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Precision Atomistic Structures of Actinium-/Radium-/Barium-Doped Lanthanide Nanoconstructs for Radiotherapeutic Applications
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Precision Atomistic Structures of Actinium-/Radium-/Barium-Doped Lanthanide Nanoconstructs for Radiotherapeutic Applications
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  • Monojoy Goswami
    Monojoy Goswami
    Chemical Sciences Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, United States
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    Orcidhttps://orcid.org/0000-0002-4473-4888
  • Miguel Toro-González
    Miguel Toro-González
    Radioisotope Science & Technology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, United States
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  • Jisue Moon
    Jisue Moon
    Radioisotope Science & Technology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, United States
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  • Sandra Davern*
    Sandra Davern
    Radioisotope Science & Technology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, United States
    *Email: [email protected]
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    Orcidhttps://orcid.org/0000-0003-2755-8912
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ACS Nano

Cite this: ACS Nano 2024, 18, 26, 16577–16588
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https://doi.org/10.1021/acsnano.3c13213
Published June 17, 2024

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Abstract

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Lanthanide vanadate (LnVO4) nanoconstructs have generated considerable interest in radiotherapeutic applications as a medium for nanoscale-targeted drug delivery. For cancer treatment, LnVO4 nanoconstructs have shown promise in encapsulating and retaining radionuclides that emit alpha-particles. In this work, we examined the structure formation of LnVO4 nanoconstructs doped with actinium (Ac) and radium (Ra), both experimentally and using large-scale atomistic molecular dynamics simulations. LnVO4 nanoconstructs were synthesized via a precipitation method in aqueous media. The reaction conditions and elemental compositions were varied to control the structure, fluorescence properties, and size distribution of the LnVO4 nanoconstructs. LnVO4 nanoconstructs were characterized by X-ray diffraction, Raman spectroscopy, and fluorescence spectroscopy. Molecular dynamics simulations were performed to obtain a fundamental understanding of the structure–property relationship between radionuclides and LnVO4 nanoconstructs at the atomic length scale. Molecular dynamics simulations with well-established force field (FF) parameters show that Ra atoms tend to distribute across the nanoconstructs’ surface in a broader coordination shell, while the Ac atoms are arranged inside a smaller coordination shell within the nanocluster. The Ba atoms prefer to self-assemble around the surface. These theoretical/simulation predictions of the atomistic structures and an understanding of the relationship between radionuclides and LnVO4 nanoconstructs at the atomic scale are important because they provide design principles for the future development of nanoconstructs for targeted radionuclide delivery.

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Introduction

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Targeted radionuclide therapy (TRT) has emerged as a promising treatment modality for different types of cancer. (1) Cancer cells die because of a combination of direct, bystander, and systemic responses to radioactive emissions. (2,3) Among these emissions, alpha particles are highly cytotoxic because they induce complex DNA damage, resulting in double-strand breaks. The DNA damage is unrepairable and thus can overcome both radiation and chemotherapy resistance. (3) These characteristics are ideal for cancer treatment when alpha-emitting radionuclides are delivered to cancerous tissue. Alpha-emitting radionuclides are delivered by chemical affinity or by targeting highly expressed tumor antigens with radioimmunoconjugates. (4−8) These approaches are susceptible to the relocation of radionuclides to healthy tissue due to transmetalation and the bond-breaking recoil energy of decay daughters. (2,9−11) To overcome these challenges, multiple approaches have been proposed: a local administration of alpha-emitting radionuclides, rapid uptake of the radioimmunoconjugate by the cell, use of pretargeted radioimmunotherapy, and encapsulating of alpha-emitting radionuclides within nanoconstructs. (10,12) Nanoconstructs offer multiple advantages ranging from the encapsulation of multiple radionuclides and enhanced retention of decay daughters, to the modification of their surface with various functionalities. (13−18) These characteristics make nanoconstructs a promising radionuclide delivery vehicle for TRT.
Among nanoconstructs, lanthanide phosphate and lanthanide vanadate have shown a high encapsulation of [225Ac]Ac3+, [223Ra]Ra2+, and [227Th]Th4+. (13,14,19−24) The retention of their decay daughters─partial or quantitative─was influenced by the nanoconstruct composition and structure. (20,21,23) The composition influences the electron density and, thus, the stopping power of the nanoconstruct as a whole. (25) The structure provides a physical barrier to retain the decay daughters within the nanoconstructs. (20,21,23) As decay daughters can escape the nanoconstruct either by direct ejection during recoil or by leaching owing to lattice damage, (19) the radionuclide’s location within the nanoconstruct influences its retention. (26−29) Experimental validation of the radionuclide’s location is challenging because of length and time scales, limited access to characterization techniques, and finite availability of alpha-emitting radionuclides. While we report several experimental data sets here, wet-lab experiments with radionuclides become extremely difficult due to the very nature of the material properties of alpha-emitting radionuclides. Thus, it becomes imperative to perform in silico experiments of radionuclide nanoconstructs that can predict their structure–property relationship to guide and optimize the performance of wet-lab experiments. Large-scale atomistic molecular dynamics (MD) simulations of nanoconstructs, along with experimental observations, can provide a detailed understanding of these structures at the atomic length scale. MD simulations also contribute to a better understanding of the mechanisms behind enhanced decay daughter retention: dissipation of the recoil energy through atomic displacements and translation within the whole nanoconstruct; (19) and implantation into an adjacent nanoconstruct enhanced by agglomeration. (27) Understanding these mechanisms and their relationships is critical for designing radioactive nanoconstructs in clinical settings.
This work elucidates a fundamental understanding of lanthanide vanadate (LnVO4) nanoconstructs on atomic length and time scales. Experimentally, LnVO4 nanoconstructs were synthesized by precipitation in an aqueous media. Two different LnVO4 nanoconstructs were prepared incorporating either [225Ac]Ac3+ in one or [223Ra]Ra2+ in another, respectively. LnVO4 nanoconstructs doped with surrogate cations were characterized with X-ray diffraction (XRD), Raman spectroscopy, fluorescence spectroscopy, dynamic light scattering (DLS), and transmission electron microscopy (TEM). Radioactive LnVO4 nanoconstructs were characterized by γ-ray and fluorescence spectroscopy. Nanoconstruct characterization was performed to understand the influence of the surrogate/radionuclide concentration on the structure and encapsulation efficiency. The large-scale MD simulations provided an understanding of the structure–property relationships between radionuclides and LnVO4 nanoconstructs using experimentally verified force field parameters. These relationships can help design nanoconstructs for TRT, thereby driving precision nanomedicine and radiotherapy administration to eradicate cancer and minimize side effects.

