]n-based samples, there are several thermal effects with major mass losses in the 50–250 and 250–350 °C intervals, eventually corresponding to a release of absorbed H2O/glycerol and the decomposition of biopolymers, respectively. (54,55) The third step of weight loss (350–700 °C) can be assigned to final carbonization. Other difference in the TGA patterns observed between the bioCP-doped samples and sole [PS]n might be regarded to a different content of absorbed water and glycerol present in these samples.

Antibacterial Activity

The obtained bioCPs exhibited antibacterial behavior against all tested species (Figure 6). In terms of susceptibility, the following rough trend was observed: Escherichia coli < Staphylococcus aureus < Pseudomonas aeruginosa < Staphylococcus epidermidis. No link of antibacterial efficiency with Gram classification was observed. Compound 1 had higher antibacterial action against P. aeruginosa and S. epidermidis in comparison with 2, which can be evidenced by larger radii of inhibition. For S. aureus, the antibacterial activities of 1 and 2 were comparable (Figure 6). In turn, compound 2 was more effective against E. coli.

Figure 6

Figure 6. (a) Minimum inhibition radius (mean ± SD) showing the normalized activity of 1 and 2 against P. aeruginosa and E. coli (Gram-negative) and S. aureus and S. epidermidis (Gram-positive) bacteria. (b) Examples of the obtained halos representing bacterial growth inhibition.

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Concerning the antibacterial activity of the Ag-doped [SBO]n films, 2@[SBO]n stood out as the most effective against all four bacterial strains, with a concentration-dependent efficacy (Figure 7). This is different from the above-discussed data for free compounds, wherein bioCP 1 revealed a superior efficiency (except for E. coli). This difference might be regarded to distinct diffusion patterns of silver compounds in the [SBO]n film. In fact, a higher Ag+ release rate of 20 μg·L–1 was observed for 2@[SBO]n versus 1@[SBO]n after 24 h in PBS (Figure S18).

Figure 7

Figure 7. Normalized activity of [SBO]n biopolymer films containing varying concentrations of Ag2O (Ag2O@[SBO]n) and compounds 1 (1@[SBO]n) and 2 (2@[SBO]n) against P. aeruginosa and E. coli (Gram-negative) and S. aureus and S. epidermidis (Gram-positive) bacteria.

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Both 1@[SBO]n and Ag2O@[SBO]n had little activity in comparison with 2@[SBO]n. All the three films had similar ineffectiveness at 0.05 wt % loading. The least susceptible bacteria to 2@[SBO]n was E. coli, while S. epidermidis was the most susceptible.
To compare an antimicrobial efficiency of silver(I) compounds in [SBO]n versus [PS]n films, an antibacterial assay was performed for both biopolymers encompassing the most effective concentration of bioCPs (0.5%). The antimicrobial activity of compound 1 was substantially higher when loaded into [PS]n rather than [SBO]n films. Similarly, Ag2O also showed some increased activity in [PS]n films. In turn, compound 2 had a resembling antimicrobial activity in both films (Figure 8). The differences encountered between the two films are related with their composition, namely, a higher water content in [PS]n versus residual water in [SBO]n, as observed by FTIR (Figures S9 and S12), which may lead to a quicker solubilization and/or migration of bioCPs from [PS]n. In fact, this was further confirmed by a faster Ag+ release to the media from both 1-0.5%@[PS]n and 2-0.5%@[PS]n samples if compared with Ag-doped [SBO]n samples (Figure S18).

Figure 8

Figure 8. Normalized activity of [SBO]nvs [PS]n biopolymer films containing 0.5% of Ag2O and compounds 1 and 2 against P. aeruginosa and E. coli (Gram-negative) and S. aureus and S. epidermidis (Gram-positive) bacteria. Significant statistical differences were found using the two-way ANOVA and subsequent Bonferroni’s multiple comparisons test with 95% confidence interval, represented as *P ≤ 0.05; **P ≤ 0.01; and ***P ≤ 0.001.

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The increase in mass as a percentage of dry mass for both types of biopolymer films was studied to determine water absorption. All samples were kept in water solution for 24 h. Based on the results (Table S1), it is clear that water absorption of 60% is higher for [PS]n films in comparison to a residual 1% absorption of [SBO]n films. As expected, higher water absorption well correlates with an affinity of [PS]n films to water as discussed above. All these findings well rationalize an observed bioactivity of different biopolymer films.
The amount of silver ions released, from both materials (with 0.5% concentration of bioCP, 1-0.5%@[SBO]n, and 1-0.5%@[PS]n), to PBS solution was determined by ICP-OES. In addition to proving a stability of materials, it revealed that only 0.06% of all silver present in the sample was released after 24 h from 1@[SBO]n, in contrast to 0.36% for 1@[PS]n, which corresponds to 10 and 57 μg·L–1, respectively. Similar results were obtained for 2@[SBO]n and 2@[PS]n, showing that [PS]n films release 6 times more silver ions to the aqueous medium within 24 h (Figures S17 and S18). The different Ag+ release rates observed for bioCP-doped [SBO]n and [PS]n biopolymer films are associated with the intrinsic properties (permeability, stability, degradability, and water absorption) of the biopolymer films. An effect of eventual interaction of compounds 1 and 2 with [SBO]n and [PS]n on release rate of Ag+ is negligible, given also a very low content (only 0.05–0.5%) of these bioCPs used as dopants.
A number of Ag(I) coordination polymers or metal–organic frameworks with various Ag–O, Ag–N, and/or Ag–P coordination environment types have been documented as antimicrobial compounds, with significant activity against the types of bacteria tested in the present study (Table S2, Supporting Information). (18,19,21,56−58) Given the difference in the content of antimicrobial components and the use of distinct assays for evaluation of bioactivity, a quantitative comparison of the observed activities is not feasible. Besides, the normalized antimicrobial activity of biopolymer films doped with bioCPs is generally comparable or even superior than that shown by the reference films doped with Ag2O and AgNO3 (Table S3, Supporting Information). Especially, the 2-0.1%@[SBO]n films exhibit a higher activity for all the tested types of bacteria if compared to the respective AgNO3-0.1%@[SBO]n films. Hence, important advantages of the bioCPs and materials reported in the present work concern (1) a usage of inexpensive soybean oil and PS as precursors for biopolymers, (2) a pronounced antimicrobial activity of the obtained films despite a very low loading of bioCPs (0.05–0.5%), (3) a simple generation of compounds 1 and 2 from commercially available reagents, and (4) a possibility of applying the biopolymer films to inhibit the growth of bacterial biofilms.

Biofilm Inhibition Activity

The Ag-doped [SBO]n films were also tested for their ability to prevent biofilm formation. Similar to its antibacterial activity, 2@[SBO]n was overall the most effective in partially preventing all the four bacterial species from forming biofilms on its surface (Figure 9). The Gram-positive bacteria, S. epidermidis and S. aureus, seem to be the most susceptible to 2@[SBO]n, with reductions above 3 log (99.9% bacterial growth reduction). The effect of 1@[SBO]n was much lower, with some effect (although lower than 1 log reduction, i.e., <90%) at the highest concentration against P. aeruginosa and E. coli (Gram-negative) bacteria, while the activity of Ag2O@[SBO]n as a positive control was virtually non-existent.

Figure 9

Figure 9. Normalized biofilm inhibition activity of [SBO]n biopolymer films containing varying concentration of Ag2O (Ag2O@[SBO]n) and compounds 1 (1@[SBO]n) and 2 (2@[SBO]n), against P. aeruginosa and E. coli (Gram-negative) and S. aureus and S. epidermidis (Gram-positive) bacteria. Significant statistical differences were found using the two-way ANOVA and subsequent Bonferroni’s multiple comparisons test with 95% confidence interval, represented as *P ≤ 0.05; **P ≤ 0.01; and ***P ≤ 0.001.

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In parallel with what was observed for the antibacterial activity, the efficacy of the bioCP-doped [SBO]n films in preventing biofilm formation was compared with that of the respective [PS]n films. Overall, the efficacy of Ag2O and compound 2 was similar for both films, while the efficacy of compound 1 was much higher in [PS]n films (Figure 10). This correlates with what was observed for the antibacterial activity (Figure 8) and silver release tests (Figure S18).

Figure 10

Figure 10. Normalized biofilm inhibition activity of [SBO]nvs [PS]n biopolymer films doped with 0.5% of Ag2O and compounds 1 and 2 against P. aeruginosa and E. coli (Gram-negative) and S. aureus and S. epidermidis (Gram-positive) bacteria. Significant statistical differences were found using the two-way ANOVA and subsequent Bonferroni’s multiple comparisons test with 95% confidence interval, represented as *P ≤ 0.05; **P ≤ 0.01; and ***P ≤ 0.001.

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Experimental Section

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Self-Assembly Synthesis and Characterization of 1 and 2

[Ag2(μ6-hfa)]n (1)

Acetonitrile (7 mL) and methanol (3 mL) were added to Ag2O (0.232 g, 1 mmol). Then, homophthalic acid (H2hfa, 0.180 g, 1 mmol), 2-dimethylaminoethanol (Hdmea, 1.0 mmol, 0.1 mL), and 8.0 mL of aq NH4OH (33%) were added, and the reaction mixture was stirred for 30 min at room temperature, followed by filtration (filter paper). An obtained filtrate was slowly evaporated in a vial in air. Colorless microcrystals (including suitable for X-ray diffraction) appeared in 1–2 weeks, which were separated and air-dried to afford bioCP 1 in 59% yield relatively to silver(I) oxide. BioCP 1 is barely soluble in water (0.065 mg·mL–1). Analysis calculated (%) for 1, C9H6Ag2O4 + 0.5CH3OH + 0.25CH3CN (1 + 0.5CH3OH + 0.25CH3CN): C, 28.59; H, 2.10; N, 0.83. Found: C, 29.04; H, 1.63; N, 0.47. FTIR-ATR (cm–1): 3207 m ν(H2O), 3065 m ν(H2O), 1606 m, 1583 m, 1539 m νas(COO), 1423 s, 1309 s νs(COO), 1145 w, 1041 w, 920 w, 827 w, 747 m, 716 s, 668 s cm–1. 1H NMR (DMSO-d6, 400 MHz): δ ppm 7.59 (1H, d, J = 7.1 Hz), 7.27 (1H, t, JAB = 7.2, JBA = 7.4 Hz), 7.21 (2H, t, JAB = 7.4, JBA = 7.8 Hz), 7.14 (1H, d, J = 7.5 Hz), 3.52 (2H, s, CH2). The crystal structure of 1 was determined by X-ray diffraction (Table 1); for details, see the Supporting Information. CCDC 2055525.
Table 1. Crystal Data and Structure Refinement Details for 1 and 2
 12
formulaC9H6Ag2O4C6H5AgO3
fw393.88232.97
crystal form, colorblock, colorlessneedle, colorless
crystal size (mm)0.3 × 0.04 × 0.020.2 × 0.06 × 0.04
crystal systemorthorhombicmonoclinic
space groupPbcaC2/c
a, Å6.2548(2)27.973(3)
b, Å10.4480(3)3.8045(5)
c, Å28.3300(8)13.0369(16)
α, deg9090
β, deg90107.283(4)
γ, deg9090
Z88
V, Å31851.37(10)1324.8(3)
T, K293293
Dc, g cm–32.8262.336
μ(Mo Kα), mm–14.2162.977
θ range (deg)3.261–32.5743.051–26.352
refl. collected26,14815,269
independent refl.33401352
Rint0.03420.0275
R1a, wR2b [I ≥ 2σ(I)]0.0387, 0.07240.0211, 0.0605
GOF on F21.1841.095
a

R1 = Σ||Fo| – |Fc||/Σ|Fo|.

b

wR2 = [Σ[w(Fo2 – Fc2)2]/Σ[w(Fo2)2]]1/2.

[Ag2(μ4-nda)(H2O)2]n (2)

Compound 2 was synthesized by a method similar to 1 but utilizing 2,6-naphthalenedicarboxylic acid (H2nda, 0.216 g, 1 mmol) in place of H2hfa. Pale yellow microcrystals (including suitable for X-ray diffraction) appeared in 1–2 weeks, which were separated and air-dried to afford bioCP 2 in 47% yield relatively to silver(I) oxide. BioCP 1 is barely soluble in water (0.089 mg·mL–1). Analysis calculated (%) for 2, C12H6O4Ag2(H2O)2 + CH3CN (2 + CH3CN): C, 33.17; H, 2.58; N, 2.76. Found: C, 33.44; H, 1.95; N, 2.86. FTIR-ATR (cm–1): 3322 m ν(H2O), 3209 m ν(H2O), 1602 w, 1539 s νas(COO), 1490 m, 1383 s, 1348 s νs(COO), 1199 m, 1138 w, 1098 w, 910 w, 831 w, 777 s cm–1. 1H NMR (400 MHz, DMSO-d6): δ ppm 8.45 (2H, s), 8.00 (2H, d, J = 8.3 Hz), 7.93 (2H, d, J = 7.4 Hz). The crystal structure of 2 was determined by X-ray diffraction (Table 1); for details, see the Supporting Information. CCDC 2055526.

Synthesis of bioCP-Doped [SBO]n Films

Prior to incorporation into the [SBO]n, coordination polymers 1 or 2 were ground into fine-powder solids. Then, bioCPs were introduced in different quantities to SBO (6.5 g) at loadings of 0.05–0.5 wt %, namely, SBO/bioCP 1000:0.5, 1000:1, 1000:5, and 1000:0 (control SBO sample). The mixtures obtained were stirred for 5 min at 40 °C for uniform dispersion of bioCPs in SBO; then, tert-butyl peroxybenzoate (TBPB, 2 wt % relatively to SBO) was added. After additional homogenization during 2 min, the mixtures were placed to 9 cm Petri dishes for the preparation of thin films of biopolymers. Polymerization of SBO was carried out by heating Petri dish samples in an oven for 2 h at 120 °C, in addition to subsequent treatment at 160 °C for 4 h. After cooling, the biopolymers were detached from Petri dishes to produce thin bioCP-doped biopolymer films that were abbreviated as follows: 1-0.5%@[SBO]n, 1-0.1%@[SBO]n, and 1-0.05%@[SBO]n and 2-0.5%@[SBO]n, 2-0.1%@[SBO]n, 2-0.05%@[SBO]n, and [SBO]n (control sample). For comparative purposes, the related types of the Ag2O-doped (i.e., Ag2O-0.05%@[SBO]n, Ag2O-0.1%@[SBO]n, and Ag2O-0.5%@[SBO]n) and AgNO3-doped biopolymer films were also prepared following the above-described procedure. FTIR-ATR (cm–1): 2019 vs, 2850 s, 1730 vs, 1175 vs, 1097 s, 1051 s, 809 w, 722 m cm–1.

Preparation of bioCP-Doped [PS]n Films

Prior to incorporation into the [PS]n-based biopolymers, bioCPs 1 and 2 were ground into fine-powder solids. A mixture of PS (1 g), distilled water (10 mL), and glycerol (0.8 mL) (1:10:0.8 mass ratio) was prepared by mixing PS with water for 3 min at 80 °C, followed by adding glycerol. Then, compounds 1 or 2 were added, and the mixtures obtained were stirred for 15 min at 70 °C until reaching a complete homogenization. Then, the mixtures were poured into Petri dishes (0.09 m of diameter) and kept at 50 °C in an oven for polymerization for 24 h. The malleable biopolymer films were detached from Petri dishes to furnish the bioCP-doped [PS]n biopolymer films 1-0.5%@[PS]n and 2-0.5%@[PS]n. In parallel experiments, the control [PS]n and Ag2O-0.5%@[PS]n films were prepared for comparative purposes. FTIR-ATR (cm–1): 3300 br, 2936 m, 2886 m, 1645 w, 1456 w, 1417 w, 1335 w, 1151 m, 1105, m, 1078 m, 1020 vs, 999 vs, 923 m, 852 m cm–1.

Conclusions

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Two new silver(I) bioCPs, [Ag2(μ6-hfa)]n (1) and [Ag2(μ4-nda)(H2O)2]n (2), were easily self-assembled and fully characterized. Both compounds represent the unique examples of silver(I) bioCPs driven by homophthalate2– or 2,6-naphthalenedicarboxylate2– linkers, thus widening a limited application of these dicarboxylate ligands for designing new metal–organic architectures.
The products 1 and 2 were applied as potent antimicrobial agents for the production of a new series of hybrid bioCP-loaded biopolymer films. Two types of biopolymer films, based on the epoxidized SBO or PS, were fabricated, and their antibacterial and biofilm inhibition properties were investigated in detail against four typical types of bacteria. In fact, the Ag-doped biopolymer films were able to prevent biofilm growth, especially those composed by [PS]n for which a total biofilm inhibition was achieved in several cases. Interestingly, the efficacy of bioCPs was dependent on the biopolymer matrix, with 1 being more effective in [PS]n, while for 2, this trend was less evident, exhibiting inhibition responses of the same magnitude. However, 2@[PS]n exhibited slightly better results against P. aeruginosa and E. coli, while 2@[SBO]n was more successful against S. aureus and S. epidermidis. The usage of two model biopolymers with different permeabilities and stabilities was one of the ideas explored in the present study to obtain materials with higher or lower Ag+ release, while applying the same type of dopant.
In summary, this work contributes to an underexplored biofilm inhibition application of bioCPs and derived functional materials, also showing that highly efficient antimicrobial biopolymer films can be easily fabricated from inexpensive biobased raw materials such as soybean oil, PS, and glycerol. We believe that this study can open up new perspectives for the design and application of biopolymer materials with antimicrobial activity.

Supporting Information

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The Supporting Information is available free of charge at https://pubs.acs.org/doi/10.1021/acsami.2c03010.

  • Description of methods and experimental procedures and synthesis of bioCPs 1 and 2, detailed photographs of powders and crystals of 1 and 2, topological representations, photographs of [SBO]n and [PS]n biopolymer films, photographs of doped biopolymer films, particle size distribution analysis, ATR-FT-IR spectra, SEM-EDS data, images of biopolymer coupons in PBS solution, ICP-OES data, water absorption data, antibacterial properties of relevant Ag-based coordination polymers/MOFs, nonnormalized minimum inhibitory radius for different Ag-doped biopolymer films, TGA curves, PXRD patterns, additional antimicrobial data, and crystallographic data in CIF format (CCDC 2055525 and 2055526) (PDF)

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Author Information

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  • Corresponding Authors
    • Nuno Cerca - Centre of Biological Engineering, University of Minho, Campus de Gualtar, 4710-057 Braga, Portugal;  Present Address: LABBELS–Associate Laboratory, Braga/Guimarães, Portugal;  Email: [email protected]
    • Alexander M. Kirillov - Centro de Química Estrutural, Institute of Molecular Sciences, Departamento de Engenharia Química, Instituto Superior Técnico, Universidade de Lisboa, Av. Rovisco Pais, 1049-001 Lisbon, Portugal;  Orcidhttps://orcid.org/0000-0002-2052-5280;  Email: [email protected]
  • Authors
    • Tiago A. Fernandes - Centro de Química Estrutural, Institute of Molecular Sciences, Departamento de Engenharia Química, Instituto Superior Técnico, Universidade de Lisboa, Av. Rovisco Pais, 1049-001 Lisbon, Portugal
    • Inês F.M. Costa - Centro de Química Estrutural, Institute of Molecular Sciences, Departamento de Engenharia Química, Instituto Superior Técnico, Universidade de Lisboa, Av. Rovisco Pais, 1049-001 Lisbon, Portugal
    • Paula Jorge - Centre of Biological Engineering, University of Minho, Campus de Gualtar, 4710-057 Braga, Portugal;  Present Address: LABBELS–Associate Laboratory, Braga/Guimarães, Portugal
    • Ana Catarina Sousa - Centro de Química Estrutural, Institute of Molecular Sciences, Departamento de Engenharia Química, Instituto Superior Técnico, Universidade de Lisboa, Av. Rovisco Pais, 1049-001 Lisbon, Portugal;  Área Departamental de Engenharia Química, ISEL─Instituto Superior de Engenharia de Lisboa, Instituto Politécnico de Lisboa, R. Conselheiro Emídio Navarro, 1, 1959-007 Lisbon, Portugal
    • Vânia André - Centro de Química Estrutural, Institute of Molecular Sciences, Departamento de Engenharia Química, Instituto Superior Técnico, Universidade de Lisboa, Av. Rovisco Pais, 1049-001 Lisbon, Portugal;  Orcidhttps://orcid.org/0000-0001-5599-8355
    • Rafaela G. Cabral - Centro de Química Estrutural, Institute of Molecular Sciences, Departamento de Engenharia Química, Instituto Superior Técnico, Universidade de Lisboa, Av. Rovisco Pais, 1049-001 Lisbon, Portugal;  Área Departamental de Engenharia Química, ISEL─Instituto Superior de Engenharia de Lisboa, Instituto Politécnico de Lisboa, R. Conselheiro Emídio Navarro, 1, 1959-007 Lisbon, Portugal
  • Notes
    The authors declare no competing financial interest.

Acknowledgments

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This study was supported by the Foundation for Science and Technology (FCT) (projects LISBOA-01-0145-FEDER-029697, PTDC/QUI-QIN/29697/2017, UIDP/00100/2020, UIDB/00100/2020, LA/P/0056/2020, and REM2013; contracts under DL no. 57/2016, CEECIND/02725/2018, and CEECIND/00194/2020) as well as ISEL (IPL/2021/Naf4Med3D_ISEL).

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    A novel Co based metal-org. framework (MOF) was tested as an antibacterial agent and is highly effective at inactivating model microorganisms such as Gram-neg. bacteria, Escherichia coli (strains DH5alpha and XL1-Blue). In Co4, the Co serves as a central element and an octa-topic carboxylate ligand, tetrakis[(3,5-dicarboxyphenyl)oxamethyl]methane (TDM8-) serves as a bridging linker. X-ray crystallog. studies indicate that Co-TDM crystallizes in tetragonal space group P‾421m with a porous 3-dimensional framework. The potency of the Co-TDM disinfectant was evaluated using a minimal bactericidal concn. (MBC) benchmark and is 10-15 ppm within a short incubation time period (<60 min). Compared with previous work using Ag nanoparticles and Ag-modified TiO2 nanocomposites over the same time period, the MBC and effectiveness of Co-TDM are superior. Electron microscopy images indicate that the Co-TDM displayed distinctive grain boundaries and well-developed reticulates. The Co active sites rapidly catalyzed the lipid peroxidn., causing rupture of the bacterial membrane followed by inactivation, with 100% recycling and high persistence (>4 wk). This MOF-based approach may lead to a new paradigm for MOF applications in diverse biol. fields due to their inherent porous structure, tunable surface functional groups, and adjustable metal coordination environments.
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    Wang, P.-L.; Xie, L.-H.; Joseph, E. A.; Li, J.-R.; Su, X.-O.; Zhou, H.-C. Metal-Organic Frameworks for Food Safety. Chem. Rev. 2019, 119, 10638– 10690,  DOI: 10.1021/acs.chemrev.9b00257
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    Metal-Organic Frameworks for Food Safety
    Wang, Pei-Long; Xie, Lin-Hua; Joseph, Elizabeth A.; Li, Jian-Rong; Su, Xiao-Ou; Zhou, Hong-Cai
    Chemical Reviews (Washington, DC, United States) (2019), 119 (18), 10638-10690CODEN: CHREAY; ISSN:0009-2665. (American Chemical Society)
    A review. Food safety is a prevalent concern around the world. As such, detection, removal, and control of risks and hazardous substances present from harvest to consumption will always be necessary. Metal-org. frameworks (MOFs), a class of functional materials, possess unique phys. and chem. properties, demonstrating promise in food safety applications. In this review, the synthesis and porosity of MOFs are first introduced by some representative examples that pertain to the field of food safety. Following that, the application of MOFs and MOF-based materials in food safety monitoring, food processing, covering preservation, sanitation, and packaging is overviewed. Future perspectives, as well as potential opportunities and challenges faced by MOFs in this field will also be discussed. This review aims to promote the development and progress of MOF chem. and application research in the field of food safety, potentially leading to novel solns.
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    Wyszogrodzka, G.; Marszałek, B.; Gil, B.; Dorożyński, P. Metal-Organic Frameworks: Mechanisms of Antibacterial Action and Potential Applications. Drug Discovery Today 2016, 21, 1009– 1018,  DOI: 10.1016/j.drudis.2016.04.009
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    Metal-organic frameworks: mechanisms of antibacterial action and potential applications
    Wyszogrodzka, Gabriela; Marszalek, Bartosz; Gil, Barbara; Dorozynski, Przemyslaw
    Drug Discovery Today (2016), 21 (6), 1009-1018CODEN: DDTOFS; ISSN:1359-6446. (Elsevier Ltd.)
    The growing resistance of pathogens to conventional antibiotics has become a public health problem and raises the need to seek new effective solns. Metal-org. frameworks (MOFs) are porous, hybrid materials comprising metal ions linked by org. binding ligands. The possibility of using a variety of chem. building components in MOFs enables the formation of structures with desired properties. They can act as a reservoir of metal ions, providing their gradual release and resulting in a sustained antibacterial action analogous to that proposed for metal/metal oxide nanoparticles (NPs) but different to that of antibiotics. These features make MOFs promising candidates for pharmaceutical and biomedical applications, as illustrated by examples discussed in this review.
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    Cheung, Y. H.; Ma, K.; van Leeuwen, H. C.; Wasson, M. C.; Wang, X.; Idrees, K. B.; Gong, W.; Cao, R.; Mahle, J. J.; Islamoglu, T.; Peterson, G. W.; de Koning, M. C.; Farha, O. K.; Farha, O. K. Immobilized Regenerable Active Chlorine within a Zirconium-Based MOF Textile Composite to Eliminate Biological and Chemical Threats. J. Am. Chem. Soc. 2021, 143, 16777– 16785,  DOI: 10.1021/jacs.1c08576
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    Immobilized Regenerable Active Chlorine within a Zirconium-Based MOF Textile Composite to Eliminate Biological and Chemical Threats
    Cheung, Yuk Ha; Ma, Kaikai; van Leeuwen, Hans C.; Wasson, Megan C.; Wang, Xingjie; Idrees, Karam B.; Gong, Wei; Cao, Ran; Mahle, John J.; Islamoglu, Timur; Peterson, Gregory W.; de Koning, Martijn C.; Xin, John H.; Farha, Omar K.
    Journal of the American Chemical Society (2021), 143 (40), 16777-16785CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)
    The most recent global health crisis caused by the SARS-CoV-2 outbreak and the alarming use of chem. warfare agents highlight the necessity to produce efficient protective clothing and masks against biohazard and chem. threats. However, the development of a multifunctional protective textile is still behind to supply adequate protection for the public. To tackle this challenge, we designed multifunctional and regenerable N-chlorine based biocidal and detoxifying textiles using a robust zirconium metal-org. framework (MOF), UiO-66-NH2, as a chlorine carrier which can be easily coated on textile fibers. A chlorine bleaching converted the amine groups located on the MOF linker to active N-chlorine structures. The fibrous composite exhibited rapid biocidal activity against both Gram-neg. bacteria (E. coli) and Gram-pos. bacteria (S. aureus) with up to a 7 log redn. within 5 min for each strain as well as a 5 log redn. of SARS-CoV-2 within 15 min. Moreover, the active chlorine loaded MOF/fiber composite selectively and rapidly degraded sulfur mustard and its chem. simulant 2-chloroethyl Et sulfide (CEES) with half-lives less than 3 min. The versatile MOF-based fibrous composite designed here has the potential to serve as protective cloth against both biol. and chem. threats.
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    Giliopoulos, D.; Zamboulis, A.; Giannakoudakis, D.; Bikiaris, D.; Triantafyllidis, K. Polymer/Metal Organic Framework (MOF) Nanocomposites for Biomedical Applications. Molecules 2020, 25, 185,  DOI: 10.3390/molecules25010185
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    Polymer/metal organic framework (MOF) nanocomposites for biomedical applications
    Giliopoulos, Dimitrios; Zamboulis, Alexandra; Giannakoudakis, Dimitrios; Bikiaris, Dimitrios; Triantafyllidis, Konstantinos
    Molecules (2020), 25 (1), 185CODEN: MOLEFW; ISSN:1420-3049. (MDPI AG)
    A review. The utilization of polymer/metal org. framework (MOF) nanocomposites in various biomedical applications has been widely studied due to their unique properties that arise from MOFs or hybrid composite systems. This review focuses on the types of polymer/MOF nanocomposites used in drug delivery and imaging applications. Initially, a comprehensive introduction to the synthesis and structure of MOFs and bio-MOFs is presented. Subsequently, the properties and the performance of polymer/MOF nanocomposites used in these applications are examd., in relation to the approach applied for their synthesis: (i) non-covalent attachment, (ii) covalent attachment, (iii) polymer coordination to metal ions, (iv) MOF encapsulation in polymers, and (v) other strategies. A crit. comparison and discussion of the effectiveness of polymer/MOF nanocomposites regarding their synthesis methods and their structural characteristics is presented.
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    Jaros, S. W.; Guedes da Silva, M. F. C.; Florek, M.; Smoleński, P.; Pombeiro, A. J. L.; Kirillov, A. M. Silver(I) 1,3,5-Triaza-7-Phosphaadamantane Coordination Polymers Driven by Substituted Glutarate and Malonate Building Blocks: Self-Assembly Synthesis, Structural Features, and Antimicrobial Properties. Inorg. Chem. 2016, 55, 5886– 5894,  DOI: 10.1021/acs.inorgchem.6b00186
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    Silver(I) 1,3,5-Triaza-7-phosphaadamantane Coordination Polymers Driven by Substituted Glutarate and Malonate Building Blocks: Self-Assembly Synthesis, Structural Features, and Antimicrobial Properties
    Jaros, Sabina W.; Guedes da Silva, M. Fatima C.; Florek, Magdalena; Smolenski, Piotr; Pombeiro, Armando J. L.; Kirillov, Alexander M.
    Inorganic Chemistry (2016), 55 (12), 5886-5894CODEN: INOCAJ; ISSN:0020-1669. (American Chemical Society)
    Three new bioactive silver(I) coordination polymers formulated as [Ag2(μ2-PTA)(μ3-PTA)(μ2-pga)(H2O)]n·6H2O (1), [Ag2(μ2-PTA)(μ3-PTA)(Hpmal)2]n·2H2O (2), and [Ag(μ3-PTA) (Hdmga)]n (3) were self-assembled from Ag2O, 1,3,5-triaza-7-phosphaadamantane (PTA), and a substituted dicarboxylic acid (3-phenylglutaric acid (H2pga), phenylmalonic acid (H2pmal), or 3,3-dimethylglutaric acid (H2dmga)) as an ancillary ligand. Compds. 1-3 were fully characterized by IR and NMR spectroscopy, ESI-MS(±), elemental anal., and single-crystal x-ray diffraction, revealing that their architectural and topol. diversity is governed by structural modulation of a dicarboxylate building block. The structures vary from a 1D cyclic chain with the SP 1-periodic net (4,4)(0,2) topol. in 2 to distinct 2D metal-org. layers with the cem-d and hcb topologies in 1 and 3, resp. In addn., compds. 1-3 exhibit a notable antimicrobial efficiency against a panel of common Gram-neg. (E. coli and P. aeruginosa) and Gram-pos. (S. aureus) bacteria and yeast (C. albicans). The best normalized min. inhibitory concns. (normalized MIC) of 11-23 nmol mL-1 (for bacterial strains) or 68 nmol mL-1 (for a yeast strain) are shown by compd. 2, and the eventual structure-bioactivity correlations are discussed.
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    Jaros, S. W.; Guedes da Silva, M. F. C.; Król, J.; Conceição Oliveira, M.; Smoleński, P.; Pombeiro, A. J. L.; Kirillov, A. M. Bioactive Silver–Organic Networks Assembled from 1,3,5-Triaza-7-Phosphaadamantane and Flexible Cyclohexanecarboxylate Blocks. Inorg. Chem. 2016, 55, 1486– 1496,  DOI: 10.1021/acs.inorgchem.5b02235
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    Bioactive Silver-Organic Networks Assembled from 1,3,5-Triaza-7-phosphaadamantane and Flexible Cyclohexanecarboxylate Blocks
    Jaros, Sabina W.; Guedes da Silva, M. Fatima C.; Krol, Jaroslaw; Conceicao Oliveira, M.; Smolenski, Piotr; Pombeiro, Armando J. L.; Kirillov, Alexander M.
    Inorganic Chemistry (2016), 55 (4), 1486-1496CODEN: INOCAJ; ISSN:0020-1669. (American Chemical Society)
    Three novel bioactive silver-org. networks, namely, the 2D polymer [Ag(μ3-PTA)(chc)]n·n(Hchc)·2nH2O (1), the 3D bioMOF [Ag2(μ3-PTA)2(μ2-chdc)]n·5nH2O (2), and the 2D polymer [Ag2(μ2-PTA)2(μ4-H2chtc)]n·6nH2O (3), were constructed from 1,3,5-triaza-7-phosphaadamantane (PTA) and various flexible cyclohexanecarboxylic acids as building blocks {cyclohexanecarboxylic (Hchc), 1,4-cyclohexanedicarboxylic (H2chdc), and 1,2,4,5-cyclohexanetetracarboxylic (H4chtc) acid, resp.}. The obtained products 1-3 were fully characterized by IR and NMR spectroscopy, ESI-MS(±) spectrometry, elemental and thermogravimetric (TGA) analyses, and single-crystal and powder X-ray diffraction. Their structural diversity originates from distinct coordination modes of cyclohexanecarboxylate moieties as well as from the presence of unconventional N,N,P-tridentate or N,P-bidentate PTA spacers. Topol. classification of underlying metal-org. networks was performed, disclosing the hcb, 4,4L28, and a rare fsc-3,4-Pbcn-3 topol. in 1, 2, and 3, resp. Moreover, combination of aq. soly. (S25°C ≈ 4-6 mg mL-1), air stability, and appropriate coordination environments around silver centers favors a release of bioactive Ag+ ions by 1-3, which thus act as potent antibacterial and antifungal agents against Gram-pos. (S. aureus) and Gram-neg. (E. coli and P. aeruginosa) bacteria as well as a yeast (C. albicans). The best normalized min. inhibitory concns. (normalized MIC) of 10-18 (for bacterial strains) or 57 nmol mL-1 (for a yeast strain) were achieved. Detailed ESI-MS studies were performed, confirming the relative stability of 1-3 in soln. and giving addnl. insight on the self-assembly formation of polycarboxylate Ag-PTA derivs. and their crystal growth process.
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    Smoleński, P.; Jaros, S. W.; Pettinari, C.; Lupidi, G.; Quassinti, L.; Bramucci, M.; Vitali, L. A.; Petrelli, D.; Kochel, A.; Kirillov, A. M. New Water-Soluble Polypyridine Silver(I) Derivatives of 1,3,5-Triaza-7-Phosphaadamantane (PTA) with Significant Antimicrobial and Antiproliferative Activities. Dalton Trans. 2013, 42, 6572– 6581,  DOI: 10.1039/c3dt33026e
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    New water-soluble polypyridine silver(I) derivatives of 1,3,5-triaza-7-phosphaadamantane (PTA) with significant antimicrobial and antiproliferative activities
    Smolenski, Piotr; Jaros, Sabina W.; Pettinari, Claudio; Lupidi, Giulio; Quassinti, Luana; Bramucci, Massimo; Vitali, Luca A.; Petrelli, Dezemona; Kochel, Andrzej; Kirillov, Alexander M.
    Dalton Transactions (2013), 42 (18), 6572-6581CODEN: DTARAF; ISSN:1477-9226. (Royal Society of Chemistry)
    Silver(I) coordination polymers [Ag(N-N)(μ-PTA)]n(X)n (1, 2, 4-8, 10, 11) and discrete monomers [Ag(N-N)(PTA)2](X) (3, 9) {N-N = bpy (1-3), dtbpy (4), neocup (5, 6), phen (7-9), dione (10, 11); X = NO3 (1, 3, 5, 7, 9, 10), PF6 (2, 4, 6, 8, 11)} were generated by self-assembly reactions, in MeOH at ∼25°, of AgNO3 or AgPF6 with 1,3,5-triaza-7-phosphaadamantane (PTA) and the corresponding polypyridines, 2,2'-bipyridine (bpy), 4,4'-di-tert-butyl-2,2'-bipyridine (dtbpy), 1,10-phenanthroline (phen), 2,9-dimethyl-1,10-phenanthroline (neocup) and 1,10-phenanthroline-5,6-dione. The compds. were obtained as air and light stable solids and characterized by IR, 1H and 31P{1H} NMR spectroscopy, ESI+-MS and elemental analyses. The crystal structure of 1 was detd. by single crystal x-ray diffraction anal., revealing infinite 1-dimensional (1D) linear chains driven by μ-PTA N,P-linkers. Apart from representing the first examples of the metal-PTA derivs. bearing polypyridine ligands, 1-11 also feature soly. in water (S25°C ≈ 4-18 mg mL-1). Selected compds. (1, 3, 5, 7, 9 and 10) were thus tested for their biol. properties and found to exhibit significant antibacterial and antifungal activities, screened in vitro against the std. strains of Staphylococcus aureus, Staphylococcus pyogenes, Staphylococcus pneumoniae, Staphylococcus sanguinis, Staphylococcus mutans, Enterococcus faecalis, Pseudomonas aeruginosa, Escherichia coli and Candida albicans. Also, the compds. 5, 7, 9 and 10 show a pronounced antiproliferative activity against human malignant melanoma (A375), and the effects on the inhibition of tumor cells in vitro are in agreement with the DNA-binding studies.
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    Fernandes, T. A.; Costa, I. F. M.; Jorge, P.; Sousa, A. C.; André, V.; Cerca, N.; Kirillov, A. M. Silver(I) Coordination Polymers Immobilized into Biopolymer Films for Antimicrobial Applications. ACS Appl. Mater. Interfaces 2021, 13, 12836– 12844,  DOI: 10.1021/acsami.0c19446
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    Silver(I) Coordination Polymers Immobilized into Biopolymer Films for Antimicrobial Applications
    Fernandes, Tiago A.; Costa, Ines F. M.; Jorge, Paula; Sousa, Ana Catarina; Andre, Vania; Cerca, Nuno; Kirillov, Alexander M.
    ACS Applied Materials & Interfaces (2021), 13 (11), 12836-12844CODEN: AAMICK; ISSN:1944-8244. (American Chemical Society)
    This study describes a template-mediated self-assembly synthesis, full characterization, and structural features of two new silver-based bioactive coordination polymers (CPs) and their immobilization into acrylated epoxidized soybean oil (ESOA) biopolymer films for antimicrobial applications. The 3D silver(I) CPs [Ag4(μ8-H2pma)2]n·4nH2O (1) and [Ag5(μ6-H0.5tma)2(H2O)4]n·2nH2O (2) were generated from AgNO3 and pyromellitic (H4pma) or trimesic (H3tma) acid, also using N,N'-dimethylethanolamine (Hdmea) as a template. Both 1 and 2 feature the intricate 3D layer-pillared structures driven by distinct polycarboxylate blocks. Topol. anal. revealed binodal nets with the flu and tcj/hc topol. in 1 and 2, resp. These CPs were used for fabricating new hybrid materials, namely, by doping the [ESOA]n biopolymer films with very low amts. of 1 and 2 (0.05, 0.1, and 0.5%). Their antimicrobial activity and ability to impair bacterial biofilm formation were investigated in detail against both Gram-pos. (Staphylococcus epidermidis and Staphylococcus aureus) and Gram-neg. (Pseudomonas aeruginosa and Escherichia coli) bacteria. Both silver(I) CPs and derived biopolymer films showed activity against all the tested bacteria in a concn.-dependent manner. Compd. 1 exhibited a more pronounced activity, esp. in preventing biofilm growth, with mean bacterial load redns. ranging from 3.7 to 4.3 log against the four bacteria (99.99% bacterial eradication). The present work thus opens up antibiofilm applications of CP-doped biopolymers, providing new perspectives and very promising results for the design of functional biomaterials.
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    Abram, S. L.; Fromm, K. M. Handling (Nano)Silver as Antimicrobial Agent: Therapeutic Window, Dissolution Dynamics, Detection Methods and Molecular Interactions. Chem.─Eur. J. 2020, 26, 10948– 10971,  DOI: 10.1002/chem.202002143
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    Handling (Nano)Silver as Antimicrobial Agent: Therapeutic Window, Dissolution Dynamics, Detection Methods and Molecular Interactions
    Abram, Sarah-Luise; Fromm, Katharina M.
    Chemistry - A European Journal (2020), 26 (48), 10948-10971CODEN: CEUJED; ISSN:0947-6539. (Wiley-VCH Verlag GmbH & Co. KGaA)
    A review. Silver is an antimicrobial agent well known since antiquity. With the emergence of multiresistant bacteria, it has come back into the focus of research, and ionic as well as nano-sized silver have been studied in vitro and in vivo. The results are controversial, silver being discussed as the "silver bullet" or a "wolf in sheep's clothing". A thorough search of literature from chem., materials and environmental science, biol. and medicine led to this Review which summarizes the potential use of silver and its compds. in medicine, ongoing processes of dissoln. and the different methods by which this usefulness can be evaluated. It also highlights the therapeutic window of silver, mechanistic interactions of silver and biol. media as well as best practices for handling silver in a biomedical environment. This Review reflects the current knowhow and observations, and may thus give hints and guidelines to understand and interpret the obsd. effects.
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    Eckhardt, S.; Brunetto, P. S.; Gagnon, J.; Priebe, M.; Giese, B.; Fromm, K. M. Nanobio Silver: Its Interactions with Peptides and Bacteria, and Its Uses in Medicine. Chem. Rev. 2013, 113, 4708– 4754,  DOI: 10.1021/cr300288v
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    Nanobio Silver: Its Interactions with Peptides and Bacteria, and Its Uses in Medicine
    Eckhardt, Sonja; Brunetto, Priscilla S.; Gagnon, Jacinthe; Priebe, Magdalena; Giese, Bernd; Fromm, Katharina M.
    Chemical Reviews (Washington, DC, United States) (2013), 113 (7), 4708-4754CODEN: CHREAY; ISSN:0009-2665. (American Chemical Society)
    A review of the interactions of silver with amino acids, peptides and bacteria and the various types of silver-contg. compds and nanomaterials and their biocompatibilities.
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    Horcajada, P.; Gref, R.; Baati, T.; Allan, P. K.; Maurin, G.; Couvreur, P.; Férey, G.; Morris, R. E.; Serre, C. Metal-Organic Frameworks in Biomedicine. Chem. Rev. 2012, 112, 1232– 1268,  DOI: 10.1021/cr200256v
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    Metal-Organic Frameworks in Biomedicine
    Horcajada, Patricia; Gref, Ruxandra; Baati, Tarek; Allan, Phoebe K.; Maurin, Guillaume; Couvreur, Patrick; Ferey, Gerard; Morris, Russell E.; Serre, Christian
    Chemical Reviews (Washington, DC, United States) (2012), 112 (2), 1232-1268CODEN: CHREAY; ISSN:0009-2665. (American Chemical Society)
    A review. Coordination polymers or MOFs (metal-org. frameworks) as porous solids for biomedical are reviewed.
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    Zheng, K.; Setyawati, M. I.; Leong, D. T.; Xie, J. Embedding Ultrasmall Ag Nanoclusters in Luria-Bertani Extract via Light Irradiation for Enhanced Antibacterial Activity. Coord. Chem. Rev. 2018, 357, 1– 17,  DOI: 10.1016/j.ccr.2017.11.019
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    Antimicrobial silver nanomaterials
    Zheng, Kaiyuan; Setyawati, Magdiel Inggrid; Leong, David Tai; Xie, Jianping
    Coordination Chemistry Reviews (2018), 357 (), 1-17CODEN: CCHRAM; ISSN:0010-8545. (Elsevier B.V.)
    Antibiotic resistance is considered as one of the greatest health threats worldwide, and we are in a staring competition with microbes as antibiotic resistance mounts faster than our current rate of developing new and effective antibiotics. Therefore, newer metal-based antimicrobial agents with easily tuned physicochem. properties have been developed to fight against these antibiotic resistant bacteria. In this review, we begin with describing the mode of action of silver nanoparticles (Ag NPs) in damaging the bacterial extracellular membrane and their intracellular components that allows them to exhibit wide spectrum antimicrobial effect. The review also contains our insights on understanding not only the correlation between the NPs' physicochem. properties and their bactericidal mode of action but also the possible strategies to tune these physicochem. properties to optimize their bactericidal properties. The second focus of this review is on the emerging and highly efficient antimicrobial agents, ultrasmall Ag nanoclusters (Ag NCs). Ag NCs are ultrasmall NPs with core sizes less than 2 nm, and they contain "countable" Ag atoms as the core, which is protected by a certain no. of org. ligands. The atomically precise property of Ag NCs provides a good platform to design and manipulate Ag NCs at at. level to achieve optimized antimicrobial efficacy, which also favor the antimicrobial mechanism study.
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    Davoudi, Z. M.; Kandjani, A. E.; Bhatt, A. I.; Kyratzis, I. L.; O’Mullane, A. P.; Bansal, V. Hybrid Antibacterial Fabrics with Extremely High Aspect Ratio Ag/AgTCNQ Nanowires. Adv. Funct. Mater. 2014, 24, 1047– 1053,  DOI: 10.1002/adfm.201302368