Results and Discussion

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Crystalline La(1–x)EuxVO4 nanoconstructs were synthesized by precipitation of LnCl3 and Na3VO4 in the presence of 6-AHA (Figure 1a). Nanoconstructs with a molar concentration of Eu below 10% were characterized by a combination of monoclinic and tetragonal structures (Figure 1a and Table S2). Higher Eu molar concentrations (>10%) resulted in the precipitation of nanoconstructs with a tetragonal structure (Figure 1a and Table S2). The changes in the crystal structure of LnVO4 nanoconstructs have been associated with the synthesis method, the reaction pH, and the concentration of lanthanides. The synthesis method affects the nucleation and growth of nanoconstructs and, thus, the formation of different crystal structures. (30−32) The reaction pH determines the form of the vanadium ion and thus the precipitation of compounds with different Ln:V stoichiometry. (33−35) Lastly, the lanthanide ionic radii influence the crystal structure, where small lanthanides (Ln = Ce to Lu) precipitate preferentially with a tetragonal structure. (31,36) Previous research has reported that rapid precipitation of La3+ and Eu3+ with [VO4]3– can result in the formation of nanoconstructs with different crystal structures (i.e., monoclinic LaVO4 and tetragonal EuVO4). (31) For the synthesized La(1–x)EuxVO4 (x < 10%), the decrease in the unit cell parameters (Table S2 and Figure S2a) suggests that Eu3+ cations have entered the structure of LaVO4 rather than precipitated as a secondary phase. (31) The phase transition dependence of La(1–x)EuxVO4 nanoconstructs with Eu3+ concentration was also confirmed by Raman spectroscopy (Figure 1b). The Raman spectra are characterized by two regions corresponding to the tetrahedral [VO4]3– group (700–900 cm–1) and the Ln–O (<500 cm–1) vibrations (Figure 1b). (30,31,37) Increasing the Eu3+ molar concentration within La(1–x)EuxVO4 nanoconstructs changes the characteristic Raman shift for both [VO4]3– and Ln–O vibrations (Figure 1b). These changes in the Raman shift match the phase transition observed with XRD and with other lanthanide vanadate crystals. The size distribution of La(1–x)EuxVO4 nanoconstructs in water was studied by using DLS (Figure 1c). A significant decrease in the hydrodynamic size was observed from LaVO4 (Zave = 295 nm) to EuVO4 (Zave = 37 nm) nanoconstructs. This drastic change in hydrodynamic size could be caused by the change in crystal structure (monoclinic to tetragonal), and thus, the position of lanthanide cations within the nanoconstructs is altered. This position will affect the interaction of lanthanide cations with the carboxylate group of 6-AHA and, thus, influence the growth and stability of the nanoconstructs. There is no clear trend in the hydrodynamic size for intermediate compositions of La and Eu cations within La(1–x)EuxVO4 nanoconstructs (Figure 1c).

Figure 1

Figure 1. (a, d) Diffraction patterns, (b, e) Raman spectra, and (e, f) size distribution of (a–c) La(1–x)EuxVO4 and (d–f) (La0.9Eu0.1)(1–y)BayVO4 of nanoconstructs.