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    Hybrid Antibacterial Fabrics with Extremely High Aspect Ratio Ag/AgTCNQ Nanowires
    Davoudi, Zahra Mohammad; Kandjani, Ahmad Esmaielzadeh; Bhatt, Anand I.; Kyratzis, Ilias L.; O'Mullane, Anthony P.; Bansal, Vipul
    Advanced Functional Materials (2014), 24 (8), 1047-1053CODEN: AFMDC6; ISSN:1616-301X. (Wiley-VCH Verlag GmbH & Co. KGaA)
    This study reports the synthesis of extremely high aspect ratios (>3000) org. semiconductor nanowires of Ag-tetracyanoquinodimethane (AgTCNQ) on the surface of a flexible Ag fabric for the first time. These one-dimensional (1D) hybrid Ag/AgTCNQ nanostructures are attained by a facile, soln.-based spontaneous reaction involving immersion of Ag fabrics in an acetonitrile soln. of TCNQ. Further, it is discovered that these AgTCNQ nanowires show outstanding antibacterial performance against both Gram neg. and Gram pos. bacteria, which outperforms that of pristine Ag. The outcomes of this study also reflect upon a fundamentally important aspect that the antimicrobial performance of Ag-based nanomaterials may not necessarily be solely due to the amt. of Ag+ ions leached from these nanomaterials, but that the nanomaterial itself may also play a direct role in the antimicrobial action. Notably, the applications of metal-org. semiconducting charge transfer complexes of metal-7,7,8,8-tetracyanoquinodimethane (TCNQ) have been predominantly restricted to electronic applications, except from our recent reports on their (photo)catalytic potential and the current case on antimicrobial prospects. This report on growth of these metal-TCNQ complexes on a fabric not only widens the window of these interesting materials for new biol. applications, it also opens the possibilities for developing large-area flexible electronic devices by growing a range of metal-org. semiconducting materials directly on a fabric surface.
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    Chen, J.; Wang, F.; Liu, Q.; Du, J. Antibacterial Polymeric Nanostructures for Biomedical Applications. Chem. Commun. 2014, 50, 14482– 14493,  DOI: 10.1039/c4cc03001j
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    Antibacterial polymeric nanostructures for biomedical applications
    Chen, Jing; Wang, Fangyingkai; Liu, Qiuming; Du, Jianzhong
    Chemical Communications (Cambridge, United Kingdom) (2014), 50 (93), 14482-14493CODEN: CHCOFS; ISSN:1359-7345. (Royal Society of Chemistry)
    A review. The high incidence of bacterial infection and the growing resistance of bacteria to conventional antibiotics have resulted in the strong need for the development of new generation of antibiotics. Nano-sized particles have been considered as novel antibacterial agents with high surface area and high reactivity. The overall antibacterial properties of antimicrobial nanostructures can be significantly enhanced compared with conventional antibacterial agents not in a regular nanostructure, showing a better effect in inhibiting the growth and reprodn. of microbials such as bacteria and fungi, etc. In this review, recent advances in the research and applications of antimicrobial polymeric nanostructures have been highlighted, including silver-decorated polymer micelles and vesicles, antimicrobial polymer micelles and vesicles, and antimicrobial peptide-based vesicles, etc. Furthermore, we proposed the current challenges and future research directions in the field of antibacterial polymeric nanostructures for the real-world biomedical applications.
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    Arenas-Vivo, A.; Amariei, G.; Aguado, S.; Rosal, R.; Horcajada, P. An Ag-loaded Photoactive Nano-metal Organic Framework as a Promising Biofilm Treatment. Acta Biomater. 2019, 97, 490– 500,  DOI: 10.1016/j.actbio.2019.08.011
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    An Ag-loaded photoactive nano-metal organic framework as a promising biofilm treatment
    Arenas-Vivo, Ana; Amariei, Georgiana; Aguado, Sonia; Rosal, Roberto; Horcajada, Patricia
    Acta Biomaterialia (2019), 97 (), 490-500CODEN: ABCICB; ISSN:1742-7061. (Elsevier Ltd.)
    Surface biofilm inhibition is still currently a considerable challenge. Among other organisms, Staphylococcus aureus is notable for its ability to form a strong biofilm with proved resistance to chemotherapy. Contamination of high-touch surfaces with S. aureus biofilm not only promotes disease spread but also generates tremendous health-assocd. costs. Therefore, development of new bactericidal and antiadhesive surface coatings is a priority. Considering that metal-org. frameworks (MOFs) have recently emerged as promising antibacterial agents, we originally report here the synthesis of a multi-active silver-contg. nanoscaled MOF composite as a potential surface coating against S. aureus biofilm owing to a triple effect: intrinsic bactericide activity of the MOF, biocidal character of silver nanoparticles (AgNPs), and photoactivity after UVA irradn. AgNPs were successfully entrapped within the benchmarked nanoscaled porous photoactive titanium(IV) aminoterephthalate MIL-125(Ti)NH2 using a simple and efficient impregnation-redn. method. After complete characterization of the composite thin film, its antibacterial and anti-adherent properties were fully evaluated. After UVA irradn., the composite coating exhibited relevant bacterial inhibition and detachment, improved ligand-to-cluster charge transfer, and steady controlled delivery of Ag+. These promising results establish the potential of this composite as an active coating for biofilm treatment on high-touch surfaces (e.g., surgical devices, door knobs, and rail bars). Surface contamination due to bacterial biofilm formation is still a demanding issue, as it causes severe disease spread. One possible soln. is the development of antifouling and antibacterial surface coatings. In this work, we originally propose the use of photoactive metal-org. frameworks (MOFs) for biofilm treatment. The novelty of this work relies on the following: i. the treatment of strongly contaminated surfaces, as previous studies with MOFs have exclusively addressed biofilm prevention; ii. this pioneering work reports both antiadherent effect, which removes the biofilm, and bacterial inhibition; iii. our original successful strategy has never been proposed thus far, involving the multi-active combination of 1. intrinsic antibacterial effect of a photoactive titanium-based nanoMOF, 2. immobilization of biocide silver nanoparticles, and 3. improved anti-bioadherent effect upon irradn. of the composite coating.
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    Nishanthi, S. T.; Yadav, K. K.; Baruah, A.; Vaghasiya, K.; Verma, R. K.; Ganguli, A. K.; Jha, M. Nanostructured Silver Decorated Hollow Silica and their Application in the Treatment of Microbial Contaminated Water at Room Temperature. New J. Chem. 2019, 43, 8993– 9001,  DOI: 10.1039/c9nj01049a
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    Nanostructured silver decorated hollow silica and their application in the treatment of microbial contaminated water at room temperature
    Nishanthi, S. T.; Yadav, Krishna Kumar; Baruah, Arabinda; Vaghasiya, Kalpesh; Verma, Rahul Kumar; Ganguli, Ashok K.; Jha, Menaka
    New Journal of Chemistry (2019), 43 (23), 8993-9001CODEN: NJCHE5; ISSN:1144-0546. (Royal Society of Chemistry)
    The present study describes the synthesis of mesoporous silicon dioxide (silica) spheres decorated with silver nanoparticles and the investigation of their antimicrobial properties. The sol-gel method was used for the synthesis of mesoporous hollow silica spheres using tetra-Et orthosilicate (TEOS) as the silica source. Uniform hollow spheres (∼300 nm) with a thin shell of silica (∼40 nm) and a high surface area (516 m2 g-1) were obtained after calcination at 550 °C. Furthermore, silver nanoparticles were decorated on the surface of the hollow structure of silica by the adsorption of silver ions at various concns. followed by redn. using sodium borohydride. Microscopic studies showed that metallic silver was uniformly distributed over the surface of the hollow silica. The as-obtained silver decorated hollow silica exhibited an excellent antibacterial activity against Escherichia coli (E. coli) compared to that of bare hollow silica, which makes them suitable candidates for the economical treatment of bacteria-contaminated water.
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    Zhang, Y.; Sun, P.; Zhang, L.; Wang, Z.; Wang, F.; Dong, K.; Liu, Z.; Ren, J.; Qu, X. Silver-Infused Porphyrinic Metal–Organic Framework: Surface-Adaptive, On-Demand Nanoplatform for Synergistic Bacteria Killing and Wound Disinfection. Adv. Funct. Mater. 2019, 29, 1808594,  DOI: 10.1002/adfm.201808594
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    Marchetti, F.; Palmucci, J.; Pettinari, C.; Pettinari, R.; Marangoni, M.; Ferraro, S.; Giovannetti, R.; Scuri, S.; Grappasonni, I.; Cocchioni, M.; Maldonado Hodar, F. J.; Gunnella, R. Preparation of Polyethylene Composites Containing Silver(I) Acylpyrazolonato Additives and SAR Investigation of Their Antibacterial Activity. ACS Appl. Mater. Interfaces 2016, 8, 29676– 29687,  DOI: 10.1021/acsami.6b09742
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    Preparation of Polyethylene Composites Containing Silver(I) Acylpyrazolonato Additives and SAR Investigation of their Antibacterial Activity
    Marchetti, Fabio; Palmucci, Jessica; Pettinari, Claudio; Pettinari, Riccardo; Marangoni, Mirko; Ferraro, Stefano; Giovannetti, Rita; Scuri, Stefania; Grappasonni, Iolanda; Cocchioni, Mario; Maldonado Hodar, Francisco Jose; Gunnella, Roberto
    ACS Applied Materials & Interfaces (2016), 8 (43), 29676-29687CODEN: AAMICK; ISSN:1944-8244. (American Chemical Society)
    Novel composite materials PEn (n = 1-9) have been prepd. by an easily up-scalable embedding procedure of three different families of Ag(I) acylpyrazolonato complexes in polyethylene (PE) matrix. In details, PE1-PE3 composites contain polynuclear [Ag(QR)]n complexes, PE4-PE6 contain mononuclear [Ag(QR)(L)m] complexes and PE7-PE9 are loaded with mononuclear [Ag(QR) (PPh3)2] complexes, resp. (where L = 1-methylimidazole or 2-ethylimidazole, m = 1 or 2, and HQR = 1-phenyl-3-methyl-4-RC(=O)-5-pyrazolone, where in detail HQfb, R = -CF2CF2CF3; HQcy, R = -cyclo-C6H11; HQbe, R = -C(H)=C(CH3)2). The PEn composites, prepd. by using a 1:1000 wt./wt. silver additive/polyethylene ratio, have been characterized in bulk by IR spectroscopy and TGA analyses, which confirmed that the properties of polyethylene matrix are essentially unchanged. AFM, SEM, and EDX surface techniques show that silver additives form agglomerates with dimensions 10-100 μm on the polyethylene surface, with a slight increment of surface roughness of pristine plastic within 50 nm. However, the elastic properties of the composites are essentially the same of PE. The antibacterial activity of all composites has been tested against three bacterial strains (E. coli, P. aeruginosa and S. aureus) and results show that two classes of composites, PE1-PE3 and PE4-PE6, display high and persistent bactericidal and bacteriostatic activity, comparable to PE embedded with AgNO3. By contrast, composites PE7-PE9 exhibit a reduced antibacterial action. Contact and release tests in several conditions for specific migration of Ag+ from plastics, indicate a very limited but time persistent release of silver ions from PE1-PE6 composites, thus suggesting that they are potential antibacterial materials for future applications. Instead, PE7-PE9 almost do not release silver, only trace levels of silver ions being detected, in accordance with their reduced antibacterial action. None of the composites is toxic against higher organisms, as confirmed by D. magna test of ecotoxicity.
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    Bhargava, A.; Pareek, V.; Roy Choudhury, S.; Panwar, J.; Karmakar, S. Superior Bactericidal Efficacy of Fucose-Functionalized Silver Nanoparticles against Pseudomonas aeruginosa PAO1 and Prevention of Its Colonization on Urinary Catheters. ACS Appl. Mater. Interfaces 2018, 10, 29325– 29337,  DOI: 10.1021/acsami.8b09475
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    Superior Bactericidal Efficacy of Fucose-Functionalized Silver Nanoparticles against Pseudomonas aeruginosa PAO1 and Prevention of Its Colonization on Urinary Catheters
    Bhargava, Arpit; Pareek, Vikram; Roy Choudhury, Subhasree; Panwar, Jitendra; Karmakar, Surajit
    ACS Applied Materials & Interfaces (2018), 10 (35), 29325-29337CODEN: AAMICK; ISSN:1944-8244. (American Chemical Society)
    Pseudomonas aeruginosa, a Gram-neg. rod-shaped bacterium is a notorious pathogen causing chronic infections. Its ability to form antibiotic-resistant biofilm has raised the need for the development of alternative treatment approaches. An ideal alternate can be silver nanoparticles known for their strong yet tunable bactericidal activity. However, their use in com. in vivo medicine could not see the light of the day because of the unwanted toxicity of silver in the host cells at higher concns. Thus, strategies which can modulate the bacterial cell-silver nanoparticle interactions thereby reducing the amt. of nanoparticles required to kill a typical no. of bacterial cells are utmost welcomed. The current work showcases one such strategy by functionalizing the silver nanoparticles with L-fucose to increase their interactions with the LecB lectins present on P. aeruginosa PAO1. The advantage of this approach lies in the higher bactericidal and antibiofilm activity of fucose-functionalized silver nanoparticles (FNPs) as compared to the citrate-capped silver nanoparticles (CNPs) of similar size and concns. The superior bactericidal potential of FNPs as demonstrated by fluorescence-assisted cell sorting, confocal laser scanning microscopy, and transmission electron microscopy analyses may be attributed to the higher reactive oxygen species generation and oxidative membrane damage. Addnl., FNPs prevented the formation of biofilms by downregulating the expression of various virulence genes at lower concns. as compared to CNPs. The practical applicability of the approach was demonstrated by preventing bacterial colonization on artificial silicone rubber surfaces. These results can be extrapolated in the treatment of catheter-assocd. urinary tract infections caused by P. aeruginosa. In conclusion, the present work strongly advocates the use of antivirulence targets and their corresponding binding residues for the augmentation of the bactericidal effect of silver nanoparticles.
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    Rai, M. K.; Deshmukh, S. D.; Ingle, A. P.; Gade, A. K. Silver Nanoparticles: the Powerful Nanoweapon Against Multidrug-Resistant Bacteria. J. Appl. Microbiol. 2012, 112, 841– 852,  DOI: 10.1111/j.1365-2672.2012.05253.x
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    Silver nanoparticles: the powerful nanoweapon against multidrug-resistant bacteria
    Rai, M. K.; Deshmukh, S. D.; Ingle, A. P.; Gade, A. K.
    Journal of Applied Microbiology (2012), 112 (5), 841-852CODEN: JAMIFK; ISSN:1364-5072. (Wiley-Blackwell)
    In the present scenario, pharmaceutical and biomedical sectors are facing the challenges of continuous increase in the multidrug-resistant (MDR) human pathogenic microbes. Re-emergence of MDR microbes is facilitated by drug and/or antibiotic resistance, which is acquired way of microbes for their survival and multiplication in uncomfortable environments. MDR bacterial infections lead to significant increase in mortality, morbidity and cost of prolonged treatments. Therefore, development, modification or searching the antimicrobial compds. having bactericidal potential against MDR bacteria is a priority area of research. Silver in the form of various compds. and bhasmas have been used in Ayurveda to treat several bacterial infections since time immemorial. As several pathogenic bacteria are developing antibiotic resistance, silver nanoparticles are the new hope to treat them. This review discusses the bactericidal potential of silver nanoparticles against the MDR bacteria. This multiactional nanoweapon can be used for the treatment and prevention of drug-resistant microbes.
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    Xie, X.; Sun, T.; Xue, J.; Miao, Z.; Yan, X.; Fang, W.; Li, Q.; Tang, R.; Lu, Y.; Tang, L.; Zha, Z.; He, T. Ag Nanoparticles Cluster with pH-Triggered Reassembly in Targeting Antimicrobial Applications. Adv. Funct. Mater. 2020, 30, 2000511,  DOI: 10.1002/adfm.202000511
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    Ag nanoparticles cluster with pH-triggered reassembly in targeting antimicrobial applications
    Xie, Xianli; Sun, Tian Ci; Xue, Jingzhe; Miao, Zhaohua; Yan, Xu; Fang, Wei Wei; Li, Qing; Tang, Rupei; Lu, Yang; Tang, Longxiang; Zha, Zhengbao; He, Tao
    Advanced Functional Materials (2020), 30 (17), 2000511CODEN: AFMDC6; ISSN:1616-301X. (Wiley-VCH Verlag GmbH & Co. KGaA)
    Antibacterial efficiency can be effectively improved by applying targeting antibacterial materials and strategies. Herein, the successful synthesis of uniform pH-responsive Ag nanoparticle clusters (AgNCs) is demonstrated, which can collapse and reassemble into nonuniform Ag NPs upon exposure to the acidic microenvironment of bacterial infections. This pH triggered reassembly contributes greatly to the improved antibacterial activities of AgNCs against both methicillin-resistant Staphylococcus aureus (MRSA) and Escherichia coli (E. coli). The min. inhibitory concn. and min. bactericidal concn. against MRSA are as low as 4 and 32 μg mL-1 (which are 8 and 32 μg mL-1 for E. coli), resp. In vivo skin wound healing expts. confirm AgNCs can serve as an effective wound dressing to accelerate the healing of MRSA infection. The development of responsive AgNCs offers new materials and strategies in targeting antibacterial applications.
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    Tran, H. A.; Tran, P. A. In Situ Coatings of Silver Nanoparticles for Biofilm Treatment in Implant-Retention Surgeries: Antimicrobial Activities in Monoculture and Coculture. ACS Appl. Mater. Interfaces 2021, 13, 41435– 41444,  DOI: 10.1021/acsami.1c08239
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    In Situ Coatings of Silver Nanoparticles for Biofilm Treatment in Implant-Retention Surgeries: Antimicrobial Activities in Monoculture and Coculture
    Tran, Hien A.; Tran, Phong A.
    ACS Applied Materials & Interfaces (2021), 13 (35), 41435-41444CODEN: AAMICK; ISSN:1944-8244. (American Chemical Society)
    Bacterial biofilms are indicated in most medical device-assocd. infections. Treating these biofilms is challenging yet critically important for applications such as in device-retention surgeries, which can have reinfection rates of up to 80%. This in vitro study centered around our new method of treating biofilm and preventing reinfection. Ionic silver (Ag, in the form of silver nitrate) combined with dopamine and a biofilm-lysing enzyme (α-amylase) were applied to model 4-day-old Staphylococcus aureus biofilms on titanium substrates to degrade the extracellular matrix of the biofilm and kill the biofilm bacteria. In this process, the oxidative self-polymn. of dopamine converted Ag ions into Ag nanoparticles that, together with the resultant self-adhering polydopamine (PDA), formed coatings that strongly bound to the treated substrates. Surprisingly, although these Ag/PDA coatings significantly reduced S. aureus growth in std. bacterial monoculture, they showed much lower antimicrobial activity in coculture of the bacteria and osteoblastic MC3T3-E1 cells in which the bacteria were also found attached to the osteoblasts. This S. aureus- osteoblast interaction was also linked to bacterial survival against gentamicin treatment obsd. in coculture. Our study thus provided clear evidence suggesting that bacteria's interactions with tissue cells surrounding implants may significantly contribute to their resistance to antimicrobial treatment.
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    Morones, J. R.; Elechiguerra, J. L.; Camacho, A.; Holt, K.; Kouri, J. B.; Ramírez, J. T.; Yacaman, M. J. The Bactericidal Effect of Silver Nanoparticles. Nanotechnology 2005, 16, 2346– 2353,  DOI: 10.1088/0957-4484/16/10/059
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    The bactericidal effect of silver nanoparticles
    Morones, Jose Ruben; Elechiguerra, Jose Luis; Camacho, Alejandra; Holt, Katherine; Kouri, Juan B.; Ramirez, Jose Tapia; Yacaman, Miguel Jose
    Nanotechnology (2005), 16 (10), 2346-2353CODEN: NNOTER; ISSN:0957-4484. (Institute of Physics Publishing)
    Nanotechnol. is expected to open new avenues to fight and prevent disease using at. scale tailoring of materials. Among the most promising nanomaterials with antibacterial properties are metallic nanoparticles, which exhibit increased chem. activity due to their large surface to vol. ratios and crystallog. surface structure. The study of bactericidal nanomaterials is particularly timely considering the recent increase of new resistant strains of bacteria to the most potent antibiotics. This has promoted research in the well known activity of silver ions and silver-based compds., including silver nanoparticles. The present work studies the effect of silver nanoparticles in the range of 1-100 nm on Gram-neg. bacteria using high angle annular dark field (HAADF) scanning TEM (STEM). Our results indicate that the bactericidal properties of the nanoparticles are size dependent, since the only nanoparticles that present a direct interaction with the bacteria preferentially have a diam. of ∼1-10 nm.
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    Matsumura, Y.; Yoshikata, K.; Kunisaki, S.-i.; Tsuchido, T. Mode of Bactericidal Action of Silver Zeolite and its Comparison with that of Silver Nitrate. Appl. Environ. Microbiol. 2003, 69, 4278– 4281,  DOI: 10.1128/aem.69.7.4278-4281.2003
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    Mode of bactericidal action of silver zeolite and its comparison with that of silver nitrate
    Matsumura, Yoshinobu; Yoshikata, Kuniaki; Kunisaki, Shin-ichi; Tsuchido, Tetsuaki
    Applied and Environmental Microbiology (2003), 69 (7), 4278-4281CODEN: AEMIDF; ISSN:0099-2240. (American Society for Microbiology)
    The properties of the bactericidal action of silver zeolite as affected by inorg. salts and ion chelators were similar to those of silver nitrate. The results suggest that the contact of the bacterial cell with silver zeolite, the consequent transfer of silver ion to the cell, and the generation of reactive oxygen species in the cell are involved in the bactericidal activity of silver zeolite.
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    Gupta, A.; Maynes, M.; Silver, S. Effects of Halides on Plasmid-mediated Silver Resistance in Escherichia Coli. Appl. Environ. Microbiol. 1998, 64, 5042– 5045,  DOI: 10.1128/aem.64.12.5042-5045.1998
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    Effects of halides on plasmid-mediated silver resistance in Escherichia coli