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Lanthanide vanadate nanoconstructs were doped with Ba2+ as a surrogate for [223Ra]Ra2+. (La0.9Eu0.1)(1–y)BayVO4 nanoconstructs were characterized by a tetragonal crystal structure when incorporating up to 25% Ba2+ (Figure 1d). Successful doping of Ba2+ into the La0.9Eu0.1VO4 structure was evidenced by the shift to lower angles of the characteristic peak around 24° (Figure S2b). (38) At a molar concentration of 50% Ba2+, the diffraction pattern changed significantly with respect to the lower concentrations of Ba2+. After performing Rietveld refinement, it was determined that increasing the concentration of Ba2+ within (La0.9Eu0.1)(1–y)BayVO4 nanoconstructs results in a polycrystalline sample. (39) The phases within (La0.9Eu0.1)0.5Ba0.5VO4 nanoconstructs correspond to LaVO4 (space group P121/n1, 72.7%) and Ba2V3O9 (space group P12_1/m1, 27.3%). The fitting of these phases to the diffraction pattern resulted in a χ2 = 7.03, suggesting the model could be reasonable based on the quality of the diffraction pattern (i.e., broad peaks owing to nanoconstruct size). Raman spectra for (La0.9Eu0.1)(1–y)BayVO4 (y = 0, 5, 10, and 25%) matched the characteristic vibrations observed for La(1–x)EuxVO4 nanoconstructs (Figure 1e). In agreement with the XRD patterns, a 50% molar concentration of Ba caused a significant change in the vibrational bands (Figure 1e). No characteristic Ln–O or [VO4]3– vibrations were observed for (La0.9Eu0.1)0.5Ba0.5VO4 nanoconstructs because of the lower level of crystallinity of the sample. The hydrodynamic size of the (La0.9Eu0.1)(1–y)BayVO4 nanoconstructs increased with higher concentrations of Ba (Figure 1f). The increase in size is associated with the precipitation and/or aggregation of nanoconstructs because of a lower concentration of surface lanthanide cations available for complexation with 6-AHA.
The excitation and emission of Eu3+ within La(1–x)EuxVO4 and (La0.9Eu0.1)(1–y)BayVO4 nanoconstructs were studied to assess the influence of dopant ions. Initially, the Eu3+ concentration on La(1–x)EuxVO4 nanoconstructs was varied from 0 to 100%. The excitation spectra were characterized by the charge transfer band (CTB) of the [VO4]3– group (270–350 nm) and the Eu f–f transitions (>350 nm) when using an emission wavelength of 618 nm (Figure 2a). (31,38) The mechanism of luminescence involves: (1) absorption of ultraviolet photons by the [VO4]3– groups, (2) nonradiative transfer to Eu3+ ions, and (3) Eu3+ decay to the ground state by radiative transition. (40) The intensity, shape, and position of the CTB changed with the Eu3+ concentration, whereas only the intensity of the Eu f–f transitions was altered (Figure 2a). A higher CTB intensity, without significant change in location and shape, was obtained when Eu3+ was increased from 2 to 10%. A blue shift of the [VO4]3– CTB was obtained for Eu3+ concentrations greater than 25%. This shift of the [VO4]3– CTB matches the change in crystal structure and the local symmetry of the [VO4]3– group. (38) This change in symmetry causes a shorter distance between Eu3+ and [VO4]3– tetrahedrons and, thus, an increase in overlap between wave functions. (30) The characteristic 5D0 → 7FJ (J = 1, 2, 3, 4) Eu3+ transitions were observed in the emission spectra of La(1–x)EuxVO4 nanoconstructs (Figure 2b). (31,32,38) The intensity of the magnetic dipole transition (5D0 → 7F1, λ = 591 nm) and electric dipole transition (5D0 → 7F2, λ = 618 nm) increased with the Eu3+ concentration up to 50% (Figure 2b). This intensity increase is associated with a greater concentration of emission centers and changes in the crystal structure of La(1–x)EuxVO4 nanoconstructs. (32,38) A change in the crystal structure causes an overlap between wave functions and, thus, higher emission intensity. (30) The intensities of both magnetic and electric dipole transitions were not significantly different for Eu3+ concentrations greater than 50%. This plateau in emission intensity is due to the presence of concentration quenching. (32) An understanding of the Eu3+ environment within the La(1–x)EuxVO4 nanoconstructs is possible by following the emission intensity ratio between the magnetic (5D0 → 7F1, λ = 591 nm) and electric (5D0 → 7F2, λ = 618 nm) dipole transitions as can be observed from Figure 2c. The ratio showed an increase in magnitude from 2 to 10% Eu3+ concentration, followed by a decrease with higher Eu3+ concentrations. This trend is due to the change in crystal structure and a potential concentration quenching effect with an increase in the Eu3+ molar concentration.

Figure 2

Figure 2. Excitation spectra, emission spectra, and emission peak ratio of (a–c) La(1–x)EuxVO4 and (d–f) (La0.9Eu0.1)(1–y)BayVO4 nanoconstructs.

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The concentration of Ba2+ altered the excitation and emission spectra of the (La0.9Eu0.1)(1–y)BayVO4 nanoconstructs, as shown in Figure 2d,e. An increase and red-shift of the [VO4]3– CTB excitation maxima was observed with greater concentrations of Ba2+ (Figure 2d). These changes are associated with the dependence of the [VO4]3– CTB on the lattice parameters. Particularly, a large metal ion such as Ba2+ will cause significant distortions to the structure. (38,39) At 50% Ba2+ concentration, the [VO4]3– CTB intensity decreases significantly because of the change in the crystal structure and crystallinity of the sample (Figure 2d). The emission spectra of (La0.9Eu0.1)(1–y)BayVO4 nanoconstructs were characterized by the 5D0 → 7FJ (J = 1, 2, 3, 4) Eu3+ transitions (Figure 2e). The Eu3+ emission intensity was amplified by increasing the Ba2+ concentration to 25% (Figure 2e). This effect is related to changes in the lattice parameters and the potential introduction of defects and traps. (38,39) The emission intensity decreased significantly when 50% Ba2+ was used (Figure 2e). This decrease is caused by both structural changes (i.e., tetragonal phase has a higher emission than monoclinic) and the potential precipitation of Ba aggregates. (31,38) The intensity ratio between the magnetic and electric dipole transitions did not change significantly with the Ba2+ concentration (Figure 2f).
Doping LaVO4 and La0.9Eu0.1VO4 nanoconstructs with [225Ac]Ac3+ and [223Ra]Ra2+ was performed to assess changes in their encapsulation efficiency and fluorescence spectra. Initial experiments involved the synthesis of LaVO4 and La0.9Eu0.1VO4 nanoconstructs doped with [225Ac]Ac3+ as described in the experimental section. La[225Ac]AcVO4 nanoconstructs had an encapsulation efficiency of 65.4 ± 1.6% (n = 3), whereas 29.1 ± 1.7% (n = 5) was obtained for La0.9Eu0.1[225Ac]AcVO4 nanoconstructs. The encapsulation efficiency of La[225Ac]AcVO4 is similar to that obtained with [144Ce]CeVO4 nanoconstructs with 69.9 ± 7.6% (n = 3). The encapsulation efficiency (65–69%) is expected to be driven by the lower molar concentration of [VO4]3– during synthesis (i.e., 1:0.75 Ln:VO4). The LnCl3, [225Ac]Ac3+, and 6-AHA mixture pH may also play a critical role in the encapsulation efficiency of [225Ac]Ac3+. We observed that adjusting the pH above 7.2 can increase the encapsulation efficiency of [144Ce]Ce3+ above 90%. These results show that the reaction’s pH and, thus, the speciation of [225Ac]Ac3+ and vanadate species determine the encapsulation efficiency within LnVO4 nanoconstructs. The decrease in the [225Ac]Ac3+ encapsulation efficiency within La0.9Eu0.1[225Ac]AcVO4 nanoconstructs may have been influenced by the elemental composition and crystal structure. The difference in activity (i.e., number of [225Ac]Ac3+ moles) may also have played a role in the encapsulation efficiency within nanoconstructs (Table S3). Higher [225Ac]Ac3+ activities (2–50 μCi) were used to synthesize La0.9Eu0.1[225Ac]AcVO4 nanoconstructs because of the characterization with fluorescence spectroscopy (Table S3). Although these results suggest that higher activities result in unstable incorporation of [225Ac]Ac3+ within LnVO4, the reported encapsulation efficiencies are comparable to those obtained with La[225Ac]AcPO4 nanoparticles (47 ± 5%). (19) Woodward et al. used a La/Ac molar ratio of approximately 30,000, (19) which is significantly higher compared to the Ln/Ac molar ratios used in this work (Table S3). Lastly, the lower encapsulation efficiency may have been caused by a decrease in the reaction’s pH due to the higher volume of [225Ac]Ac3+ solution used (i.e., 0.1 M HNO3). As was pointed out previously, maintaining the reaction’s pH above 7 increases the encapsulation efficiency, whereas a slightly acidic pH can decrease the encapsulation efficiency below 50%.
The excitation spectrum of La0.9Eu0.1[225Ac]AcVO4 nanoconstructs was characterized by the CTB of the [VO4]3– group and the Eu f–f transitions when an emission wavelength of 618 nm was used (Figure S3a,b). After the decay of [225Ac]Ac3+ (approximately 3 half-lives), the intensity of the CTB and Eu f–f transitions decreased significantly when using an emission wavelength of 618 nm (Figure S4a,b). These changes could be associated with the distortion and/or damage to the crystal structure caused by the alpha-particle decay. The emission spectrum of La0.9Eu0.1[225Ac]AcVO4 nanoconstructs was characterized by the 5D0 → 7FJ (J = 1, 2, 3, 4) Eu3+ transitions (Figure S3c,d). No significant changes to the Eu3+ transitions were observed after the decay of [225Ac]Ac3+ (Figure S4c,d). These results were expected since [225Ac]Ac3+ is spectroscopically silent due to its electronic structure. (41) However, clear changes in the emission spectra were observed among La0.9Eu0.1VO4, La0.9Eu0.1[225Ac]AcVO4, and decayed La0.9Eu0.1[225Ac]AcVO4 nanoconstructs (Figure 3a,b). First, an emission peak around 440–450 nm corresponding to the 3T1 → 1A1 and 3T2 → lA1 energy transfer of [VO4]3– is more intense in La0.9Eu0.1[225Ac]AcVO4 nanoconstructs compared to that of La0.9Eu0.1VO4 (Figure 3a). (42,43) The emission of [VO4]3– is influenced by lattice defects within the nanoconstructs, (44,45) suggesting that an increase in emission intensity within La0.9Eu0.1[225Ac]AcVO4 nanoconstructs could be attributed to lattice defects. These lattice defects could be caused by [225Ac]Ac3+, its decay daughters, or the radiation damage induced during alpha-particle emission. This radiation damage could be responsible for the increased intensity of this band after the decay of [225Ac]Ac3+ (Figure 3a). Second, La0.9Eu0.1[225Ac]AcVO4 shows a higher 5D0 → 7F4 transition (λ = 700 nm) compared to that of La0.9Eu0.1VO4 nanoconstructs (Figure 3b). This increase in the intensity of the 5D0 → 7F4 transition has been associated with the structural distortion of the EuO8 coordination polyhedron from a cubic geometry to the D2 symmetry. (46,47) It is hypothesized that [225Ac]Ac3+ and decay daughters may cause distortion of the EuO8 coordination polyhedron due to differences in ionic radii. (46−48) This hypothesis is supported by the slight decrease in the intensity of the 5D0 → 7F4 transition after the decay of [225Ac]Ac3+ (Figure 3b). The excitation spectra of La[225Ac]AcVO4 nanoconstructs were characterized by multiple bands depending on the emission wavelength used (Figure S5a). The emission spectrum of La[225Ac]AcVO4 nanoconstructs had an intense band at 450 nm related to the 3T1 → 1A1 and 3T2 → lA1 energy transfer of [VO4]3–. (42,43) Various bands with less intensity were observed in the emission spectrum of La[225Ac]AcVO4 nanoconstructs (Figure S5b). These bands could originate from the defect centers within the nanoconstructs, rather than from the [VO4]3– species. (44) After decay of [225Ac]Ac3+, no significant changes were observed in the excitation spectra (Figure S6a). Although the emission spectra had the characteristic band from [VO4]3– species, the other bands were equivalent to the background (Figure S6b). As was discussed previously, the intensity of the [VO4]3– emission increased after multiple [225Ac]Ac3+ half-lives because of defects caused by radiation damage. (44,45) Overall, these observations show the potential to use La0.9Eu0.1VO4 nanoconstructs and fluorescence spectroscopy to detect and analyze the effects of small concentrations of radionuclides, dopant ions, and potential radiation damage on synthesized nanoconstructs.