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    Applied and Environmental Microbiology (1998), 64 (12), 5042-5045CODEN: AEMIDF; ISSN:0099-2240. (American Society for Microbiology)
    Silver resistance of sensitive Escherichia coli J53 and resistance plasmid-contg. J53(pMG101) was affected by halides in the growth medium. The effects of halides on Ag+ resistance were measured with AgNO3 and silver sulfadiazine, both on agar and in liq. Low concns. of chloride made the differences in MICs between sensitive and resistant strains larger. High concns. of halides increased the sensitivities of both strains to Ag+.
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    Feng, Q. L.; Wu, J.; Chen, G. Q.; Cui, F. Z.; Kim, T. N.; Kim, J. O. A mechanistic Study of the Antibacterial Effect of Silver Ions on Escherichia coli and Staphylococcus aureus. J. Biomed. Mater. Res. 2000, 52, 662– 668,  DOI: 10.1002/1097-4636(20001215)52:4<662::aid-jbm10>3.0.co;2-3
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    A mechanistic study of the antibacterial effect of silver ions on Escherichia coli and Staphylococcus aureus
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    Journal of Biomedical Materials Research (2000), 52 (4), 662-668CODEN: JBMRBG; ISSN:0021-9304. (John Wiley & Sons, Inc.)
    To investigate the mechanism of inhibition of silver ions on microorganisms, two strains of bacteria, namely Gram-neg. Escherichia coli (E. coli) and Gram-pos. Staphylococcus aureus (S. aureus), were treated with AgNO3 and studied using combined electron microscopy and X-ray microanal. Similar morphol. changes occurred in both E. coli and S. aureus cells after Ag+ treatment. The cytoplasm membrane detached from the cell wall. A remarkable electron-light region appeared in the center of the cells, which contained condensed DNA mols. There are many small electron-dense granules either surrounding the cell wall or depositing inside the cells. The existence of elements of silver and sulfur in the electron-dense granules and cytoplasm detected by X-ray microanal. suggested the antibacterial mechanism of silver: DNA lost its replication ability and the protein became inactivated after Ag+ treatment. The slighter morphol. changes of S. aureus compared with E. coli recommended a defense system of S. aureus against the inhibitory effects of Ag+ ions.
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    Cruz-Romero, M.; Kerry, J. Crop-Based Biodegradable Packaging and its Environmental Implications. CAB Rev. Perspect. Agric. Vet. Sci. Nutr. Nat. Resour. 2008, 3, 1– 25,  DOI: 10.1079/pavsnnr20083074
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    Prakash Maran, J.; Sivakumar, V.; Sridhar, R.; Prince Immanuel, V. Development of Model for Mechanical Properties of Tapioca Starch Based Edible Films. Ind. Crops Prod. 2013, 42, 159– 168,  DOI: 10.1016/j.indcrop.2012.05.011
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    Development of model for mechanical properties of tapioca starch based edible films
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    Industrial Crops and Products (2013), 42 (), 159-168CODEN: ICRDEW; ISSN:0926-6690. (Elsevier B.V.)
    Eco-efficient products are the new generation of bio-based products prepd. with sustainable materials, which agree with ecol. and economic requirements including environmentally acceptable disposal of post-user waste. Increasing environmental concerns assocd. with handling of plastic waste has emphasized the importance of developing biodegradable edible films from starch. The objective of this study is to develop models and study the individual and interactive effects of the process variables on the mech. properties of tapioca starch-based edible films using Box-Behnken design. Box-Behnken design with four factors at three levels was employed to evaluate the individual and interactive effects of process parameters (tapioca starch 1-3 g; glycerol 0.5-1.0 mL; agar 0.5-1.0 g; and span 80: 0.1-0.5 mL) on the tensile strength, elongation, Young's modulus, puncture force, and puncture deformation resp. The results were analyzed using Pareto anal. of variance (ANOVA). For each response, second order polynomial regression models were developed and it showed good fit of the exptl. data with high coeff. of detn. (R 2) and a close agreement between exptl. and predicted values was found. The response surface and contour plots were constructed for representing the relationship between the process parameters and the responses.
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    Siddiqui, J.; Taheri, M.; Alam, A. U.; Deen, M. J. Nanomaterials in Smart Packaging Applications: A Review. Small 2021, 18, 2101171,  DOI: 10.1002/smll.202101171
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    Zhang, Y.; Ma, Q.; Critzer, F.; Davidson, P. M.; Zhong, Q. Physical and Antibacterial Properties of Alginate Films Containing Cinnamon Bark Oil and Soybean Oil. LWT--Food Sci. Technol. 2015, 64, 423– 430,  DOI: 10.1016/j.lwt.2015.05.008
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    Physical and antibacterial properties of alginate films containing cinnamon bark oil and soybean oil
    Zhang, Yue; Ma, Qiumin; Critzer, Faith; Davidson, P. Michael; Zhong, Qixin
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    Edible antimicrobial films with essential oils are potential intervention strategies to improve microbiol. safety of foods. The aim of this work was to study the effects of incorporating soybean oil (SBO) on the phys. and antibacterial properties of alginate films prepd. with 1% or 2% cinnamon bark oil (CBO). The incorporation of SBO improved the microstructure homogeneity and transparency, reduced tensile strength, elongation at break, water soly., and total solids content but had no obvious effects on the water vapor permeability of films. Films prepd. with 1% CBO had a low residual CBO after film formation and storage. For 2% CBO treatments, the addn. of SBO reduced the loss of CBO during storage of films and improved the antimicrobial activity against Escherichia coli O157:H7, Listeria monocytogenes and Salmonella enterica. The results suggest that SBO can be used to improve certain phys. characteristics and the antibacterial efficacy of edible films contg. essential oils.
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    Xia, C.; Wang, L.; Dong, Y.; Zhang, S.; Shi, S. Q.; Cai, L.; Li, J. Soy Protein Isolate-Based Films Cross-Linked by Epoxidized Soybean Oil. RSC Adv. 2015, 5, 82765– 82771,  DOI: 10.1039/c5ra15590h
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    Soy protein isolate-based films cross-linked by epoxidized soybean oil
    Xia, Changlei; Wang, La; Dong, Youming; Zhang, Shifeng; Shi, Sheldon Q.; Cai, Liping; Li, Jianzhang
    RSC Advances (2015), 5 (101), 82765-82771CODEN: RSCACL; ISSN:2046-2069. (Royal Society of Chemistry)
    Epoxidized soybean oil (ESO) is an environmentally friendly crosslinking agent derived from soybean, having multiple epoxy groups in its mols. It can effectively improve tensile strength and water resistance of soy protein isolate (SPI)-based films. The properties of the SPI-based films were characterized by X-ray diffraction and attenuated total reflectance Fourier transform IR spectroscopy. The best performance of the SPI-based films was achieved when the ESO addn. was 2.5%, for which tensile modulus, tensile strength and 10% offset yield strength were increased to 265.0 MPa, 9.8 MPa and 6.8 MPa, resp. Compared to untreated SPI-based films, these were increases of 695.6%, 139.8%, and 246.6%, resp. However, the elongation at break was decreased by 67.6% due to the crosslinking between SPI and ESO. The SPI-based film modified by 5% ESO had the best water-resistance property and reduced the 24 h water absorption from 209.1% to 45.9%, which was a significant decrease of 78.1%.
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    Liang, S.; Wang, L. A Natural Antibacterial-Antioxidant Film from Soy Protein Isolate Incorporated with Cortex Phellodendron Extract. Polymers 2018, 10, 71,  DOI: 10.3390/polym10010071
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    A natural antibacterial-antioxidant film from soy protein isolate incorporated with cortex Phellodendron extract
    Liang, Shumin; Wang, Lijuan
    Polymers (Basel, Switzerland) (2018), 10 (1), 71/1-71/13CODEN: POLYCK; ISSN:2073-4360. (MDPI AG)
    An active film was prepd. by incorporating cortex Phellodendron ext. (CPE, an active agent) into a soybean protein isolate (SPI). Different concns. of CPE (0%, 10%, 12.5%, 15%, 17.5%, 20%, or 22.5%, wt./wt., based on SPI) were mixed into the films characterized by Fourier transform IR spectroscopy, X-ray diffraction, SEM, thermogravimetry, tensile tests, and barrier properties. The rheol. properties of the solns. were also tested. The effects of the CPE content on the antibacterial and antioxidant activities of the films were examd. The results indicated that new hydrogen bonds formed between mols. in the films, and the crystallinity of the films decreased. The incorporation of CPE had no significant influence on the thermal stability of the films. Films contg. 15% CPE had the max. tensile strength of 6.00 MPa. The barrier properties against water vapor, oxygen, and light enhanced with the incorporation of CPE. The antioxidant activity of the SPI film was also improved. The films were effective against Staphylococcus aureus (S. aureus, Gram-pos. bacteria). These results suggest that the SPI/CPE film can potentially extend the shelf lives of foods.
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    Podshivalov, A.; Zakharova, M.; Glazacheva, E.; Uspenskaya, M. Gelatin/Potato Starch Edible Biocomposite Films: Correlation Between Morphology and Physical Properties. Carbohydr. Polym. 2017, 157, 1162– 1172,  DOI: 10.1016/j.carbpol.2016.10.079
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    Gelatin/potato starch edible biocomposite films: Correlation between morphology and physical properties
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    Carbohydrate Polymers (2017), 157 (), 1162-1172CODEN: CAPOD8; ISSN:0144-8617. (Elsevier Ltd.)
    The paper presents the results of studies of the microstructure morphol. and the operational properties of the gelatin/potato starch/glycerol edible biocomposite films varying in the starch content from 0 to 50 wt% prepd. by casting film-forming soln. and dying at 36 °C for 15 h. The biocomposite films were shown phase sepd. heterogeneous morphol. with the gelatin matrix as a continuous phase and microgranules of starch as a minor phase. It is found that when the starch content ≤ 30 wt% the phase sepn. mechanism is nucleation and grow, whereas the starch content > 30 wt% then the spinodal decompn. is the dominant mechanism. The work focuses on findings the influence of the phase sepn. mechanisms on the size of starch granules during the drying process, as well as the impact of these mechanisms on optical, frictional, mech., thermal and water-barrier properties.
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    Mukhopadhyay, R.; Sree, K. D.; Saneeha, R.; Kale, P.; Iram, U. Preparation and Characterization of Biodegradable Plastics out of Food Wastes as Prospective and Eco-Friendly Medical Devices. Int. J. Res. Appl. Sci. Eng. Technol. 2017, 5, 134– 142
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    Striving to achieve cost-competitive biomass-derived materials for the plastics industry, the incorporation of starch (corn and potato) to a base formulation of albumen and glycerol was considered. To study the effects of formulation and processing, albumen/starch-based bioplastics contg. 0-30 wt.% starch were prepd. by thermo-plastic and thermo-mech. processing. Transmittance measurements, DSC, DMTA and tensile tests were performed on the resulting bioplastics. Optical and tensile properties were strongly affected by starch concn. However, DMTA at low deformation proved to be insensitive to starch addn. Thermo-mech. processing led to transparent albumen/starch materials with values of strength at low deformation comparable to commodity plastics. Consequently, albumen biopolymers may become a biodegradable alternative to oil-derived plastics for manufg. transparent packaging and other plastic stuffs.
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    Abdullah, A. H. D.; Pudjiraharti, S.; Karina, M.; Putri, O. D.; Fauziyyah, R. H. Fabrication and Characterization of Sweet Potato Starch-Based Bioplastics Plasticized with Glycerol. J. Biol. Sci. 2019, 19, 57– 64,  DOI: 10.3923/jbs.2019.57.64
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    Fabrication and characterization of sweet potato starch-based bioplastics plasticized with glycerol
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    Journal of Biological Sciences (Faisalabad, Pakistan) (2019), 19 (1), 57-64CODEN: JBSFA9; ISSN:1727-3048. (Asian Network for Scientific Information)
    Background and Objective: Poor biodegradability and the contamination risk of petrochem.-based plastics encouraged the utilization of renewable resources to replace them due to their inexpensive, renewable, biodegradable and compostable properties. This study aimed to investigate the utilization of sweet potato sourced from Indonesia as a base material of bioplastic and its characteristics for food packaging application. Materials and Methods: Starch was extd. from sweet potato and bioplastics was prepd. by mixing starch with glycerol using different starch:glycerol wt./wt. ratio (2.5:1, 2.75:1, 3:1 and 3.5:1). Intermol. interactions and microstructure of bioplastics were assessed by using FTIR and SEM, resp. The phys. and mech. properties were evaluated by measuring the d., tensile strength and elongation at break. The relative hydrophobicity was examd. by measuring the water contact angle. The biodegradability was also investigated with the aid of enzymic degrdn. by microbes. Results: Microstructure of bioplastics showed the incomplete gelatinization with the increase of starch:glycerol ratio indicated by the visible inhomogeneous granules. FTIR spectra exhibited that the intermol. interaction in bioplastics occurred through C-O-H, O-H, C-H aliph. and C=O groups. Mech. properties evaluation showed that bioplastic with 3.5:1 (starch:glycerol) ratio exhibited the highest tensile strength of 2.57 MPa with the lowest elongation of 6.27%. Bioplastic with 3.5:1 (starch:glycerol) ratio also showed the highest d. and contact angle of 1.66 g cm-3 and 50.1 °, resp. The fastest enzymic degrdn. showed by the highest microbial growth was presented by bioplastic with 3.5:1 (starch:glycerol) ratio as well. Conclusion: Bioplastic with the highest sweet potato starch:glycerol ratio showed the most excellent phys., mech. and biodegradability properties.
  52. 52
    Gong, H.-Y.; Rambo, B. M.; Karnas, E.; Lynch, V. M.; Keller, K. M.; Sessler, J. L. Environmentally Responsive Threading, Dethreading, and Fixation of Anion-Induced Pseudorotaxanes. J. Am. Chem. Soc. 2011, 133, 1526– 1533,  DOI: 10.1021/ja109102k
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    Environmentally Responsive Threading, Dethreading, and Fixation of Anion-Induced Pseudorotaxanes
    Gong, Han-Yuan; Rambo, Brett M.; Karnas, Elizabeth; Lynch, Vincent M.; Keller, Karin M.; Sessler, Jonathan L.
    Journal of the American Chemical Society (2011), 133 (5), 1526-1533CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)
    The tetracationic macrocycle cyclo[2](2,6-di(1H-imidazol-1-yl)pyridine)[2](1,4-dimethylenebenzene) hexafluorophosphate (14+·4PF6-) acts as a large, flexible "mol. box" that supports the formation of environmentally responsive anion-induced pseudorotaxanes, as well as other extended structures, including metal-linked supramol. polyrotaxanes. Specifically, the combination of the tetracation 14+ and bis-carboxylate guests derived from 4,4'-biphenyldicarboxylic acid and 2,6-naphthalenedicarboxylic acid results in the formation of pseudorotaxanes that respond to changes in environmental stimuli, including pH and temp. The resulting structures can be "locked into place" via the addn. of a metal-linker in the form of Ag(I); this gives rise to an ordered metal-linked polyrotaxane. The interpenetrated constructs described in this article were characterized in soln. and in the solid state by one- and two-dimensional (1H and NOESY) NMR spectroscopy, as well as by mass spectrometry (ESI-MS) and single-crystal X-ray diffraction methods.
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    Wang, H.; Wan, C.-Q.; Yang, J.; Mak, T. C. W. Ligation Behavior of an Oligo-α-sulfanylpyrazinyl Ligand in Silver(I) Complexes Containing Carboxylates. Cryst. Growth Des. 2014, 14, 3530– 3540,  DOI: 10.1021/cg500474j
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    Ligation Behavior of an Oligo-α-sulfanylpyrazinyl Ligand in Silver(I) Complexes Containing Carboxylates
    Wang, Han; Wan, Chong-Qing; Yang, Jin; Mak, Thomas C. W.
    Crystal Growth & Design (2014), 14 (7), 3530-3540CODEN: CGDEFU; ISSN:1528-7483. (American Chemical Society)
    Seven new Ag(I) complexes based on conformationally flexible 2,6-bis(pyrazin-2-ylthio)pyrazine (L) and selected carboxylate ligands, Ag2(L)2(L1)2 (1), [Ag(L)(L2)]∞ (2), [Ag2(L)(L3)2]∞ (3), [Ag2(L)(L4)2]∞ (4), {[Ag2(L)(L5)]· 4H2O}∞ (5), {[Ag2(L)(L6)]· 3H2O}∞ (6), and {[Ag2(L)2(L7)]· 3H2O}∞ (7) (L1 = trifluoroacetate, L2 = heptafluorobutanoate, L3 = 4-cyanobenzoate, L4 = 2-(perfluorophenoxy)acetate, L5 = 1,1'-biphenyl-4,4'-dicarboxylate, L6 = 2,2'-(1,4-phenylene)diacetate, and L7 = naphthalene-2,6-dicarboxylate), have been synthesized and structurally characterized by single-crystal x-ray diffraction analyses. In 1-7, an argentophilic Ag2 dimer is a dominant subunit, which is stabilized by a pair of bridging carboxylate groups. Complexes 1-4 are assembled with monocarboxylates, L, and Ag(I) ions. Complex 1 exists as a discrete dimeric mol., being stabilized by trans pairs of L and L1. Co-crystn. of discrete mols. and infinite chains occur in complex 2. In 3 and 4, Ag2 dimers are linked by ligands L to furnish a double-bridged chain and a ladder-like structure, resp. Complexes 5-7 are assembled with dicarboxylate spacers and flexible L, which link Ag2 units to form a 2D slablike architecture in 5, and 3D coordination frameworks in 6 and 7. In addn., the effect of the carboxylate ligands on the ligation behavior of L and supramol. assembly of the series of compds. are discussed.
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    Fangfang, Z.; Xinpeng, B.; Wei, G.; Wang, G.; Shi, Z.; Jun, C. Effects of Virgin Coconut Oil on the Physicochemical, Morphological and Antibacterial Properties of Potato Starch-Based Biodegradable Films. Int. J. Food Sci. 2020, 55, 192– 200,  DOI: 10.1111/ijfs.14262
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    Effects of virgin coconut oil on the physicochemical, morphological and antibacterial properties of potato starch-based biodegradable films
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    International Journal of Food Science and Technology (2020), 55 (1), 192-200CODEN: IJFTEZ; ISSN:0950-5423. (Wiley-Blackwell)
    Summary : This study investigated the effects of adding different concns. of virgin coconut oil (VCO) on the optical, mech., thermodn. and antimicrobial properties, as well as water vapor permeability and morphol. of potato starch-based biodegradable films. Increasing VCO concns. caused a rise in the light transmittance of the films from 2.13 to 4.79 mm-1 and a decrease in water vapor transmittance from 6.77 to 2.12 (10-5 GPa-1 h-1 m-1). At a VCO concn. of 14 wt% (based on potato starch), the tensile strength reached its highest value (19.98 MPa). SEM showed that the surface of the film became smoother as VCO concn. increased. The addn. of VCO inhibited the growth of Listeria monocytogenes, Staphylococcus aureus and Escherichia coli. In conclusion, VCO supplementation improved the mech., antibacterial and water barrier properties of starch-based films. These results could expand the scope of the application of starch-based films in food packaging.
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    Altayan, M. M.; Al Darouich, T.; Karabet, F. On the Plasticization Process of Potato Starch: Preparation and Characterization. Food Biophys. 2017, 12, 397– 403,  DOI: 10.1007/s11483-017-9495-2
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    Antimicrobial Agents and Chemotherapy (2010), 54 (10), 4208-4218CODEN: AMACCQ; ISSN:0066-4804. (American Society for Microbiology)
    Prosthetic joint replacements are used increasingly to alleviate pain and improve mobility of the progressively older and more obese population. Implant infection occurs in about 5% of patients and entails significant morbidity and high social costs. It is most often caused by staphylococci, which are introduced perioperatively. They are a source of prolonged seeding and difficult to treat due to antibiotic resistance; therefore, infection prevention by prosthesis coating with nonantibiotic-type anti-infective substances is indicated. A renewed interest in topically used silver has fostered development of silver nanoparticles, which, however, present a potential health hazard. Here we present new silver coordination polymer networks with tailored phys. and chem. properties as nanostructured coatings on metallic implant substrates. These compds. exhibited strong biofilm sugar-independent bactericidal activity on in vitro-grown biofilms and prevented murine Staphylococcus epidermidis implant infection in vivo with slow release of silver ions and limited transient leukocyte cytotoxicity. Furthermore, we describe the biochem. and mol. mechanisms of silver ion action by gene screening and by targeting cell metab. of S. epidermidis at different levels. We demonstrate that silver ions inactivate enzymes by binding sulfhydryl (thiol) groups in amino acids and promote the release of iron with subsequent hydroxyl radical formation by an indirect mechanism likely mediated by reactive oxygen species. This is the first report investigating the global metabolic effects of silver in the context of a therapeutic application. We anticipate that the compds. presented here open a new treatment field with a high medical impact.
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    Herein, antibacterial coordination polymer hydrogels were conveniently fabricated in water via coordination between silver nitrate and PEGylated bisimidazolylbenzyl alc. (1a-c). These coordination polymer hydrogels exhibit much better antibacterial activity than silver nitrate against both Gram-neg. and Gram-pos. pathogens including multidrug-resistant pathogens. The coordination polymer Ag/1c with a long PEG chain (PEG1000) was demonstrated to be the most effective antibacterial material, and its min. inhibition concns. (MICs) could be as low as 15.2 times for common Staphylococcus aureus and 4.8 times for methicillin-resistant Staphylococcus aureus over that of silver nitrate. With improved antibacterial performance, easy prepn. method, improved stability, sustained releasability, outstanding ductility and low cytotoxicity, the as-prepd. coordination polymer hydrogels should find various potential applications such as in clin. burn and wound dressings, biofilms, bioadhesives, and coatings of biomedical materials.