Figure 3

Figure 3. (a, b) Emission spectra of La0.9Eu0.1VO4, La0.9Eu0.1[225Ac]AcVO4, and decayed La0.9Eu0.1[225Ac]AcVO4 nanoconstructs. The emission spectra were normalized to the 618 nm peak corresponding to the Eu3+5D0 → 7F2 transition. (c) Emission spectra of La[225Ac]AcVO4 and decayed La[225Ac]VO4 nanoconstructs. The emission spectra were normalized to the 450 nm peak corresponding to the [VO4]3–3T1 → 1A1 and 3T2 → lA1 energy transfer. (d) Encapsulation efficiency of [223Ra]Ra2+ within (La0.9Eu0.1)(1–y)BayVO4 nanoconstructs.

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The encapsulation efficiency of [223Ra]Ra2+ within LaVO4 and La0.9Eu0.1VO4 nanoconstructs synthesized as described in the experimental section was negligible (1.4 ± 1.0%, n = 3). The authors have previously shown that the encapsulation of [223Ra]Ra2+ within LaVO4 and GdVO4 nanoconstructs, prepared by precipitation without 6-AHA, was determined by the synthesis method and reaction conditions. (14,22) Precipitation of La0.9Eu0.1VO4 nanoconstructs at room temperature without 6-AHA resulted in a slight increase in [223Ra]Ra2+ encapsulation efficiency (3.8 ± 0.1%, n = 3). Based on the effect of pH on [223Ra]Ra2+ encapsulation efficiency, (22) NH4OH was added to adjust the pH to approximately 11 during coprecipitation of LaCl3 and Na3VO4 at room temperature. Increasing the pH during LaVO4 nanoconstruct precipitation resulted in a [223Ra]Ra2+ encapsulation efficiency of 98.8 ± 0.5% (n = 3). By adjusting the reaction’s pH to 11, the [223Ra]Ra2+ encapsulation efficiency was increased to 99.1 ± 0.2% (n = 2) when using LaVO4 nanoconstructs synthesized as described in the experimental methods (i.e., with 6-AHA and heated at 90 °C for 30 min). Contrary to the nonradiological experiments, La[223Ra]RaVO4 nanoconstructs synthesized under these conditions (i.e., basic pH) precipitated in deionized water over time. Precipitation of La[223Ra]RaVO4 nanoconstructs could be driven by the suspension’s pH and hence alteration of the zeta potential. An enhancement of the [223Ra]Ra2+ encapsulation efficiency with a pH increase may be associated with the incorporation mechanism. The sorption and complexation of [223Ra]Ra2+ on the nanoconstruct surface has been shown to be the driving force for TiO2 and hydroxyapatite nanoparticles. (49−54) Complexing reactions of [223Ra]Ra2+ with [CO3]2–, [VO4]3–, and OH– could be important under the reaction conditions tested in this work. (52−55) Based on the studies performed with TiO2 and hydroxyapatite, no significant difference was observed between intrinsic and surface incorporation. (51) Although surface incorporation was not studied in this work, it could play a significant role in the encapsulation efficiency of [223Ra]Ra2+ within LnVO4 nanoconstructs. (La0.9Eu0.1)(1–y)BayVO4 nanoconstructs were doped with [223Ra]Ra2+ to understand the effect of nanoconstruct composition on the encapsulation efficiency. The [223Ra]Ra2+ encapsulation efficiency was greater than 90% for the different Ba2+ concentrations (Figure 3d). The mean [223Ra]Ra2+ encapsulation efficiency decreased from 98.2 ± 0.5% (n = 3) to 92.8 ± 7.3% (n = 3) for La0.9Eu0.1VO4 and (La0.9Eu0.1)0.5Ba0.5VO4 nanoconstructs, respectively. A decrease in [223Ra]Ra2+ encapsulation efficiency could be associated with the competition with Ba2+ for sites within the La0.9Eu0.1VO4 nanoconstruct. Previous research has shown that a low [223Ra]Ra2+ encapsulation efficiency is associated with competing impurities and nonspecific sorption. (50) Based on surrogate studies, the high encapsulation efficiencies obtained could be explained by the precipitation of [223Ra]Ra2+/Ba2+ as a secondary phase (Figure 1d). Previous research has studied the in vitro stability of Ln[223Ra]RaVO4 nanoconstructs. The stability of Ln[223Ra]RaVO4 was influenced by the type of radionuclide, the reaction conditions, and the dialysis buffer. (14,22) These results suggest that the complexation of [225Ac]Ac3+ and [223Ra]Ra2+ on the LnVO4 surface is critical for nanoconstruct stability. Because of limitations in handling radioactive samples, modeling and simulation of LnVO4 nanoconstructs doped with [225Ac]Ac3+ and [223Ra]Ra2+ are required to understand their formation and radionuclide-structure interaction.
From the discussion in the method section, it has been shown that the simulation results of pure lanthanide match fairly well with the experimental findings of pristine LnVO4 nanoconstructs (Figure 7), and the liquid water structure within the nanoconstruct (Figure S1). Relying on these experimentally verified lanthanide simulations and previously reported FF parameters, atomistic MD simulations were performed by introducing three different dopant ions: Ac3+, Ba2+, and Ra2+ for the three different simulation systems. Two dopant ion concentrations were used, 3 mol % for Ac3+ and Ra2+ and 25 mol % for Ba2+, to ensure that the simulations were commensurate with experimental conditions. All the simulations for (1) Ac–La0.9Eu0.1VO4, (2) Ba–La0.9Eu0.1VO4, and (3) Ra–La0.9Eu0.1VO4 were equilibrated for 2 ns in aqueous solution at 67 °C, which is close to the experimental conditions, with subsequent cooling of the nanoconstructs to ambient temperature, T = 27 °C. Once the equilibration was achieved, the statistical average of the structural properties was obtained from a 0.5 ns simulation within the last 200 ps trajectory. For the low-temperature systems (T = 27 °C) the Ac/Ra systems' statistical properties were obtained from 1 ns simulation, and the structural properties were obtained from the last 200 ps trajectory.
Figure 4 shows the Ac–Ln and Ra–Ln structural properties as obtained from radial distribution function (RDF) calculations at 3.0 mol % of Ac/Ra. Figure 4a–c shows the RDF at T = 67 °C, and Figure 4d–g shows the simulation snapshot at the end of 500 ps production runs after equilibrating for 2 ns. From the snapshots, the Ac–Ln structures exhibit larger, connected percolated clusters (Figure 4d), while the Ra–Ln clusters are smaller, separated, and spread across the simulation box (Figure 4e). This result suggests that Ra–Ln can potentially form smaller nanoconstructs, which is highly relevant for radiotherapy applications. These structures exhibit excellent stability as after cooling down the structures to T = 27 °C, the RDF does not show any difference as shown in Figure S2. The structural stability is a result of strong Coulombic interactions between charged atoms that allow oppositely charged atoms to strongly adhere to each other due to electrostatics overtaking entropic forces between the charged atoms. The stable structure can also be seen from the simulation snapshots shown in Figures S3 and S4.