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  • Abstract

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    Figure 1

    Figure 1. Preparation of bioCP-doped [SBO]n and [PS]n biopolymer films.

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    Figure 2

    Figure 2. Sample coupons for (a) [SBO]n and (b) [PS]n biopolymer films.

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    Figure 3

    Figure 3. Structural fragments of [Ag2(μ6-hfa)]n (1). (a) Coordination mode of μ6-hfa2– ligand. (b) Coordination environment of silver atoms including argentophilic interactions (dotted cyan lines). (c,d) Front (c) and side (d) view of 2D double layer. Further details: (a–d) Ag (cyan), C (gray), and O (red); views along the c (c) and a (d) axes.

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    Figure 4

    Figure 4. Structural fragments of [Ag2(μ4-nda)(H2O)2]n (2). (a) Coordination mode of μ4-nda2– ligand and environment of Ag1 centers; weaker argentophilic Ag···Ag and Ag···O interactions are shown as dotted lines. (b) 2D supramolecular layer. Further details: Ag (cyan), C (gray), and O (red); (b) view along the c axis.

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    Figure 5

    Figure 5. Morphological characterization of [SBO]n and [PS]n films by SEM–EDX. SEM images: (a) SBO film; (b) 1-0.5%@[SBO]n; (c) 1-0.5%@[SBO]n [the same region as (b)] with EDX analysis of Ag distribution; (d) 2-0.5%@[SBO]n, where bioCP particles can be seen throughout the material; (e) 2-0.5%@[SBO]n with EDX analysis of Ag distribution; (f) 2-0.5%@[SBO]n (the same region as e) with EDX analysis of O distribution; (g) [PS]n film; (h) 1-0.5%@[PS]n, where bioCP particles can be seen throughout the material; (i) 1-0.5%@[PS]n (the same region as h) with EDX analysis of Ag distribution. Images (a), (d), (i), and (h) were obtained at 1000× magnification and (b,c,e,f,i) at 500× magnification.

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    Figure 6

    Figure 6. (a) Minimum inhibition radius (mean ± SD) showing the normalized activity of 1 and 2 against P. aeruginosa and E. coli (Gram-negative) and S. aureus and S. epidermidis (Gram-positive) bacteria. (b) Examples of the obtained halos representing bacterial growth inhibition.

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    Figure 7

    Figure 7. Normalized activity of [SBO]n biopolymer films containing varying concentrations of Ag2O (Ag2O@[SBO]n) and compounds 1 (1@[SBO]n) and 2 (2@[SBO]n) against P. aeruginosa and E. coli (Gram-negative) and S. aureus and S. epidermidis (Gram-positive) bacteria.

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    Figure 8

    Figure 8. Normalized activity of [SBO]nvs [PS]n biopolymer films containing 0.5% of Ag2O and compounds 1 and 2 against P. aeruginosa and E. coli (Gram-negative) and S. aureus and S. epidermidis (Gram-positive) bacteria. Significant statistical differences were found using the two-way ANOVA and subsequent Bonferroni’s multiple comparisons test with 95% confidence interval, represented as *P ≤ 0.05; **P ≤ 0.01; and ***P ≤ 0.001.

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    Figure 9

    Figure 9. Normalized biofilm inhibition activity of [SBO]n biopolymer films containing varying concentration of Ag2O (Ag2O@[SBO]n) and compounds 1 (1@[SBO]n) and 2 (2@[SBO]n), against P. aeruginosa and E. coli (Gram-negative) and S. aureus and S. epidermidis (Gram-positive) bacteria. Significant statistical differences were found using the two-way ANOVA and subsequent Bonferroni’s multiple comparisons test with 95% confidence interval, represented as *P ≤ 0.05; **P ≤ 0.01; and ***P ≤ 0.001.

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    Figure 10

    Figure 10. Normalized biofilm inhibition activity of [SBO]nvs [PS]n biopolymer films doped with 0.5% of Ag2O and compounds 1 and 2 against P. aeruginosa and E. coli (Gram-negative) and S. aureus and S. epidermidis (Gram-positive) bacteria. Significant statistical differences were found using the two-way ANOVA and subsequent Bonferroni’s multiple comparisons test with 95% confidence interval, represented as *P ≤ 0.05; **P ≤ 0.01; and ***P ≤ 0.001.

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      Wu, Shuangmei; Xu, Chen; Zhu, Yiwen; Zheng, Liang; Zhang, Ludan; Hu, Yang; Yu, Bingran; Wang, Yuguang; Xu, Fu-Jian
      Advanced Functional Materials (2021), 31 (33), 2103591CODEN: AFMDC6; ISSN:1616-301X. (Wiley-VCH Verlag GmbH & Co. KGaA)
      Efficient antimicrobials are urgently needed for the treatment of bacterial biofilms due to their resistance to traditional drugs. Photodynamic therapy (PDT) is a new strategy that has been used to combat bacteria and biofilms. Cationic photosensitizers, particularly cationic photodynamic nanoagents, are usually chosen to enhance photodynamic antimicrobial activity. However, pos. charged nanoparticles (NPs) are beneficial to cellular internalization, which causes increased cell cytotoxicity. Herein, a pH-sensitive photodynamic nanosystem is designed. Rose Bengal (RB) polydopamine (PDA) NPs are decorated in a layer-by-layer fashion with polymyxin B (PMB) and gluconic acid (GA) to generate functionally adaptive NPs (RB@PMB@GA NPs). RB@PMB@GA NPs remain neg. at physiol. pH and exhibit good biocompatibility. When RB@PMB@GA NPs are exposed to an acidic infectious environment, the surface charge of the NPs is, in turn, pos. charged as a result of pH-sensitive electrostatic interactions. This surface charge conversion allows the RB@PMB@GA to effectively bind to the surfaces of bacteria and enhance photoinactivation efficiency against gram-neg. bacteria. Most importantly, RB@PMB@GA NPs exhibit good biofilm penetration and eradication under acidic conditions. Furthermore, RB@PMB@GA NPs efficiently eliminate biofilm infections in vivo. This study provides a promising strategy for safely treating biofilm-assocd. infections in vivo.
    6. 6
      Sharma, D.; Misba, L.; Khan, A. U. Antibiotics Versus Biofilm: an Emerging Battleground in Microbial Communities. Antimicrob. Resist. Infect. Control 2019, 8, 76,  DOI: 10.1186/s13756-019-0533-3
      6
      Antibiotics versus biofilm: an emerging battleground in microbial communities
      Sharma Divakar; Misba Lama; Khan Asad U
      Antimicrobial resistance and infection control (2019), 8 (), 76 ISSN:.
      Biofilm is a complex structure of microbiome having different bacterial colonies or single type of cells in a group; adhere to the surface. These cells are embedded in extracellular polymeric substances, a matrix which is generally composed of eDNA, proteins and polysaccharides, showed high resistance to antibiotics. It is one of the major causes of infection persistence especially in nosocomial settings through indwelling devices. Quorum sensing plays an important role in regulating the biofilm formation. There are many approaches being used to control infections by suppressing its formation but CRISPR-CAS (gene editing technique) and photo dynamic therapy (PDT) are proposed to be used as therapeutic approaches to subside bacterial biofim infections, especially caused by deadly drug resistant bad bugs.
    7. 7
      Jorge, P.; Magalhães, A. P.; Grainha, T.; Alves, D.; Sousa, A. M.; Lopes, S. P.; Pereira, M. O. Antimicrobial Resistance Three Ways: Healthcare Crisis, Major Concepts and the Relevance of Biofilms. FEMS Microbiol. Ecol. 2019, 95, fiz115,  DOI: 10.1093/femsec/fiz115
      There is no corresponding record for this reference.
    8. 8
      Şen Karaman, D.; Ercan, U. K.; Bakay, E.; Topaloğlu, N.; Rosenholm, J. M. Evolving Technologies and Strategies for Combating Antibacterial Resistance in the Advent of the Postantibiotic Era. Adv. Funct. Mater. 2020, 30, 1908783,  DOI: 10.1002/adfm.201908783
      8
      Evolving technologies and strategies for combating antibacterial resistance in the advent of the postantibiotic Era
      Sen Karaman, Didem; Ercan, Utku Kuersat; Bakay, Emel; Topaloglu, Nermin; Rosenholm, Jessica M.
      Advanced Functional Materials (2020), 30 (15), 1908783CODEN: AFMDC6; ISSN:1616-301X. (Wiley-VCH Verlag GmbH & Co. KGaA)
      A review. The threats posed by the impending "postantibiotic era" have put forward urgent challenges to be overcome by providing new diagnostic and therapeutic regimes for improved diagnosis and treatment of bacterial infections. Antibiotic resistance and incurable bacterial infections are esp. important in a society faced with rapid demog. changes. With very few new antibiotics in the drug development pipeline, not being able to match the pace of antimicrobial resistance evolution, developments within other fields such as materials sciences and medical technologies are required to realize innovative antibacterial approaches. This progress report presents recent advances in esp. nanotechnol.-based approaches and their concomitant use with complementary antibacterial treatments. Synergistically improved antibacterial activity can be reached by considering novel, promising approaches such as photodynamic and photothermal therapy as well as cold atm. pressure treatments as complementary strategies to fight against antibacterial resistance. Moreover, this report describes how these novel technologies can be further improved esp. by integration of nanomaterials into the currently applied single modal strategies against bacterial infections.
    9. 9
      Friedlander, A.; Nir, S.; Reches, M.; Shemesh, M. Preventing Biofilm Formation by Dairy-Associated Bacteria Using Peptide-Coated Surfaces. Front. Microbiol. 2019, 10, 1405,  DOI: 10.3389/fmicb.2019.01405
      9
      Preventing Biofilm Formation by Dairy-Associated Bacteria Using Peptide-Coated Surfaces
      Friedlander Alon; Shemesh Moshe; Friedlander Alon; Nir Sivan; Reches Meital
      Frontiers in microbiology (2019), 10 (), 1405 ISSN:1664-302X.
      Biofilm-forming bacteria, which colonize the surfaces of equipment in the dairy industry, may adversely affect the safety and quality of the milk and its products. Despite numerous efforts to combat biofilm formation, there is still no effective technological means to thoroughly solve the biofilm problem in the dairy industry. Here, we introduced peptide-based coating in order to modify the physical properties of the stainless steel surface by affecting its availability for bacterial adhesion. We found that the coated surface displays a notable decrease in the ability of bacterial cells to attach and to subsequently form biofilm by Gram-positive Bacillus licheniformis and Gram-negative Pseudomonas aeruginosa. Furthermore, the coated surface retained its anti-biofilm ability following its exposure to raw milk. Importantly, the modified surface did not affect the milk coagulation process or its nutritious properties and quality. Overall, this anti-biofilm approach may serve as an attractive solution for the dairy industry in its struggle against bacterial contamination.
    10. 10
      Li, X.; Wu, B.; Chen, H.; Nan, K.; Jin, Y.; Sun, L.; Wang, B. Recent Developments in Smart Antibacterial Surfaces to Inhibit Biofilm Formation And Bacterial Infections. J. Mater. Chem. B 2018, 6, 4274– 4292,  DOI: 10.1039/c8tb01245h
      10
      Recent developments in smart antibacterial surfaces to inhibit biofilm formation and bacterial infections
      Li, Xi; Wu, Biao; Chen, Hao; Nan, Kaihui; Jin, Yingying; Sun, Lin; Wang, Bailiang
      Journal of Materials Chemistry B: Materials for Biology and Medicine (2018), 6 (26), 4274-4292CODEN: JMCBDV; ISSN:2050-7518. (Royal Society of Chemistry)
      Since their development over 70 years, antibiotics are still the most effective strategy to treat bacterial biofilms and infections. However, the overuse of antibiotics in human healthcare and industrial applications has resulted in the development of serious antibiotic-resistant bacteria. Therefore, alternative ways to prevent bacteria attachment and biofilm formation are urgently needed. Recently, mediated biofilm formation processes and smart antibacterial surfaces have emerged as promising strategies to prevent and treat bacterial infections. This review discusses the recent progress in biofilm interference and smart antibacterial surfaces. Smart antibacterial and anti-biofilm surfaces should be responsive to the bacterial infection environment, switchable between various antibacterial functions and have a special bio-inspired structure and function. The major topics discussed are: (i) smart anti-biofilm surfaces via the prevention of biofilm formation or promoting mature biofilm dissoln., (ii) smart materials for reversible killing and/or release of bacteria, (iii) smart surfaces responsive to bacterial infection microenvironments or external stimuli and (iv) bio-inspired surfaces with antifouling and bactericidal properties.
    11. 11
      Ivanova, A.; Ivanova, K.; Tied, A.; Heinze, T.; Tzanov, T. Layer-By-Layer Coating of Aminocellulose and Quorum Quenching Acylase on Silver Nanoparticles Synergistically Eradicate Bacteria and Their Biofilms. Adv. Funct. Mater. 2020, 30, 2001284,  DOI: 10.1002/adfm.202001284
      11
      Layer-By-Layer Coating of Aminocellulose and Quorum Quenching Acylase on Silver Nanoparticles Synergistically Eradicate Bacteria and Their Biofilms
      Ivanova, Aleksandra; Ivanova, Kristina; Tied, Antje; Heinze, Thomas; Tzanov, Tzanko
      Advanced Functional Materials (2020), 30 (24), 2001284CODEN: AFMDC6; ISSN:1616-301X. (Wiley-VCH Verlag GmbH & Co. KGaA)
      The emergence of antibiotic-resistant bacteria and the failure of the existing antibacterial therapeutics call for development of novel treatment strategies. Furthermore, the formation of bacterial biofilms restricts drug penetration and efficiency, causing life-threatening infections. Bacterial attachment and biofilm formation are regulated by the cell-to-cell communication phenomenon called quorum sensing (QS). In this work, antimicrobial silver nanoparticles (AgNPs) are decorated in a layer-by-layer fashion with the oppositely charged aminocellulose (AM) and acylase to generate hybrid nanoentities with enhanced antibacterial and antibiofilm activities as well as reduced cytotoxicity. Acylase, a quorum-quenching enzyme that degrades the QS signals in the extracellular environment of bacteria, disrupts the bacterial QS process and together with the bactericidal AM synergistically lowers fourfold the min. inhibitory concn. of the AgNPs templates toward Gram-neg. Pseudomonas aeruginosa (P. aeruginosa). The hybrid nanoparticles in eightfold-lower concn. than the AgNPs inhibit 45% of the QS-regulated virulence factors produced by the reporter Chromobacterium violaceum bacterial strain and reduce by 100% the P. aeruginosa biofilm formation. Moreover, the sequential deposition of antibacterial/antibiofilm active and biocompatible biopolymers onto the AgNPs allows the engineering of safe nanomaterials that do not affect the viability of human cells.
    12. 12
      Neufeld, B. H.; Neufeld, M. J.; Lutzke, A.; Schweickart, S. M.; Reynolds, M. M. Metal-Organic Framework Material Inhibits Biofilm Formation of Pseudomonas aeruginosa. Adv. Funct. Mater. 2017, 27, 1702255,  DOI: 10.1002/adfm.201702255
      There is no corresponding record for this reference.
    13. 13
      Zhuang, W.; Yuan, D.; Li, J.-R.; Luo, Z.; Zhou, H.-C.; Bashir, S.; Liu, J. Highly Potent Bactericidal Activity of Porous Metal-Organic Frameworks. Adv. Healthcare Mater. 2012, 1, 225– 238,  DOI: 10.1002/adhm.201100043
      13
      Highly potent bactericidal activity of porous metal-organic frameworks
      Zhuang, Wenjuan; Yuan, Daqiang; Li, Jian-Rong; Luo, Zhiping; Zhou, Hong-Cai; Bashir, Sajid; Liu, Jingbo
      Advanced Healthcare Materials (2012), 1 (2), 225-238CODEN: AHMDBJ; ISSN:2192-2640. (Wiley-VCH Verlag GmbH & Co. KGaA)
      A novel Co based metal-org. framework (MOF) was tested as an antibacterial agent and is highly effective at inactivating model microorganisms such as Gram-neg. bacteria, Escherichia coli (strains DH5alpha and XL1-Blue). In Co4, the Co serves as a central element and an octa-topic carboxylate ligand, tetrakis[(3,5-dicarboxyphenyl)oxamethyl]methane (TDM8-) serves as a bridging linker. X-ray crystallog. studies indicate that Co-TDM crystallizes in tetragonal space group P‾421m with a porous 3-dimensional framework. The potency of the Co-TDM disinfectant was evaluated using a minimal bactericidal concn. (MBC) benchmark and is 10-15 ppm within a short incubation time period (<60 min). Compared with previous work using Ag nanoparticles and Ag-modified TiO2 nanocomposites over the same time period, the MBC and effectiveness of Co-TDM are superior. Electron microscopy images indicate that the Co-TDM displayed distinctive grain boundaries and well-developed reticulates. The Co active sites rapidly catalyzed the lipid peroxidn., causing rupture of the bacterial membrane followed by inactivation, with 100% recycling and high persistence (>4 wk). This MOF-based approach may lead to a new paradigm for MOF applications in diverse biol. fields due to their inherent porous structure, tunable surface functional groups, and adjustable metal coordination environments.
    14. 14
      Wang, P.-L.; Xie, L.-H.; Joseph, E. A.; Li, J.-R.; Su, X.-O.; Zhou, H.-C. Metal-Organic Frameworks for Food Safety. Chem. Rev. 2019, 119, 10638– 10690,  DOI: 10.1021/acs.chemrev.9b00257
      14
      Metal-Organic Frameworks for Food Safety
      Wang, Pei-Long; Xie, Lin-Hua; Joseph, Elizabeth A.; Li, Jian-Rong; Su, Xiao-Ou; Zhou, Hong-Cai
      Chemical Reviews (Washington, DC, United States) (2019), 119 (18), 10638-10690CODEN: CHREAY; ISSN:0009-2665. (American Chemical Society)
      A review. Food safety is a prevalent concern around the world. As such, detection, removal, and control of risks and hazardous substances present from harvest to consumption will always be necessary. Metal-org. frameworks (MOFs), a class of functional materials, possess unique phys. and chem. properties, demonstrating promise in food safety applications. In this review, the synthesis and porosity of MOFs are first introduced by some representative examples that pertain to the field of food safety. Following that, the application of MOFs and MOF-based materials in food safety monitoring, food processing, covering preservation, sanitation, and packaging is overviewed. Future perspectives, as well as potential opportunities and challenges faced by MOFs in this field will also be discussed. This review aims to promote the development and progress of MOF chem. and application research in the field of food safety, potentially leading to novel solns.
    15. 15
      Wyszogrodzka, G.; Marszałek, B.; Gil, B.; Dorożyński, P. Metal-Organic Frameworks: Mechanisms of Antibacterial Action and Potential Applications. Drug Discovery Today 2016, 21, 1009– 1018,  DOI: 10.1016/j.drudis.2016.04.009
      15
      Metal-organic frameworks: mechanisms of antibacterial action and potential applications
      Wyszogrodzka, Gabriela; Marszalek, Bartosz; Gil, Barbara; Dorozynski, Przemyslaw
      Drug Discovery Today (2016), 21 (6), 1009-1018CODEN: DDTOFS; ISSN:1359-6446. (Elsevier Ltd.)
      The growing resistance of pathogens to conventional antibiotics has become a public health problem and raises the need to seek new effective solns. Metal-org. frameworks (MOFs) are porous, hybrid materials comprising metal ions linked by org. binding ligands. The possibility of using a variety of chem. building components in MOFs enables the formation of structures with desired properties. They can act as a reservoir of metal ions, providing their gradual release and resulting in a sustained antibacterial action analogous to that proposed for metal/metal oxide nanoparticles (NPs) but different to that of antibiotics. These features make MOFs promising candidates for pharmaceutical and biomedical applications, as illustrated by examples discussed in this review.
    16. 16
      Cheung, Y. H.; Ma, K.; van Leeuwen, H. C.; Wasson, M. C.; Wang, X.; Idrees, K. B.; Gong, W.; Cao, R.; Mahle, J. J.; Islamoglu, T.; Peterson, G. W.; de Koning, M. C.; Farha, O. K.; Farha, O. K. Immobilized Regenerable Active Chlorine within a Zirconium-Based MOF Textile Composite to Eliminate Biological and Chemical Threats. J. Am. Chem. Soc. 2021, 143, 16777– 16785,  DOI: 10.1021/jacs.1c08576
      16
      Immobilized Regenerable Active Chlorine within a Zirconium-Based MOF Textile Composite to Eliminate Biological and Chemical Threats
      Cheung, Yuk Ha; Ma, Kaikai; van Leeuwen, Hans C.; Wasson, Megan C.; Wang, Xingjie; Idrees, Karam B.; Gong, Wei; Cao, Ran; Mahle, John J.; Islamoglu, Timur; Peterson, Gregory W.; de Koning, Martijn C.; Xin, John H.; Farha, Omar K.
      Journal of the American Chemical Society (2021), 143 (40), 16777-16785CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)
      The most recent global health crisis caused by the SARS-CoV-2 outbreak and the alarming use of chem. warfare agents highlight the necessity to produce efficient protective clothing and masks against biohazard and chem. threats. However, the development of a multifunctional protective textile is still behind to supply adequate protection for the public. To tackle this challenge, we designed multifunctional and regenerable N-chlorine based biocidal and detoxifying textiles using a robust zirconium metal-org. framework (MOF), UiO-66-NH2, as a chlorine carrier which can be easily coated on textile fibers. A chlorine bleaching converted the amine groups located on the MOF linker to active N-chlorine structures. The fibrous composite exhibited rapid biocidal activity against both Gram-neg. bacteria (E. coli) and Gram-pos. bacteria (S. aureus) with up to a 7 log redn. within 5 min for each strain as well as a 5 log redn. of SARS-CoV-2 within 15 min. Moreover, the active chlorine loaded MOF/fiber composite selectively and rapidly degraded sulfur mustard and its chem. simulant 2-chloroethyl Et sulfide (CEES) with half-lives less than 3 min. The versatile MOF-based fibrous composite designed here has the potential to serve as protective cloth against both biol. and chem. threats.
    17. 17
      Giliopoulos, D.; Zamboulis, A.; Giannakoudakis, D.; Bikiaris, D.; Triantafyllidis, K. Polymer/Metal Organic Framework (MOF) Nanocomposites for Biomedical Applications. Molecules 2020, 25, 185,  DOI: 10.3390/molecules25010185
      17
      Polymer/metal organic framework (MOF) nanocomposites for biomedical applications
      Giliopoulos, Dimitrios; Zamboulis, Alexandra; Giannakoudakis, Dimitrios; Bikiaris, Dimitrios; Triantafyllidis, Konstantinos
      Molecules (2020), 25 (1), 185CODEN: MOLEFW; ISSN:1420-3049. (MDPI AG)
      A review. The utilization of polymer/metal org. framework (MOF) nanocomposites in various biomedical applications has been widely studied due to their unique properties that arise from MOFs or hybrid composite systems. This review focuses on the types of polymer/MOF nanocomposites used in drug delivery and imaging applications. Initially, a comprehensive introduction to the synthesis and structure of MOFs and bio-MOFs is presented. Subsequently, the properties and the performance of polymer/MOF nanocomposites used in these applications are examd., in relation to the approach applied for their synthesis: (i) non-covalent attachment, (ii) covalent attachment, (iii) polymer coordination to metal ions, (iv) MOF encapsulation in polymers, and (v) other strategies. A crit. comparison and discussion of the effectiveness of polymer/MOF nanocomposites regarding their synthesis methods and their structural characteristics is presented.
    18. 18
      Jaros, S. W.; Guedes da Silva, M. F. C.; Florek, M.; Smoleński, P.; Pombeiro, A. J. L.; Kirillov, A. M. Silver(I) 1,3,5-Triaza-7-Phosphaadamantane Coordination Polymers Driven by Substituted Glutarate and Malonate Building Blocks: Self-Assembly Synthesis, Structural Features, and Antimicrobial Properties. Inorg. Chem. 2016, 55, 5886– 5894,  DOI: 10.1021/acs.inorgchem.6b00186
      18
      Silver(I) 1,3,5-Triaza-7-phosphaadamantane Coordination Polymers Driven by Substituted Glutarate and Malonate Building Blocks: Self-Assembly Synthesis, Structural Features, and Antimicrobial Properties
      Jaros, Sabina W.; Guedes da Silva, M. Fatima C.; Florek, Magdalena; Smolenski, Piotr; Pombeiro, Armando J. L.; Kirillov, Alexander M.
      Inorganic Chemistry (2016), 55 (12), 5886-5894CODEN: INOCAJ; ISSN:0020-1669. (American Chemical Society)
      Three new bioactive silver(I) coordination polymers formulated as [Ag2(μ2-PTA)(μ3-PTA)(μ2-pga)(H2O)]n·6H2O (1), [Ag2(μ2-PTA)(μ3-PTA)(Hpmal)2]n·2H2O (2), and [Ag(μ3-PTA) (Hdmga)]n (3) were self-assembled from Ag2O, 1,3,5-triaza-7-phosphaadamantane (PTA), and a substituted dicarboxylic acid (3-phenylglutaric acid (H2pga), phenylmalonic acid (H2pmal), or 3,3-dimethylglutaric acid (H2dmga)) as an ancillary ligand. Compds. 1-3 were fully characterized by IR and NMR spectroscopy, ESI-MS(±), elemental anal., and single-crystal x-ray diffraction, revealing that their architectural and topol. diversity is governed by structural modulation of a dicarboxylate building block. The structures vary from a 1D cyclic chain with the SP 1-periodic net (4,4)(0,2) topol. in 2 to distinct 2D metal-org. layers with the cem-d and hcb topologies in 1 and 3, resp. In addn., compds. 1-3 exhibit a notable antimicrobial efficiency against a panel of common Gram-neg. (E. coli and P. aeruginosa) and Gram-pos. (S. aureus) bacteria and yeast (C. albicans). The best normalized min. inhibitory concns. (normalized MIC) of 11-23 nmol mL-1 (for bacterial strains) or 68 nmol mL-1 (for a yeast strain) are shown by compd. 2, and the eventual structure-bioactivity correlations are discussed.
    19. 19
      Jaros, S. W.; Guedes da Silva, M. F. C.; Król, J.; Conceição Oliveira, M.; Smoleński, P.; Pombeiro, A. J. L.; Kirillov, A. M. Bioactive Silver–Organic Networks Assembled from 1,3,5-Triaza-7-Phosphaadamantane and Flexible Cyclohexanecarboxylate Blocks. Inorg. Chem. 2016, 55, 1486– 1496,  DOI: 10.1021/acs.inorgchem.5b02235
      19
      Bioactive Silver-Organic Networks Assembled from 1,3,5-Triaza-7-phosphaadamantane and Flexible Cyclohexanecarboxylate Blocks
      Jaros, Sabina W.; Guedes da Silva, M. Fatima C.; Krol, Jaroslaw; Conceicao Oliveira, M.; Smolenski, Piotr; Pombeiro, Armando J. L.; Kirillov, Alexander M.
      Inorganic Chemistry (2016), 55 (4), 1486-1496CODEN: INOCAJ; ISSN:0020-1669. (American Chemical Society)
      Three novel bioactive silver-org. networks, namely, the 2D polymer [Ag(μ3-PTA)(chc)]n·n(Hchc)·2nH2O (1), the 3D bioMOF [Ag2(μ3-PTA)2(μ2-chdc)]n·5nH2O (2), and the 2D polymer [Ag2(μ2-PTA)2(μ4-H2chtc)]n·6nH2O (3), were constructed from 1,3,5-triaza-7-phosphaadamantane (PTA) and various flexible cyclohexanecarboxylic acids as building blocks {cyclohexanecarboxylic (Hchc), 1,4-cyclohexanedicarboxylic (H2chdc), and 1,2,4,5-cyclohexanetetracarboxylic (H4chtc) acid, resp.}. The obtained products 1-3 were fully characterized by IR and NMR spectroscopy, ESI-MS(±) spectrometry, elemental and thermogravimetric (TGA) analyses, and single-crystal and powder X-ray diffraction. Their structural diversity originates from distinct coordination modes of cyclohexanecarboxylate moieties as well as from the presence of unconventional N,N,P-tridentate or N,P-bidentate PTA spacers. Topol. classification of underlying metal-org. networks was performed, disclosing the hcb, 4,4L28, and a rare fsc-3,4-Pbcn-3 topol. in 1, 2, and 3, resp. Moreover, combination of aq. soly. (S25°C ≈ 4-6 mg mL-1), air stability, and appropriate coordination environments around silver centers favors a release of bioactive Ag+ ions by 1-3, which thus act as potent antibacterial and antifungal agents against Gram-pos. (S. aureus) and Gram-neg. (E. coli and P. aeruginosa) bacteria as well as a yeast (C. albicans). The best normalized min. inhibitory concns. (normalized MIC) of 10-18 (for bacterial strains) or 57 nmol mL-1 (for a yeast strain) were achieved. Detailed ESI-MS studies were performed, confirming the relative stability of 1-3 in soln. and giving addnl. insight on the self-assembly formation of polycarboxylate Ag-PTA derivs. and their crystal growth process.
    20. 20
      Smoleński, P.; Jaros, S. W.; Pettinari, C.; Lupidi, G.; Quassinti, L.; Bramucci, M.; Vitali, L. A.; Petrelli, D.; Kochel, A.; Kirillov, A. M. New Water-Soluble Polypyridine Silver(I) Derivatives of 1,3,5-Triaza-7-Phosphaadamantane (PTA) with Significant Antimicrobial and Antiproliferative Activities. Dalton Trans. 2013, 42, 6572– 6581,  DOI: 10.1039/c3dt33026e
      20
      New water-soluble polypyridine silver(I) derivatives of 1,3,5-triaza-7-phosphaadamantane (PTA) with significant antimicrobial and antiproliferative activities
      Smolenski, Piotr; Jaros, Sabina W.; Pettinari, Claudio; Lupidi, Giulio; Quassinti, Luana; Bramucci, Massimo; Vitali, Luca A.; Petrelli, Dezemona; Kochel, Andrzej; Kirillov, Alexander M.
      Dalton Transactions (2013), 42 (18), 6572-6581CODEN: DTARAF; ISSN:1477-9226. (Royal Society of Chemistry)
      Silver(I) coordination polymers [Ag(N-N)(μ-PTA)]n(X)n (1, 2, 4-8, 10, 11) and discrete monomers [Ag(N-N)(PTA)2](X) (3, 9) {N-N = bpy (1-3), dtbpy (4), neocup (5, 6), phen (7-9), dione (10, 11); X = NO3 (1, 3, 5, 7, 9, 10), PF6 (2, 4, 6, 8, 11)} were generated by self-assembly reactions, in MeOH at ∼25°, of AgNO3 or AgPF6 with 1,3,5-triaza-7-phosphaadamantane (PTA) and the corresponding polypyridines, 2,2'-bipyridine (bpy), 4,4'-di-tert-butyl-2,2'-bipyridine (dtbpy), 1,10-phenanthroline (phen), 2,9-dimethyl-1,10-phenanthroline (neocup) and 1,10-phenanthroline-5,6-dione. The compds. were obtained as air and light stable solids and characterized by IR, 1H and 31P{1H} NMR spectroscopy, ESI+-MS and elemental analyses. The crystal structure of 1 was detd. by single crystal x-ray diffraction anal., revealing infinite 1-dimensional (1D) linear chains driven by μ-PTA N,P-linkers. Apart from representing the first examples of the metal-PTA derivs. bearing polypyridine ligands, 1-11 also feature soly. in water (S25°C ≈ 4-18 mg mL-1). Selected compds. (1, 3, 5, 7, 9 and 10) were thus tested for their biol. properties and found to exhibit significant antibacterial and antifungal activities, screened in vitro against the std. strains of Staphylococcus aureus, Staphylococcus pyogenes, Staphylococcus pneumoniae, Staphylococcus sanguinis, Staphylococcus mutans, Enterococcus faecalis, Pseudomonas aeruginosa, Escherichia coli and Candida albicans. Also, the compds. 5, 7, 9 and 10 show a pronounced antiproliferative activity against human malignant melanoma (A375), and the effects on the inhibition of tumor cells in vitro are in agreement with the DNA-binding studies.
    21. 21
      Fernandes, T. A.; Costa, I. F. M.; Jorge, P.; Sousa, A. C.; André, V.; Cerca, N.; Kirillov, A. M. Silver(I) Coordination Polymers Immobilized into Biopolymer Films for Antimicrobial Applications. ACS Appl. Mater. Interfaces 2021, 13, 12836– 12844,  DOI: 10.1021/acsami.0c19446
      21
      Silver(I) Coordination Polymers Immobilized into Biopolymer Films for Antimicrobial Applications
      Fernandes, Tiago A.; Costa, Ines F. M.; Jorge, Paula; Sousa, Ana Catarina; Andre, Vania; Cerca, Nuno; Kirillov, Alexander M.
      ACS Applied Materials & Interfaces (2021), 13 (11), 12836-12844CODEN: AAMICK; ISSN:1944-8244. (American Chemical Society)