Figure 4

Figure 4. Structural details of Ac–Ln and Ra–Ln nanoconstructs at 3 mol % of Ac/Ra doping at 67 °C. Three different RDFs, Ac/Ra–O, La–O, and Eu–O are shown for the (a) Ac–Ln system and (b) Ra–Ln system. The comparison between Ac–O and Ra–O are shown in (c). Colors are represented in the legends. (d, e) Simulation snapshots of Ac–O and Ra–O systems, respectively. Water molecules are not shown for clarity. (f, g) Closeup of the nanoconstructs for Ac–O and Ra–O systems, respectively. Color scheme in the snapshots: Ac/Ra─blue, La─cyan, Eu─yellow, V─green, and O─red. The low-temperature, T = 27 °C, RDFs are compared in Figure S2 showing structural stability of the nanoconstructs.

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The positions of the peaks between the electropositive Ra2+/Ac3+ and the electronegative oxygen atoms from VO4 are representative of the relative positions of two oppositely charged ions inside the nanoconstruct. Because these oppositely charged atoms are attracted by strong electrostatic interactions, the RDFs show close proximity of the positions of respective atoms inside these nanoconstructs. In Figures 4 a–c, both the Ra- and Ac-doped nanoconstructs show that Eu–O (red) and La–O (green) have a similar peak and short-range ordering until approximately 8 Å. The RDFs of Ac–O and Ra–O (black) exhibit a closer first peak for Ac–O with respect to that of Ra–O (Figure 4c). The first peak of Ac–O is at 2.35 Å and at 2.65 Å for Ra–O with coordination numbers of 7.1 and 8.5, respectively. These structural positions and coordination numbers, especially for Ra2+ nanoconstructs, are found to be smaller than what is observed in Ra2+ structures in the chelator-stabilized crystal structure of Ra2+. (56) This is because these inorganic nanoconstructs are stabilized as part of a lanthanide inorganic lattice rather than through coordination within a chelator. Furthermore, the first peak height of Ac–O is more than double than that of the Ra–O first peak height, exhibiting stronger Ac atom agglomeration with shorter separation within the nanoconstruct compared to the Ra atoms that exhibit weaker aggregation with larger separation distances. This Ra atom structural behavior inside the cluster represents Ra atom distribution near the surface of the nanoconstructs. The higher coordination number in Ra–O (8.5) compared with that of the Ac–O (7.1) means that the Ra atoms are distributed in a broader coordination shell compared to the Ac atoms within the cluster. The same can be seen from the broader peak widths in Ra–O compared to Ac–O (Figure 4c). These structural results elucidate the fact that the Ra atoms tend to reside on the surface of the nanoconstructs, while the Ac atoms are distributed inside the core of the clusters. (57) From the structural analysis, we infer that the emitted α particle dose would be higher from the Ra-doped lanthanide due to the Ra distribution on the periphery of the nanoconstructs. However, a near-surface, peripheral distribution of the Ra can also be disadvantageous due to the release of decay daughters that would not occur in the core-placed Ac atom in the Ac-doped lanthanide nanoconstruct.
To understand the effect of a high level of radionuclide doping in lanthanide nanoconstructs, we investigated the structures of 25 mol % of Ba/Ra doping within the lanthanide nanoconstruct following the same simulation techniques. The structures at 67 °C from the simulation snapshots of these nanoconstructs are shown in Figure 5a–d. As seen before in 3 mol % systems, the Ra-doped nanoconstructs show smaller cluster sizes compared with Ba-doped nanoconstructs. The Ba–Ln nanoconstructs percolated all over the system, while the Ra-doped nanoconstructs show the distribution of a smaller cluster spanning the whole simulation box.

Figure 5

Figure 5. Structures of 25 mol % Ba/Ra doped lanthanide nanoconstructs. (a, b) Simulation snapshots of Ba- and Ra-doped nanoconstructs. (c, d) Closeup of Ba- and Ra-doped nanoclusters. Color scheme of the snapshots: Ba/Ra─blue, La─yellow, Eu─purple, V─green, and O─red. Water molecules are not shown for clarity. (e, f) RDF of metallic cations with the oxygen of vanadates for Ba- and Ra-doped nanoconstructs. (g) Comparison of RDFs between Ba- and Ra-doped nanoconstructs.

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Ra atoms were observed to be preferentially distributed on the surface of the nanoconstructs, while both Ac and Ba clusters were located inside the cores of the nanoconstructs. The van der Waals radii of Ac, Ba, and Ra are 2.00 2.68, and 2.83 Å, respectively. This suggests that the largest Ra atoms may rearrange themselves on the nanoconstruct surface due to the excluded volume effect of the Ra atoms as observed in different structurally stable materials. (58,59) This explains why we consistently observed Ra first peak positions to be the highest compared to Ac and Ba from the oxygen atoms of vanadate, representing a higher agglomeration of Ra atoms compared to Ac and Ba.
The mean-square displacement (MSD) of the Ac and Ra atoms was monitored to obtain a dynamic perspective of the evolution of these nanoconstructs and the stability of the atoms within the nanoconstructs. The MSD was calculated from the last 1 ns production runs, and is defined by, MSD=1N∑i=1N|ri(t)−ri(0)|2, where ri(t) and ri(0) are the positions of the atoms at time t, and N is the total number of atoms. The MSDs are listed in Figure 6. For all the cases, a slower MSD of Ac/Ra (blue) and Eu (red) ions compared to La (black) was observed. The Ac/Ra and Eu atoms are electrostatically strongly bound to the nanoconstructs that move with the larger cluster, and hence slow motion (lower MSDs). On the contrary, while many of the La ions are strongly bound to the nanoconstruct, a large number of La atoms stay free in the solvent as observed in the simulation and also in experiments. The freely moving La atoms are responsible for the faster dynamics (larger MSD) for La atoms. For two different systems (Figure 6e), Ac–Ln and Ra–Ln, while Ac and Ra both hold tightly together inside the lanthanide nanoconstruct, Ra atoms show faster MSD values (blue) than Ac atoms (black), indicating faster motion in Ra atoms. The faster motion of the Ra atoms is due to their outer shell distribution that provides higher freedom of movement, as described in Figure 4, while the motions of the Ac atoms were adversely affected by their distribution inside the core of the nanoconstruct, which results in slower motion. The temperature dependence of the MSDs (Figure 6f) exhibits no substantial differences in La atom MSDs and the freedom of motion of free La atoms is not affected by lowering the temperature from 67 to 27 °C. However, electrostatically bound Ac/Ra and Eu atoms show slightly slower MSDs at 27 °C (solid line) than at 67 °C due to entropic effects. The evolution of these Ac–Ln and Ra–Ln nanoconstructs at high temperatures (T = 67 °C) and after cooling to 27 °C are shown in Figures S3 and S4 which, along with the dynamical data in Figure 6, reiterates the stability of these nanoconstructs upon cooling from high temperature as discussed in the structural analysis.

Figure 6

Figure 6. Mean-square-displacement (MSD) of La, Eu, and Ac/Ra of Ac-doped Ln (a,c) and Ra-doped Ln (b,d) compared with La and Eu atoms of the lanthanides. Low- and high-temperature MSDs are shown in (a), (b) at T = 27 °C, and (c), (d) at T = 67 °C respectively. A comparison of Eu (red and magenta), Ac (black), and Ra (blue) MSDs for Ac–Ln and Ra–Ln systems is shown in (e). Comparison with respect to temperature for these two systems is shown in (f); the solid lines are for T = 27 °C, and dashed lines are for T = 67 °C. MSD is lower at higher temperatures.

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Conclusions

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In conclusion, this study has developed fundamental structural information for several different lanthanide nanoconstructs with three different radionuclides, actinium, barium, and radium, using experiments and large-scale MD simulations. Structural properties of lanthanide nanoconstructs were observed with different concentrations of Ac, Ba, and Ra as dopants. The detailed crystalline structure of nanoconstructs with Ra dopants is especially difficult to achieve experimentally because of the limited availability of radionuclides and the associated radiological hazards. This work showed by simulations the structural details and position of the Ac/Ba/Ra atoms within the LnVO4 nanoconstructs. The La0.9Eu0.1VO4 nanoconstructs doped with [225Ac]Ac3+ and [223Ra]Ra2+ were synthesized via precipitation in aqueous media. Encapsulation of 225Ac was determined by the preparation methods, i.e., nanoconstruct composition and crystal structure. The nanoconstruct composition had no significant effect on the encapsulation of [223Ra]Ra2+. The encapsulation of [223Ra]Ra2+ was however dependent on the reaction’s pH. Both LaVO4 and La0.9Eu0.1VO4 nanoconstructs showed additional emission peaks after doping with [225Ac]Ac3+. Molecular dynamics simulations show atomistic details of the structure–property relationship of Ac-, Ba-, and Ra-doped LnVO4 nanoconstructs at different mol % of dopant ions. The structural properties of Ac/Ba show that they tend to agglomerate inside the nanoconstructs, while the Ra atoms tend to arrange near the surface of the nanoconstructs. Similar structural properties were observed in the experiments with different mole percents of Ac and Ra dopant ions within the lanthanide nanoconstructs. Although experiments with radionuclides are difficult to perform in a wet lab setting because of the associated radioactive hazards, large-scale simulations, such as those presented in this work, can provide a priori structural details of radioactive LnVO4 nanoconstructs, which, in turn, can be corroborated with fewer experiments. Therefore, these experiments and simulations provide structural details and indicate the position of radionuclides within the LnVO4 nanoconstructs. This information is necessary to enhance the drug development process by aiding the design principles of future nanoconstructs for TRT. The application of targeted nanomedicines for cancer radiotherapy is currently evolving, and soon, will have the potential to become a critical component for cancer radiotherapy to treat drug-resistant and metastatic disease.