      This study describes a template-mediated self-assembly synthesis, full characterization, and structural features of two new silver-based bioactive coordination polymers (CPs) and their immobilization into acrylated epoxidized soybean oil (ESOA) biopolymer films for antimicrobial applications. The 3D silver(I) CPs [Ag4(μ8-H2pma)2]n·4nH2O (1) and [Ag5(μ6-H0.5tma)2(H2O)4]n·2nH2O (2) were generated from AgNO3 and pyromellitic (H4pma) or trimesic (H3tma) acid, also using N,N'-dimethylethanolamine (Hdmea) as a template. Both 1 and 2 feature the intricate 3D layer-pillared structures driven by distinct polycarboxylate blocks. Topol. anal. revealed binodal nets with the flu and tcj/hc topol. in 1 and 2, resp. These CPs were used for fabricating new hybrid materials, namely, by doping the [ESOA]n biopolymer films with very low amts. of 1 and 2 (0.05, 0.1, and 0.5%). Their antimicrobial activity and ability to impair bacterial biofilm formation were investigated in detail against both Gram-pos. (Staphylococcus epidermidis and Staphylococcus aureus) and Gram-neg. (Pseudomonas aeruginosa and Escherichia coli) bacteria. Both silver(I) CPs and derived biopolymer films showed activity against all the tested bacteria in a concn.-dependent manner. Compd. 1 exhibited a more pronounced activity, esp. in preventing biofilm growth, with mean bacterial load redns. ranging from 3.7 to 4.3 log against the four bacteria (99.99% bacterial eradication). The present work thus opens up antibiofilm applications of CP-doped biopolymers, providing new perspectives and very promising results for the design of functional biomaterials.
    22. 22
      Abram, S. L.; Fromm, K. M. Handling (Nano)Silver as Antimicrobial Agent: Therapeutic Window, Dissolution Dynamics, Detection Methods and Molecular Interactions. Chem.─Eur. J. 2020, 26, 10948– 10971,  DOI: 10.1002/chem.202002143
      22
      Handling (Nano)Silver as Antimicrobial Agent: Therapeutic Window, Dissolution Dynamics, Detection Methods and Molecular Interactions
      Abram, Sarah-Luise; Fromm, Katharina M.
      Chemistry - A European Journal (2020), 26 (48), 10948-10971CODEN: CEUJED; ISSN:0947-6539. (Wiley-VCH Verlag GmbH & Co. KGaA)
      A review. Silver is an antimicrobial agent well known since antiquity. With the emergence of multiresistant bacteria, it has come back into the focus of research, and ionic as well as nano-sized silver have been studied in vitro and in vivo. The results are controversial, silver being discussed as the "silver bullet" or a "wolf in sheep's clothing". A thorough search of literature from chem., materials and environmental science, biol. and medicine led to this Review which summarizes the potential use of silver and its compds. in medicine, ongoing processes of dissoln. and the different methods by which this usefulness can be evaluated. It also highlights the therapeutic window of silver, mechanistic interactions of silver and biol. media as well as best practices for handling silver in a biomedical environment. This Review reflects the current knowhow and observations, and may thus give hints and guidelines to understand and interpret the obsd. effects.
    23. 23
      Eckhardt, S.; Brunetto, P. S.; Gagnon, J.; Priebe, M.; Giese, B.; Fromm, K. M. Nanobio Silver: Its Interactions with Peptides and Bacteria, and Its Uses in Medicine. Chem. Rev. 2013, 113, 4708– 4754,  DOI: 10.1021/cr300288v
      23
      Nanobio Silver: Its Interactions with Peptides and Bacteria, and Its Uses in Medicine
      Eckhardt, Sonja; Brunetto, Priscilla S.; Gagnon, Jacinthe; Priebe, Magdalena; Giese, Bernd; Fromm, Katharina M.
      Chemical Reviews (Washington, DC, United States) (2013), 113 (7), 4708-4754CODEN: CHREAY; ISSN:0009-2665. (American Chemical Society)
      A review of the interactions of silver with amino acids, peptides and bacteria and the various types of silver-contg. compds and nanomaterials and their biocompatibilities.
    24. 24
      Horcajada, P.; Gref, R.; Baati, T.; Allan, P. K.; Maurin, G.; Couvreur, P.; Férey, G.; Morris, R. E.; Serre, C. Metal-Organic Frameworks in Biomedicine. Chem. Rev. 2012, 112, 1232– 1268,  DOI: 10.1021/cr200256v
      24
      Metal-Organic Frameworks in Biomedicine
      Horcajada, Patricia; Gref, Ruxandra; Baati, Tarek; Allan, Phoebe K.; Maurin, Guillaume; Couvreur, Patrick; Ferey, Gerard; Morris, Russell E.; Serre, Christian
      Chemical Reviews (Washington, DC, United States) (2012), 112 (2), 1232-1268CODEN: CHREAY; ISSN:0009-2665. (American Chemical Society)
      A review. Coordination polymers or MOFs (metal-org. frameworks) as porous solids for biomedical are reviewed.
    25. 25
      Zheng, K.; Setyawati, M. I.; Leong, D. T.; Xie, J. Embedding Ultrasmall Ag Nanoclusters in Luria-Bertani Extract via Light Irradiation for Enhanced Antibacterial Activity. Coord. Chem. Rev. 2018, 357, 1– 17,  DOI: 10.1016/j.ccr.2017.11.019
      25
      Antimicrobial silver nanomaterials
      Zheng, Kaiyuan; Setyawati, Magdiel Inggrid; Leong, David Tai; Xie, Jianping
      Coordination Chemistry Reviews (2018), 357 (), 1-17CODEN: CCHRAM; ISSN:0010-8545. (Elsevier B.V.)
      Antibiotic resistance is considered as one of the greatest health threats worldwide, and we are in a staring competition with microbes as antibiotic resistance mounts faster than our current rate of developing new and effective antibiotics. Therefore, newer metal-based antimicrobial agents with easily tuned physicochem. properties have been developed to fight against these antibiotic resistant bacteria. In this review, we begin with describing the mode of action of silver nanoparticles (Ag NPs) in damaging the bacterial extracellular membrane and their intracellular components that allows them to exhibit wide spectrum antimicrobial effect. The review also contains our insights on understanding not only the correlation between the NPs' physicochem. properties and their bactericidal mode of action but also the possible strategies to tune these physicochem. properties to optimize their bactericidal properties. The second focus of this review is on the emerging and highly efficient antimicrobial agents, ultrasmall Ag nanoclusters (Ag NCs). Ag NCs are ultrasmall NPs with core sizes less than 2 nm, and they contain "countable" Ag atoms as the core, which is protected by a certain no. of org. ligands. The atomically precise property of Ag NCs provides a good platform to design and manipulate Ag NCs at at. level to achieve optimized antimicrobial efficacy, which also favor the antimicrobial mechanism study.
    26. 26
      Davoudi, Z. M.; Kandjani, A. E.; Bhatt, A. I.; Kyratzis, I. L.; O’Mullane, A. P.; Bansal, V. Hybrid Antibacterial Fabrics with Extremely High Aspect Ratio Ag/AgTCNQ Nanowires. Adv. Funct. Mater. 2014, 24, 1047– 1053,  DOI: 10.1002/adfm.201302368
      26
      Hybrid Antibacterial Fabrics with Extremely High Aspect Ratio Ag/AgTCNQ Nanowires
      Davoudi, Zahra Mohammad; Kandjani, Ahmad Esmaielzadeh; Bhatt, Anand I.; Kyratzis, Ilias L.; O'Mullane, Anthony P.; Bansal, Vipul
      Advanced Functional Materials (2014), 24 (8), 1047-1053CODEN: AFMDC6; ISSN:1616-301X. (Wiley-VCH Verlag GmbH & Co. KGaA)
      This study reports the synthesis of extremely high aspect ratios (>3000) org. semiconductor nanowires of Ag-tetracyanoquinodimethane (AgTCNQ) on the surface of a flexible Ag fabric for the first time. These one-dimensional (1D) hybrid Ag/AgTCNQ nanostructures are attained by a facile, soln.-based spontaneous reaction involving immersion of Ag fabrics in an acetonitrile soln. of TCNQ. Further, it is discovered that these AgTCNQ nanowires show outstanding antibacterial performance against both Gram neg. and Gram pos. bacteria, which outperforms that of pristine Ag. The outcomes of this study also reflect upon a fundamentally important aspect that the antimicrobial performance of Ag-based nanomaterials may not necessarily be solely due to the amt. of Ag+ ions leached from these nanomaterials, but that the nanomaterial itself may also play a direct role in the antimicrobial action. Notably, the applications of metal-org. semiconducting charge transfer complexes of metal-7,7,8,8-tetracyanoquinodimethane (TCNQ) have been predominantly restricted to electronic applications, except from our recent reports on their (photo)catalytic potential and the current case on antimicrobial prospects. This report on growth of these metal-TCNQ complexes on a fabric not only widens the window of these interesting materials for new biol. applications, it also opens the possibilities for developing large-area flexible electronic devices by growing a range of metal-org. semiconducting materials directly on a fabric surface.
    27. 27
      Chen, J.; Wang, F.; Liu, Q.; Du, J. Antibacterial Polymeric Nanostructures for Biomedical Applications. Chem. Commun. 2014, 50, 14482– 14493,  DOI: 10.1039/c4cc03001j
      27
      Antibacterial polymeric nanostructures for biomedical applications
      Chen, Jing; Wang, Fangyingkai; Liu, Qiuming; Du, Jianzhong
      Chemical Communications (Cambridge, United Kingdom) (2014), 50 (93), 14482-14493CODEN: CHCOFS; ISSN:1359-7345. (Royal Society of Chemistry)
      A review. The high incidence of bacterial infection and the growing resistance of bacteria to conventional antibiotics have resulted in the strong need for the development of new generation of antibiotics. Nano-sized particles have been considered as novel antibacterial agents with high surface area and high reactivity. The overall antibacterial properties of antimicrobial nanostructures can be significantly enhanced compared with conventional antibacterial agents not in a regular nanostructure, showing a better effect in inhibiting the growth and reprodn. of microbials such as bacteria and fungi, etc. In this review, recent advances in the research and applications of antimicrobial polymeric nanostructures have been highlighted, including silver-decorated polymer micelles and vesicles, antimicrobial polymer micelles and vesicles, and antimicrobial peptide-based vesicles, etc. Furthermore, we proposed the current challenges and future research directions in the field of antibacterial polymeric nanostructures for the real-world biomedical applications.
    28. 28
      Arenas-Vivo, A.; Amariei, G.; Aguado, S.; Rosal, R.; Horcajada, P. An Ag-loaded Photoactive Nano-metal Organic Framework as a Promising Biofilm Treatment. Acta Biomater. 2019, 97, 490– 500,  DOI: 10.1016/j.actbio.2019.08.011
      28
      An Ag-loaded photoactive nano-metal organic framework as a promising biofilm treatment
      Arenas-Vivo, Ana; Amariei, Georgiana; Aguado, Sonia; Rosal, Roberto; Horcajada, Patricia
      Acta Biomaterialia (2019), 97 (), 490-500CODEN: ABCICB; ISSN:1742-7061. (Elsevier Ltd.)
      Surface biofilm inhibition is still currently a considerable challenge. Among other organisms, Staphylococcus aureus is notable for its ability to form a strong biofilm with proved resistance to chemotherapy. Contamination of high-touch surfaces with S. aureus biofilm not only promotes disease spread but also generates tremendous health-assocd. costs. Therefore, development of new bactericidal and antiadhesive surface coatings is a priority. Considering that metal-org. frameworks (MOFs) have recently emerged as promising antibacterial agents, we originally report here the synthesis of a multi-active silver-contg. nanoscaled MOF composite as a potential surface coating against S. aureus biofilm owing to a triple effect: intrinsic bactericide activity of the MOF, biocidal character of silver nanoparticles (AgNPs), and photoactivity after UVA irradn. AgNPs were successfully entrapped within the benchmarked nanoscaled porous photoactive titanium(IV) aminoterephthalate MIL-125(Ti)NH2 using a simple and efficient impregnation-redn. method. After complete characterization of the composite thin film, its antibacterial and anti-adherent properties were fully evaluated. After UVA irradn., the composite coating exhibited relevant bacterial inhibition and detachment, improved ligand-to-cluster charge transfer, and steady controlled delivery of Ag+. These promising results establish the potential of this composite as an active coating for biofilm treatment on high-touch surfaces (e.g., surgical devices, door knobs, and rail bars). Surface contamination due to bacterial biofilm formation is still a demanding issue, as it causes severe disease spread. One possible soln. is the development of antifouling and antibacterial surface coatings. In this work, we originally propose the use of photoactive metal-org. frameworks (MOFs) for biofilm treatment. The novelty of this work relies on the following: i. the treatment of strongly contaminated surfaces, as previous studies with MOFs have exclusively addressed biofilm prevention; ii. this pioneering work reports both antiadherent effect, which removes the biofilm, and bacterial inhibition; iii. our original successful strategy has never been proposed thus far, involving the multi-active combination of 1. intrinsic antibacterial effect of a photoactive titanium-based nanoMOF, 2. immobilization of biocide silver nanoparticles, and 3. improved anti-bioadherent effect upon irradn. of the composite coating.
    29. 29
      Nishanthi, S. T.; Yadav, K. K.; Baruah, A.; Vaghasiya, K.; Verma, R. K.; Ganguli, A. K.; Jha, M. Nanostructured Silver Decorated Hollow Silica and their Application in the Treatment of Microbial Contaminated Water at Room Temperature. New J. Chem. 2019, 43, 8993– 9001,  DOI: 10.1039/c9nj01049a
      29
      Nanostructured silver decorated hollow silica and their application in the treatment of microbial contaminated water at room temperature
      Nishanthi, S. T.; Yadav, Krishna Kumar; Baruah, Arabinda; Vaghasiya, Kalpesh; Verma, Rahul Kumar; Ganguli, Ashok K.; Jha, Menaka
      New Journal of Chemistry (2019), 43 (23), 8993-9001CODEN: NJCHE5; ISSN:1144-0546. (Royal Society of Chemistry)
      The present study describes the synthesis of mesoporous silicon dioxide (silica) spheres decorated with silver nanoparticles and the investigation of their antimicrobial properties. The sol-gel method was used for the synthesis of mesoporous hollow silica spheres using tetra-Et orthosilicate (TEOS) as the silica source. Uniform hollow spheres (∼300 nm) with a thin shell of silica (∼40 nm) and a high surface area (516 m2 g-1) were obtained after calcination at 550 °C. Furthermore, silver nanoparticles were decorated on the surface of the hollow structure of silica by the adsorption of silver ions at various concns. followed by redn. using sodium borohydride. Microscopic studies showed that metallic silver was uniformly distributed over the surface of the hollow silica. The as-obtained silver decorated hollow silica exhibited an excellent antibacterial activity against Escherichia coli (E. coli) compared to that of bare hollow silica, which makes them suitable candidates for the economical treatment of bacteria-contaminated water.
    30. 30
      Zhang, Y.; Sun, P.; Zhang, L.; Wang, Z.; Wang, F.; Dong, K.; Liu, Z.; Ren, J.; Qu, X. Silver-Infused Porphyrinic Metal–Organic Framework: Surface-Adaptive, On-Demand Nanoplatform for Synergistic Bacteria Killing and Wound Disinfection. Adv. Funct. Mater. 2019, 29, 1808594,  DOI: 10.1002/adfm.201808594
      There is no corresponding record for this reference.
    31. 31
      Marchetti, F.; Palmucci, J.; Pettinari, C.; Pettinari, R.; Marangoni, M.; Ferraro, S.; Giovannetti, R.; Scuri, S.; Grappasonni, I.; Cocchioni, M.; Maldonado Hodar, F. J.; Gunnella, R. Preparation of Polyethylene Composites Containing Silver(I) Acylpyrazolonato Additives and SAR Investigation of Their Antibacterial Activity. ACS Appl. Mater. Interfaces 2016, 8, 29676– 29687,  DOI: 10.1021/acsami.6b09742
      31
      Preparation of Polyethylene Composites Containing Silver(I) Acylpyrazolonato Additives and SAR Investigation of their Antibacterial Activity
      Marchetti, Fabio; Palmucci, Jessica; Pettinari, Claudio; Pettinari, Riccardo; Marangoni, Mirko; Ferraro, Stefano; Giovannetti, Rita; Scuri, Stefania; Grappasonni, Iolanda; Cocchioni, Mario; Maldonado Hodar, Francisco Jose; Gunnella, Roberto
      ACS Applied Materials & Interfaces (2016), 8 (43), 29676-29687CODEN: AAMICK; ISSN:1944-8244. (American Chemical Society)
      Novel composite materials PEn (n = 1-9) have been prepd. by an easily up-scalable embedding procedure of three different families of Ag(I) acylpyrazolonato complexes in polyethylene (PE) matrix. In details, PE1-PE3 composites contain polynuclear [Ag(QR)]n complexes, PE4-PE6 contain mononuclear [Ag(QR)(L)m] complexes and PE7-PE9 are loaded with mononuclear [Ag(QR) (PPh3)2] complexes, resp. (where L = 1-methylimidazole or 2-ethylimidazole, m = 1 or 2, and HQR = 1-phenyl-3-methyl-4-RC(=O)-5-pyrazolone, where in detail HQfb, R = -CF2CF2CF3; HQcy, R = -cyclo-C6H11; HQbe, R = -C(H)=C(CH3)2). The PEn composites, prepd. by using a 1:1000 wt./wt. silver additive/polyethylene ratio, have been characterized in bulk by IR spectroscopy and TGA analyses, which confirmed that the properties of polyethylene matrix are essentially unchanged. AFM, SEM, and EDX surface techniques show that silver additives form agglomerates with dimensions 10-100 μm on the polyethylene surface, with a slight increment of surface roughness of pristine plastic within 50 nm. However, the elastic properties of the composites are essentially the same of PE. The antibacterial activity of all composites has been tested against three bacterial strains (E. coli, P. aeruginosa and S. aureus) and results show that two classes of composites, PE1-PE3 and PE4-PE6, display high and persistent bactericidal and bacteriostatic activity, comparable to PE embedded with AgNO3. By contrast, composites PE7-PE9 exhibit a reduced antibacterial action. Contact and release tests in several conditions for specific migration of Ag+ from plastics, indicate a very limited but time persistent release of silver ions from PE1-PE6 composites, thus suggesting that they are potential antibacterial materials for future applications. Instead, PE7-PE9 almost do not release silver, only trace levels of silver ions being detected, in accordance with their reduced antibacterial action. None of the composites is toxic against higher organisms, as confirmed by D. magna test of ecotoxicity.
    32. 32
      Bhargava, A.; Pareek, V.; Roy Choudhury, S.; Panwar, J.; Karmakar, S. Superior Bactericidal Efficacy of Fucose-Functionalized Silver Nanoparticles against Pseudomonas aeruginosa PAO1 and Prevention of Its Colonization on Urinary Catheters. ACS Appl. Mater. Interfaces 2018, 10, 29325– 29337,  DOI: 10.1021/acsami.8b09475
      32
      Superior Bactericidal Efficacy of Fucose-Functionalized Silver Nanoparticles against Pseudomonas aeruginosa PAO1 and Prevention of Its Colonization on Urinary Catheters
      Bhargava, Arpit; Pareek, Vikram; Roy Choudhury, Subhasree; Panwar, Jitendra; Karmakar, Surajit
      ACS Applied Materials & Interfaces (2018), 10 (35), 29325-29337CODEN: AAMICK; ISSN:1944-8244. (American Chemical Society)
      Pseudomonas aeruginosa, a Gram-neg. rod-shaped bacterium is a notorious pathogen causing chronic infections. Its ability to form antibiotic-resistant biofilm has raised the need for the development of alternative treatment approaches. An ideal alternate can be silver nanoparticles known for their strong yet tunable bactericidal activity. However, their use in com. in vivo medicine could not see the light of the day because of the unwanted toxicity of silver in the host cells at higher concns. Thus, strategies which can modulate the bacterial cell-silver nanoparticle interactions thereby reducing the amt. of nanoparticles required to kill a typical no. of bacterial cells are utmost welcomed. The current work showcases one such strategy by functionalizing the silver nanoparticles with L-fucose to increase their interactions with the LecB lectins present on P. aeruginosa PAO1. The advantage of this approach lies in the higher bactericidal and antibiofilm activity of fucose-functionalized silver nanoparticles (FNPs) as compared to the citrate-capped silver nanoparticles (CNPs) of similar size and concns. The superior bactericidal potential of FNPs as demonstrated by fluorescence-assisted cell sorting, confocal laser scanning microscopy, and transmission electron microscopy analyses may be attributed to the higher reactive oxygen species generation and oxidative membrane damage. Addnl., FNPs prevented the formation of biofilms by downregulating the expression of various virulence genes at lower concns. as compared to CNPs. The practical applicability of the approach was demonstrated by preventing bacterial colonization on artificial silicone rubber surfaces. These results can be extrapolated in the treatment of catheter-assocd. urinary tract infections caused by P. aeruginosa. In conclusion, the present work strongly advocates the use of antivirulence targets and their corresponding binding residues for the augmentation of the bactericidal effect of silver nanoparticles.
    33. 33
      Rai, M. K.; Deshmukh, S. D.; Ingle, A. P.; Gade, A. K. Silver Nanoparticles: the Powerful Nanoweapon Against Multidrug-Resistant Bacteria. J. Appl. Microbiol. 2012, 112, 841– 852,  DOI: 10.1111/j.1365-2672.2012.05253.x
      33
      Silver nanoparticles: the powerful nanoweapon against multidrug-resistant bacteria
      Rai, M. K.; Deshmukh, S. D.; Ingle, A. P.; Gade, A. K.
      Journal of Applied Microbiology (2012), 112 (5), 841-852CODEN: JAMIFK; ISSN:1364-5072. (Wiley-Blackwell)
      In the present scenario, pharmaceutical and biomedical sectors are facing the challenges of continuous increase in the multidrug-resistant (MDR) human pathogenic microbes. Re-emergence of MDR microbes is facilitated by drug and/or antibiotic resistance, which is acquired way of microbes for their survival and multiplication in uncomfortable environments. MDR bacterial infections lead to significant increase in mortality, morbidity and cost of prolonged treatments. Therefore, development, modification or searching the antimicrobial compds. having bactericidal potential against MDR bacteria is a priority area of research. Silver in the form of various compds. and bhasmas have been used in Ayurveda to treat several bacterial infections since time immemorial. As several pathogenic bacteria are developing antibiotic resistance, silver nanoparticles are the new hope to treat them. This review discusses the bactericidal potential of silver nanoparticles against the MDR bacteria. This multiactional nanoweapon can be used for the treatment and prevention of drug-resistant microbes.
    34. 34
      Xie, X.; Sun, T.; Xue, J.; Miao, Z.; Yan, X.; Fang, W.; Li, Q.; Tang, R.; Lu, Y.; Tang, L.; Zha, Z.; He, T. Ag Nanoparticles Cluster with pH-Triggered Reassembly in Targeting Antimicrobial Applications. Adv. Funct. Mater. 2020, 30, 2000511,  DOI: 10.1002/adfm.202000511
      34
      Ag nanoparticles cluster with pH-triggered reassembly in targeting antimicrobial applications
      Xie, Xianli; Sun, Tian Ci; Xue, Jingzhe; Miao, Zhaohua; Yan, Xu; Fang, Wei Wei; Li, Qing; Tang, Rupei; Lu, Yang; Tang, Longxiang; Zha, Zhengbao; He, Tao
      Advanced Functional Materials (2020), 30 (17), 2000511CODEN: AFMDC6; ISSN:1616-301X. (Wiley-VCH Verlag GmbH & Co. KGaA)
      Antibacterial efficiency can be effectively improved by applying targeting antibacterial materials and strategies. Herein, the successful synthesis of uniform pH-responsive Ag nanoparticle clusters (AgNCs) is demonstrated, which can collapse and reassemble into nonuniform Ag NPs upon exposure to the acidic microenvironment of bacterial infections. This pH triggered reassembly contributes greatly to the improved antibacterial activities of AgNCs against both methicillin-resistant Staphylococcus aureus (MRSA) and Escherichia coli (E. coli). The min. inhibitory concn. and min. bactericidal concn. against MRSA are as low as 4 and 32 μg mL-1 (which are 8 and 32 μg mL-1 for E. coli), resp. In vivo skin wound healing expts. confirm AgNCs can serve as an effective wound dressing to accelerate the healing of MRSA infection. The development of responsive AgNCs offers new materials and strategies in targeting antibacterial applications.
    35. 35
      Tran, H. A.; Tran, P. A. In Situ Coatings of Silver Nanoparticles for Biofilm Treatment in Implant-Retention Surgeries: Antimicrobial Activities in Monoculture and Coculture. ACS Appl. Mater. Interfaces 2021, 13, 41435– 41444,  DOI: 10.1021/acsami.1c08239
      35
      In Situ Coatings of Silver Nanoparticles for Biofilm Treatment in Implant-Retention Surgeries: Antimicrobial Activities in Monoculture and Coculture
      Tran, Hien A.; Tran, Phong A.
      ACS Applied Materials & Interfaces (2021), 13 (35), 41435-41444CODEN: AAMICK; ISSN:1944-8244. (American Chemical Society)
      Bacterial biofilms are indicated in most medical device-assocd. infections. Treating these biofilms is challenging yet critically important for applications such as in device-retention surgeries, which can have reinfection rates of up to 80%. This in vitro study centered around our new method of treating biofilm and preventing reinfection. Ionic silver (Ag, in the form of silver nitrate) combined with dopamine and a biofilm-lysing enzyme (α-amylase) were applied to model 4-day-old Staphylococcus aureus biofilms on titanium substrates to degrade the extracellular matrix of the biofilm and kill the biofilm bacteria. In this process, the oxidative self-polymn. of dopamine converted Ag ions into Ag nanoparticles that, together with the resultant self-adhering polydopamine (PDA), formed coatings that strongly bound to the treated substrates. Surprisingly, although these Ag/PDA coatings significantly reduced S. aureus growth in std. bacterial monoculture, they showed much lower antimicrobial activity in coculture of the bacteria and osteoblastic MC3T3-E1 cells in which the bacteria were also found attached to the osteoblasts. This S. aureus- osteoblast interaction was also linked to bacterial survival against gentamicin treatment obsd. in coculture. Our study thus provided clear evidence suggesting that bacteria's interactions with tissue cells surrounding implants may significantly contribute to their resistance to antimicrobial treatment.
    36. 36
      Morones, J. R.; Elechiguerra, J. L.; Camacho, A.; Holt, K.; Kouri, J. B.; Ramírez, J. T.; Yacaman, M. J. The Bactericidal Effect of Silver Nanoparticles. Nanotechnology 2005, 16, 2346– 2353,  DOI: 10.1088/0957-4484/16/10/059
      36
      The bactericidal effect of silver nanoparticles
      Morones, Jose Ruben; Elechiguerra, Jose Luis; Camacho, Alejandra; Holt, Katherine; Kouri, Juan B.; Ramirez, Jose Tapia; Yacaman, Miguel Jose
      Nanotechnology (2005), 16 (10), 2346-2353CODEN: NNOTER; ISSN:0957-4484. (Institute of Physics Publishing)
      Nanotechnol. is expected to open new avenues to fight and prevent disease using at. scale tailoring of materials. Among the most promising nanomaterials with antibacterial properties are metallic nanoparticles, which exhibit increased chem. activity due to their large surface to vol. ratios and crystallog. surface structure. The study of bactericidal nanomaterials is particularly timely considering the recent increase of new resistant strains of bacteria to the most potent antibiotics. This has promoted research in the well known activity of silver ions and silver-based compds., including silver nanoparticles. The present work studies the effect of silver nanoparticles in the range of 1-100 nm on Gram-neg. bacteria using high angle annular dark field (HAADF) scanning TEM (STEM). Our results indicate that the bactericidal properties of the nanoparticles are size dependent, since the only nanoparticles that present a direct interaction with the bacteria preferentially have a diam. of ∼1-10 nm.
    37. 37
      Matsumura, Y.; Yoshikata, K.; Kunisaki, S.-i.; Tsuchido, T. Mode of Bactericidal Action of Silver Zeolite and its Comparison with that of Silver Nitrate. Appl. Environ. Microbiol. 2003, 69, 4278– 4281,  DOI: 10.1128/aem.69.7.4278-4281.2003
      37
      Mode of bactericidal action of silver zeolite and its comparison with that of silver nitrate
      Matsumura, Yoshinobu; Yoshikata, Kuniaki; Kunisaki, Shin-ichi; Tsuchido, Tetsuaki
      Applied and Environmental Microbiology (2003), 69 (7), 4278-4281CODEN: AEMIDF; ISSN:0099-2240. (American Society for Microbiology)
      The properties of the bactericidal action of silver zeolite as affected by inorg. salts and ion chelators were similar to those of silver nitrate. The results suggest that the contact of the bacterial cell with silver zeolite, the consequent transfer of silver ion to the cell, and the generation of reactive oxygen species in the cell are involved in the bactericidal activity of silver zeolite.
    38. 38
      Gupta, A.; Maynes, M.; Silver, S. Effects of Halides on Plasmid-mediated Silver Resistance in Escherichia Coli. Appl. Environ. Microbiol. 1998, 64, 5042– 5045,  DOI: 10.1128/aem.64.12.5042-5045.1998
      38
      Effects of halides on plasmid-mediated silver resistance in Escherichia coli
      Gupta, Amit; Maynes, Maria; Silver, Simon
      Applied and Environmental Microbiology (1998), 64 (12), 5042-5045CODEN: AEMIDF; ISSN:0099-2240. (American Society for Microbiology)
      Silver resistance of sensitive Escherichia coli J53 and resistance plasmid-contg. J53(pMG101) was affected by halides in the growth medium. The effects of halides on Ag+ resistance were measured with AgNO3 and silver sulfadiazine, both on agar and in liq. Low concns. of chloride made the differences in MICs between sensitive and resistant strains larger. High concns. of halides increased the sensitivities of both strains to Ag+.
    39. 39
      Feng, Q. L.; Wu, J.; Chen, G. Q.; Cui, F. Z.; Kim, T. N.; Kim, J. O. A mechanistic Study of the Antibacterial Effect of Silver Ions on Escherichia coli and Staphylococcus aureus. J. Biomed. Mater. Res. 2000, 52, 662– 668,  DOI: 10.1002/1097-4636(20001215)52:4<662::aid-jbm10>3.0.co;2-3
      39
      A mechanistic study of the antibacterial effect of silver ions on Escherichia coli and Staphylococcus aureus
      Feng, Q. L.; Wu, J.; Chen, G. Q.; Kim, T. N.; Kim, J. O.
      Journal of Biomedical Materials Research (2000), 52 (4), 662-668CODEN: JBMRBG; ISSN:0021-9304. (John Wiley & Sons, Inc.)
      To investigate the mechanism of inhibition of silver ions on microorganisms, two strains of bacteria, namely Gram-neg. Escherichia coli (E. coli) and Gram-pos. Staphylococcus aureus (S. aureus), were treated with AgNO3 and studied using combined electron microscopy and X-ray microanal. Similar morphol. changes occurred in both E. coli and S. aureus cells after Ag+ treatment. The cytoplasm membrane detached from the cell wall. A remarkable electron-light region appeared in the center of the cells, which contained condensed DNA mols. There are many small electron-dense granules either surrounding the cell wall or depositing inside the cells. The existence of elements of silver and sulfur in the electron-dense granules and cytoplasm detected by X-ray microanal. suggested the antibacterial mechanism of silver: DNA lost its replication ability and the protein became inactivated after Ag+ treatment. The slighter morphol. changes of S. aureus compared with E. coli recommended a defense system of S. aureus against the inhibitory effects of Ag+ ions.
    40. 40
      Krochta, J. M.; De Mulder-Johnston, C. Edible and Biodegradable Polymer Films: Challenges and Opportunities. Food Technol. 1997, 51, 61– 74
      There is no corresponding record for this reference.
    41. 41
      Cruz-Romero, M.; Kerry, J. Crop-Based Biodegradable Packaging and its Environmental Implications. CAB Rev. Perspect. Agric. Vet. Sci. Nutr. Nat. Resour. 2008, 3, 1– 25,  DOI: 10.1079/pavsnnr20083074
      There is no corresponding record for this reference.
    42. 42
      Prakash Maran, J.; Sivakumar, V.; Sridhar, R.; Prince Immanuel, V. Development of Model for Mechanical Properties of Tapioca Starch Based Edible Films. Ind. Crops Prod. 2013, 42, 159– 168,  DOI: 10.1016/j.indcrop.2012.05.011
      42
      Development of model for mechanical properties of tapioca starch based edible films
      Prakash Maran, J.; Sivakumar, V.; Sridhar, R.; Prince Immanuel, V.
      Industrial Crops and Products (2013), 42 (), 159-168CODEN: ICRDEW; ISSN:0926-6690. (Elsevier B.V.)
      Eco-efficient products are the new generation of bio-based products prepd. with sustainable materials, which agree with ecol. and economic requirements including environmentally acceptable disposal of post-user waste. Increasing environmental concerns assocd. with handling of plastic waste has emphasized the importance of developing biodegradable edible films from starch. The objective of this study is to develop models and study the individual and interactive effects of the process variables on the mech. properties of tapioca starch-based edible films using Box-Behnken design. Box-Behnken design with four factors at three levels was employed to evaluate the individual and interactive effects of process parameters (tapioca starch 1-3 g; glycerol 0.5-1.0 mL; agar 0.5-1.0 g; and span 80: 0.1-0.5 mL) on the tensile strength, elongation, Young's modulus, puncture force, and puncture deformation resp. The results were analyzed using Pareto anal. of variance (ANOVA). For each response, second order polynomial regression models were developed and it showed good fit of the exptl. data with high coeff. of detn. (R 2) and a close agreement between exptl. and predicted values was found. The response surface and contour plots were constructed for representing the relationship between the process parameters and the responses.
    43. 43
      Siddiqui, J.; Taheri, M.; Alam, A. U.; Deen, M. J. Nanomaterials in Smart Packaging Applications: A Review. Small 2021, 18, 2101171,  DOI: 10.1002/smll.202101171
      There is no corresponding record for this reference.
    44. 44
      Zhang, Y.; Ma, Q.; Critzer, F.; Davidson, P. M.; Zhong, Q. Physical and Antibacterial Properties of Alginate Films Containing Cinnamon Bark Oil and Soybean Oil. LWT--Food Sci. Technol. 2015, 64, 423– 430,  DOI: 10.1016/j.lwt.2015.05.008
      44
      Physical and antibacterial properties of alginate films containing cinnamon bark oil and soybean oil
      Zhang, Yue; Ma, Qiumin; Critzer, Faith; Davidson, P. Michael; Zhong, Qixin
      LWT--Food Science and Technology (2015), 64 (1), 423-430CODEN: LSTWB3; ISSN:0023-6438. (Elsevier Ltd.)
      Edible antimicrobial films with essential oils are potential intervention strategies to improve microbiol. safety of foods. The aim of this work was to study the effects of incorporating soybean oil (SBO) on the phys. and antibacterial properties of alginate films prepd. with 1% or 2% cinnamon bark oil (CBO). The incorporation of SBO improved the microstructure homogeneity and transparency, reduced tensile strength, elongation at break, water soly., and total solids content but had no obvious effects on the water vapor permeability of films. Films prepd. with 1% CBO had a low residual CBO after film formation and storage. For 2% CBO treatments, the addn. of SBO reduced the loss of CBO during storage of films and improved the antimicrobial activity against Escherichia coli O157:H7, Listeria monocytogenes and Salmonella enterica. The results suggest that SBO can be used to improve certain phys. characteristics and the antibacterial efficacy of edible films contg. essential oils.
    45. 45
      Xia, C.; Wang, L.; Dong, Y.; Zhang, S.; Shi, S. Q.; Cai, L.; Li, J. Soy Protein Isolate-Based Films Cross-Linked by Epoxidized Soybean Oil. RSC Adv. 2015, 5, 82765– 82771,  DOI: 10.1039/c5ra15590h
      45
      Soy protein isolate-based films cross-linked by epoxidized soybean oil
      Xia, Changlei; Wang, La; Dong, Youming; Zhang, Shifeng; Shi, Sheldon Q.; Cai, Liping; Li, Jianzhang
      RSC Advances (2015), 5 (101), 82765-82771CODEN: RSCACL; ISSN:2046-2069. (Royal Society of Chemistry)
      Epoxidized soybean oil (ESO) is an environmentally friendly crosslinking agent derived from soybean, having multiple epoxy groups in its mols. It can effectively improve tensile strength and water resistance of soy protein isolate (SPI)-based films. The properties of the SPI-based films were characterized by X-ray diffraction and attenuated total reflectance Fourier transform IR spectroscopy. The best performance of the SPI-based films was achieved when the ESO addn. was 2.5%, for which tensile modulus, tensile strength and 10% offset yield strength were increased to 265.0 MPa, 9.8 MPa and 6.8 MPa, resp. Compared to untreated SPI-based films, these were increases of 695.6%, 139.8%, and 246.6%, resp. However, the elongation at break was decreased by 67.6% due to the crosslinking between SPI and ESO. The SPI-based film modified by 5% ESO had the best water-resistance property and reduced the 24 h water absorption from 209.1% to 45.9%, which was a significant decrease of 78.1%.
    46. 46
      Liang, S.; Wang, L. A Natural Antibacterial-Antioxidant Film from Soy Protein Isolate Incorporated with Cortex Phellodendron Extract. Polymers 2018, 10, 71,  DOI: 10.3390/polym10010071
      46
      A natural antibacterial-antioxidant film from soy protein isolate incorporated with cortex Phellodendron extract
      Liang, Shumin; Wang, Lijuan
      Polymers (Basel, Switzerland) (2018), 10 (1), 71/1-71/13CODEN: POLYCK; ISSN:2073-4360. (MDPI AG)
      An active film was prepd. by incorporating cortex Phellodendron ext. (CPE, an active agent) into a soybean protein isolate (SPI). Different concns. of CPE (0%, 10%, 12.5%, 15%, 17.5%, 20%, or 22.5%, wt./wt., based on SPI) were mixed into the films characterized by Fourier transform IR spectroscopy, X-ray diffraction, SEM, thermogravimetry, tensile tests, and barrier properties. The rheol. properties of the solns. were also tested. The effects of the CPE content on the antibacterial and antioxidant activities of the films were examd. The results indicated that new hydrogen bonds formed between mols. in the films, and the crystallinity of the films decreased. The incorporation of CPE had no significant influence on the thermal stability of the films. Films contg. 15% CPE had the max. tensile strength of 6.00 MPa. The barrier properties against water vapor, oxygen, and light enhanced with the incorporation of CPE. The antioxidant activity of the SPI film was also improved. The films were effective against Staphylococcus aureus (S. aureus, Gram-pos. bacteria). These results suggest that the SPI/CPE film can potentially extend the shelf lives of foods.
    47. 47
      Pilla, S. Engineering Applications of Bioplastics and Biocomposites─An Overview. In Handbook of Bioplastics and Biocomposites Engineering Applications; Scrivener Publishing LLC., 2011; pp 1– 15.
      There is no corresponding record for this reference.
    48. 48
      Podshivalov, A.; Zakharova, M.; Glazacheva, E.; Uspenskaya, M. Gelatin/Potato Starch Edible Biocomposite Films: Correlation Between Morphology and Physical Properties. Carbohydr. Polym. 2017, 157, 1162– 1172,  DOI: 10.1016/j.carbpol.2016.10.079
      48
      Gelatin/potato starch edible biocomposite films: Correlation between morphology and physical properties
      Podshivalov, Aleksandr; Zakharova, Mariia; Glazacheva, Ekaterina; Uspenskaya, Mayya
      Carbohydrate Polymers (2017), 157 (), 1162-1172CODEN: CAPOD8; ISSN:0144-8617. (Elsevier Ltd.)
      The paper presents the results of studies of the microstructure morphol. and the operational properties of the gelatin/potato starch/glycerol edible biocomposite films varying in the starch content from 0 to 50 wt% prepd. by casting film-forming soln. and dying at 36 °C for 15 h. The biocomposite films were shown phase sepd. heterogeneous morphol. with the gelatin matrix as a continuous phase and microgranules of starch as a minor phase. It is found that when the starch content ≤ 30 wt% the phase sepn. mechanism is nucleation and grow, whereas the starch content > 30 wt% then the spinodal decompn. is the dominant mechanism. The work focuses on findings the influence of the phase sepn. mechanisms on the size of starch granules during the drying process, as well as the impact of these mechanisms on optical, frictional, mech., thermal and water-barrier properties.
    49. 49
      Mukhopadhyay, R.; Sree, K. D.; Saneeha, R.; Kale, P.; Iram, U. Preparation and Characterization of Biodegradable Plastics out of Food Wastes as Prospective and Eco-Friendly Medical Devices. Int. J. Res. Appl. Sci. Eng. Technol. 2017, 5, 134– 142
      There is no corresponding record for this reference.
    50. 50
      Gonzalez-Gutierrez, J.; Partal, P.; Garcia-Morales, M.; Gallegos, C. Development of Highly-Transparent Protein/Starch-Based Bioplastics. Bioresour. Technol. 2010, 101, 2007– 2013,  DOI: 10.1016/j.biortech.2009.10.025
      50
      Development of highly-transparent protein/starch-based bioplastics
      Gonzalez-Gutierrez, J.; Partal, P.; Garcia-Morales, M.; Gallegos, C.
      Bioresource Technology (2010), 101 (6), 2007-2013CODEN: BIRTEB; ISSN:0960-8524. (Elsevier Ltd.)
      Striving to achieve cost-competitive biomass-derived materials for the plastics industry, the incorporation of starch (corn and potato) to a base formulation of albumen and glycerol was considered. To study the effects of formulation and processing, albumen/starch-based bioplastics contg. 0-30 wt.% starch were prepd. by thermo-plastic and thermo-mech. processing. Transmittance measurements, DSC, DMTA and tensile tests were performed on the resulting bioplastics. Optical and tensile properties were strongly affected by starch concn. However, DMTA at low deformation proved to be insensitive to starch addn. Thermo-mech. processing led to transparent albumen/starch materials with values of strength at low deformation comparable to commodity plastics. Consequently, albumen biopolymers may become a biodegradable alternative to oil-derived plastics for manufg. transparent packaging and other plastic stuffs.
    51. 51
      Abdullah, A. H. D.; Pudjiraharti, S.; Karina, M.; Putri, O. D.; Fauziyyah, R. H. Fabrication and Characterization of Sweet Potato Starch-Based Bioplastics Plasticized with Glycerol. J. Biol. Sci. 2019, 19, 57– 64,  DOI: 10.3923/jbs.2019.57.64
      51
      Fabrication and characterization of sweet potato starch-based bioplastics plasticized with glycerol
      Abdullah, Akbar Hanif Dawam; Pudjiraharti, Sri; Karina, Myrtha; Putri, Oceu Dwi; Fauziyyah, Rani Hasna
      Journal of Biological Sciences (Faisalabad, Pakistan) (2019), 19 (1), 57-64CODEN: JBSFA9; ISSN:1727-3048. (Asian Network for Scientific Information)
      Background and Objective: Poor biodegradability and the contamination risk of petrochem.-based plastics encouraged the utilization of renewable resources to replace them due to their inexpensive, renewable, biodegradable and compostable properties. This study aimed to investigate the utilization of sweet potato sourced from Indonesia as a base material of bioplastic and its characteristics for food packaging application. Materials and Methods: Starch was extd. from sweet potato and bioplastics was prepd. by mixing starch with glycerol using different starch:glycerol wt./wt. ratio (2.5:1, 2.75:1, 3:1 and 3.5:1). Intermol. interactions and microstructure of bioplastics were assessed by using FTIR and SEM, resp. The phys. and mech. properties were evaluated by measuring the d., tensile strength and elongation at break. The relative hydrophobicity was examd. by measuring the water contact angle. The biodegradability was also investigated with the aid of enzymic degrdn. by microbes. Results: Microstructure of bioplastics showed the incomplete gelatinization with the increase of starch:glycerol ratio indicated by the visible inhomogeneous granules. FTIR spectra exhibited that the intermol. interaction in bioplastics occurred through C-O-H, O-H, C-H aliph. and C=O groups. Mech. properties evaluation showed that bioplastic with 3.5:1 (starch:glycerol) ratio exhibited the highest tensile strength of 2.57 MPa with the lowest elongation of 6.27%. Bioplastic with 3.5:1 (starch:glycerol) ratio also showed the highest d. and contact angle of 1.66 g cm-3 and 50.1 °, resp. The fastest enzymic degrdn. showed by the highest microbial growth was presented by bioplastic with 3.5:1 (starch:glycerol) ratio as well. Conclusion: Bioplastic with the highest sweet potato starch:glycerol ratio showed the most excellent phys., mech. and biodegradability properties.
    52. 52
      Gong, H.-Y.; Rambo, B. M.; Karnas, E.; Lynch, V. M.; Keller, K. M.; Sessler, J. L. Environmentally Responsive Threading, Dethreading, and Fixation of Anion-Induced Pseudorotaxanes. J. Am. Chem. Soc. 2011, 133, 1526– 1533,  DOI: 10.1021/ja109102k
      52
      Environmentally Responsive Threading, Dethreading, and Fixation of Anion-Induced Pseudorotaxanes
      Gong, Han-Yuan; Rambo, Brett M.; Karnas, Elizabeth; Lynch, Vincent M.; Keller, Karin M.; Sessler, Jonathan L.
      Journal of the American Chemical Society (2011), 133 (5), 1526-1533CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)
      The tetracationic macrocycle cyclo[2](2,6-di(1H-imidazol-1-yl)pyridine)[2](1,4-dimethylenebenzene) hexafluorophosphate (14+·4PF6-) acts as a large, flexible "mol. box" that supports the formation of environmentally responsive anion-induced pseudorotaxanes, as well as other extended structures, including metal-linked supramol. polyrotaxanes. Specifically, the combination of the tetracation 14+ and bis-carboxylate guests derived from 4,4'-biphenyldicarboxylic acid and 2,6-naphthalenedicarboxylic acid results in the formation of pseudorotaxanes that respond to changes in environmental stimuli, including pH and temp. The resulting structures can be "locked into place" via the addn. of a metal-linker in the form of Ag(I); this gives rise to an ordered metal-linked polyrotaxane. The interpenetrated constructs described in this article were characterized in soln. and in the solid state by one- and two-dimensional (1H and NOESY) NMR spectroscopy, as well as by mass spectrometry (ESI-MS) and single-crystal X-ray diffraction methods.
    53. 53
      Wang, H.; Wan, C.-Q.; Yang, J.; Mak, T. C. W. Ligation Behavior of an Oligo-α-sulfanylpyrazinyl Ligand in Silver(I) Complexes Containing Carboxylates. Cryst. Growth Des. 2014, 14, 3530– 3540,  DOI: 10.1021/cg500474j
      53
      Ligation Behavior of an Oligo-α-sulfanylpyrazinyl Ligand in Silver(I) Complexes Containing Carboxylates
      Wang, Han; Wan, Chong-Qing; Yang, Jin; Mak, Thomas C. W.
      Crystal Growth & Design (2014), 14 (7), 3530-3540CODEN: CGDEFU; ISSN:1528-7483. (American Chemical Society)
      Seven new Ag(I) complexes based on conformationally flexible 2,6-bis(pyrazin-2-ylthio)pyrazine (L) and selected carboxylate ligands, Ag2(L)2(L1)2 (1), [Ag(L)(L2)]∞ (2), [Ag2(L)(L3)2]∞ (3), [Ag2(L)(L4)2]∞ (4), {[Ag2(L)(L5)]· 4H2O}∞ (5), {[Ag2(L)(L6)]· 3H2O}∞ (6), and {[Ag2(L)2(L7)]· 3H2O}∞ (7) (L1 = trifluoroacetate, L2 = heptafluorobutanoate, L3 = 4-cyanobenzoate, L4 = 2-(perfluorophenoxy)acetate, L5 = 1,1'-biphenyl-4,4'-dicarboxylate, L6 = 2,2'-(1,4-phenylene)diacetate, and L7 = naphthalene-2,6-dicarboxylate), have been synthesized and structurally characterized by single-crystal x-ray diffraction analyses. In 1-7, an argentophilic Ag2 dimer is a dominant subunit, which is stabilized by a pair of bridging carboxylate groups. Complexes 1-4 are assembled with monocarboxylates, L, and Ag(I) ions. Complex 1 exists as a discrete dimeric mol., being stabilized by trans pairs of L and L1. Co-crystn. of discrete mols. and infinite chains occur in complex 2. In 3 and 4, Ag2 dimers are linked by ligands L to furnish a double-bridged chain and a ladder-like structure, resp. Complexes 5-7 are assembled with dicarboxylate spacers and flexible L, which link Ag2 units to form a 2D slablike architecture in 5, and 3D coordination frameworks in 6 and 7. In addn., the effect of the carboxylate ligands on the ligation behavior of L and supramol. assembly of the series of compds. are discussed.
    54. 54
      Fangfang, Z.; Xinpeng, B.; Wei, G.; Wang, G.; Shi, Z.; Jun, C. Effects of Virgin Coconut Oil on the Physicochemical, Morphological and Antibacterial Properties of Potato Starch-Based Biodegradable Films. Int. J. Food Sci. 2020, 55, 192– 200,  DOI: 10.1111/ijfs.14262
      54
      Effects of virgin coconut oil on the physicochemical, morphological and antibacterial properties of potato starch-based biodegradable films
      Fangfang, Zhang; Xinpeng, Bai; Wei, Gao; Wang, Guoding; Shi, Zhenzhen; Jun, Cao
      International Journal of Food Science and Technology (2020), 55 (1), 192-200CODEN: IJFTEZ; ISSN:0950-5423. (Wiley-Blackwell)
      Summary : This study investigated the effects of adding different concns. of virgin coconut oil (VCO) on the optical, mech., thermodn. and antimicrobial properties, as well as water vapor permeability and morphol. of potato starch-based biodegradable films. Increasing VCO concns. caused a rise in the light transmittance of the films from 2.13 to 4.79 mm-1 and a decrease in water vapor transmittance from 6.77 to 2.12 (10-5 GPa-1 h-1 m-1). At a VCO concn. of 14 wt% (based on potato starch), the tensile strength reached its highest value (19.98 MPa). SEM showed that the surface of the film became smoother as VCO concn. increased. The addn. of VCO inhibited the growth of Listeria monocytogenes, Staphylococcus aureus and Escherichia coli. In conclusion, VCO supplementation improved the mech., antibacterial and water barrier properties of starch-based films. These results could expand the scope of the application of starch-based films in food packaging.
    55. 55
      Altayan, M. M.; Al Darouich, T.; Karabet, F. On the Plasticization Process of Potato Starch: Preparation and Characterization. Food Biophys. 2017, 12, 397– 403,  DOI: 10.1007/s11483-017-9495-2
      There is no corresponding record for this reference.
    56. 56
      Gordon, O.; Vig Slenters, T.; Brunetto, P. S.; Villaruz, A. E.; Sturdevant, D. E.; Otto, M.; Landmann, R.; Fromm, K. M. Silver Coordination Polymers for Prevention of Implant Infection: Thiol Interaction, Impact on Respiratory Chain Enzymes, and Hydroxyl Radical Induction. Antimicrob. Agents Chemother. 2010, 54, 4208– 4218,  DOI: 10.1128/aac.01830-09
      56
      Silver coordination polymers for prevention of implant infection: thiol interaction, impact on respiratory chain enzymes, and hydroxyl radical induction
      Gordon, Oliver; Slenters, Tunde Vig; Brunetto, Priscilla S.; Villaruz, Amer E.; Sturdevant, Daniel E.; Otto, Michael; Landmann, Regine; Fromm, Katharina M.
      Antimicrobial Agents and Chemotherapy (2010), 54 (10), 4208-4218CODEN: AMACCQ; ISSN:0066-4804. (American Society for Microbiology)
      Prosthetic joint replacements are used increasingly to alleviate pain and improve mobility of the progressively older and more obese population. Implant infection occurs in about 5% of patients and entails significant morbidity and high social costs. It is most often caused by staphylococci, which are introduced perioperatively. They are a source of prolonged seeding and difficult to treat due to antibiotic resistance; therefore, infection prevention by prosthesis coating with nonantibiotic-type anti-infective substances is indicated. A renewed interest in topically used silver has fostered development of silver nanoparticles, which, however, present a potential health hazard. Here we present new silver coordination polymer networks with tailored phys. and chem. properties as nanostructured coatings on metallic implant substrates. These compds. exhibited strong biofilm sugar-independent bactericidal activity on in vitro-grown biofilms and prevented murine Staphylococcus epidermidis implant infection in vivo with slow release of silver ions and limited transient leukocyte cytotoxicity. Furthermore, we describe the biochem. and mol. mechanisms of silver ion action by gene screening and by targeting cell metab. of S. epidermidis at different levels. We demonstrate that silver ions inactivate enzymes by binding sulfhydryl (thiol) groups in amino acids and promote the release of iron with subsequent hydroxyl radical formation by an indirect mechanism likely mediated by reactive oxygen species. This is the first report investigating the global metabolic effects of silver in the context of a therapeutic application. We anticipate that the compds. presented here open a new treatment field with a high medical impact.
    57. 57
      Berchel, M.; Gall, T. L.; Denis, C.; Hir, S. L.; Quentel, F.; Elléouet, C.; Montier, T.; Rueff, J.-M.; Salaün, J.-Y.; Haelters, J.-P.; Hix, G. B.; Lehn, P.; Jaffrès, P.-A. A Silver-Based Metal-Organic Framework Material as a ‘Reservoir’ of Bactericidal Metal Ions. New J. Chem. 2011, 35, 1000– 1003,  DOI: 10.1039/c1nj20202b
      57
      A silver-based metal-organic framework material as a reservoir of bactericidal metal ions
      Berchel, Mathieu; Le Gall, Tony; Denis, Celine; Le Hir, Sophie; Quentel, Francois; Elleouet, Catherine; Montier, Tristan; Rueff, Jean-Michel; Salauen, Jean-Yves; Haelters, Jean-Pierre; Hix, Gary B.; Lehn, Pierre; Jaffres, Paul-Alain
      New Journal of Chemistry (2011), 35 (5), 1000-1003CODEN: NJCHE5; ISSN:1144-0546. (Royal Society of Chemistry)
      The silver-based MOF material Ag3(3-phosphonobenzoate) was evaluated as a bactericidal material. A sustainable release of Ag+, which was quantified by cathodic stripping voltammetry, was responsible for bactericidal activity against the 6 bacterial strains tested.
    58. 58
      Wu, F.; He, D.; Chen, L.; Liu, F.; Huang, H.; Dai, J.; Zhang, S.; You, J. Antibacterial Coordination Polymer Hydrogels Composed of Silver(I)-PEGylated Bisimidazolylbenzyl Alcohol. RSC Adv. 2018, 8, 20829– 20835,  DOI: 10.1039/c8ra00682b
      58
      Antibacterial coordination polymer hydrogels composed of silver(I)-PEGylated bisimidazolylbenzyl alcohol
      Wu, Fang; He, Dengfeng; Chen, Lei; Liu, Fangqin; Huang, Haolong; Dai, Jiangshan; Zhang, Shiyong; You, Jingsong
      RSC Advances (2018), 8 (37), 20829-20835CODEN: RSCACL; ISSN:2046-2069. (Royal Society of Chemistry)
      Herein, antibacterial coordination polymer hydrogels were conveniently fabricated in water via coordination between silver nitrate and PEGylated bisimidazolylbenzyl alc. (1a-c). These coordination polymer hydrogels exhibit much better antibacterial activity than silver nitrate against both Gram-neg. and Gram-pos. pathogens including multidrug-resistant pathogens. The coordination polymer Ag/1c with a long PEG chain (PEG1000) was demonstrated to be the most effective antibacterial material, and its min. inhibition concns. (MICs) could be as low as 15.2 times for common Staphylococcus aureus and 4.8 times for methicillin-resistant Staphylococcus aureus over that of silver nitrate. With improved antibacterial performance, easy prepn. method, improved stability, sustained releasability, outstanding ductility and low cytotoxicity, the as-prepd. coordination polymer hydrogels should find various potential applications such as in clin. burn and wound dressings, biofilms, bioadhesives, and coatings of biomedical materials.

  • Supporting Information

    Supporting Information

    The Supporting Information is available free of charge at https://pubs.acs.org/doi/10.1021/acsami.2c03010.

    • Description of methods and experimental procedures and synthesis of bioCPs 1 and 2, detailed photographs of powders and crystals of 1 and 2, topological representations, photographs of [SBO]n and [PS]n biopolymer films, photographs of doped biopolymer films, particle size distribution analysis, ATR-FT-IR spectra, SEM-EDS data, images of biopolymer coupons in PBS solution, ICP-OES data, water absorption data, antibacterial properties of relevant Ag-based coordination polymers/MOFs, nonnormalized minimum inhibitory radius for different Ag-doped biopolymer films, TGA curves, PXRD patterns, additional antimicrobial data, and crystallographic data in CIF format (CCDC 2055525 and 2055526) (PDF)


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