Methods

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Experimental Section

Materials

The chemicals lanthanum(III) chloride heptahydrate (LaCl3·7H2O; American Chemical Society reagent, Sigma-Aldrich, Chemical Abstracts Service [CAS] 10025-84-0), europium(III) chloride heptahydrate (EuCl3·6H2O; American Chemical Society reagent, Sigma-Aldrich, CAS 13759-92-7), barium nitrate (Ba(NO3)2; >99%, Acros Organics, CAS 10022-31-8), 6-aminohexanoic acid (6-AHA; >98.5%, Sigma-Aldrich, CAS 60-32-2), sodium orthovanadate (Na3VO4; 99%, Acros Organics, CAS 13721-39-6), and an ammonia solution (NH4OH; 28–30%, Sigma-Aldrich, CAS 1336-21-6) were used without further purification. Deionized water (18 Ω·cm) was obtained from a MilliporeSigma Milli-Q Ultrapure Water System.
The radionuclide [225Ac]Ac3+ (t1/2 = 9.9 days) was obtained from a thorium generator (228Th, 229Th, and 232Th) at the Oak Ridge National Laboratory after various chemical separation processes involving anion and cation exchange chromatography. (60) The radionuclide [223Ra]Ra2+ (t1/2 = 11.4 d) was obtained from 227Ac generated via the thermal neutron irradiation of a 226Ra target following the processing and purification steps described elsewhere. (22) Both [225Ac]Ac3+ and [223Ra]Ra2+ were dissolved in 0.1 M HNO3 for the nanoconstruct synthesis.

Nanoparticle Synthesis

Lanthanide vanadate (La(1–x)EuxVO4) nanoconstructs were synthesized by adapting the procedures reported by Huignard et al. (40,61) Different Eu3+ molar concentrations (e.g., Eu3+ = 0, 2, 5, 10, 25, 50, 75, and 100%) were used to synthesize La(1–x)EuxVO4 nanoconstructs and evaluate their fluorescent properties, size distribution, and crystal structure. Similarly, (La0.9Eu0.1)(1–y)BayVO4 nanoconstructs were synthesized with different Ba2+ molar concentrations (e.g., Ba2+ = 0, 5, 10, 25, and 50%) as a surrogate for [223Ra]Ra2+. The La(1–x)EuxVO4 and (La0.9Eu0.1)(1–y)BayVO4 were synthesized by precipitation of metal salts (i.e., LaCl3, EuCl3, and Ba(NO3)2) with Na3VO4 in the presence of 6-AHA to control their size and to increase their stability in water. For synthesis, metal salts, 6-Aminohexaonic Acid (6-AHA), and Na3VO4 were dissolved in deionized (DI) water at a concentration of 0.1 M, mixed in a 1:0.75:0.75 molar ratio, and then heated at 90 °C for 30 min. Nanoconstruct suspensions were washed at least three times by centrifugation (14,000–15,000 rpm, 15 min) and resuspended in deionized water. The La(1–x)EuxVO4 and (La0.9Eu0.1)(1–y)BayVO4 doped with 225Ac or 223Ra were prepared following the same steps described previously after mixing the metal salts with each radionuclide solution. The precipitation of LnVO4 nanoconstructs without 6-AHA under basic conditions and at room temperature was also explored. (40)

Characterization

The La(1–x)EuxVO4 and (La0.9Eu0.1)(1–y)BayVO4 nanoconstruct suspensions were diluted in DI water to assess their particle size distribution and fluorescence properties. Particle size distribution was obtained using DLS in a Malvern Zetasizer Nano ZS. The reported hydrodynamic size (Zave) and polydispersity index (PdI) correspond to the mean of three runs with at least 10 measurements, each as defined in the standard operating procedure. Excitation and emission spectra were collected using a Fluorolog-QM spectrometer (Horiba) by diluting nanoconstruct suspensions in DI water. The excitation was measured with a 100-W pulsed xenon lamp as the source. The morphology of La0.9Eu0.1VO4 nanoconstructs was characterized by TEM using a JEOL NEOARM TEM/STEM. A diluted nanoconstruct suspension was drop-cast onto a carbon-Formvar Cu grid and evaporated to dryness at room temperature. The La(1–x)EuxVO4 and (La0.9Eu0.1)(1–y)BayVO4 nanoconstruct suspensions were precipitated by centrifugation and then evaporated to dryness in a muffle furnace at 60 °C. Nanoconstruct precipitates were ground using a mortar and pestle to obtain a fine powder. These powders were characterized using a PANanalytical X’Pert Pro MPD X-ray diffractometer. Rietveld analysis of the XRD data was performed using GSAS II software. (62,63) Raman spectra were recorded by using a Renishaw in Via Qontor confocal Raman microscope with a 532 nm laser. The sample was analyzed at an optical magnification of 20×. Radionuclide activities were determined by γ-ray spectroscopy using a high-purity germanium (HPGe) detector coupled to a PC-based multichannel analyzer (Canberra Industries, Meriden, CT). The HPGe has a crystal active volume of approximately 100 cm3 and a beryllium window. Energy and efficiency calibrations were determined by γ-ray sources traceable to the National Institute of Standards and Technology. The encapsulation efficiency of 225Ac and 223Ra was determined by measuring the nanoconstruct suspension and supernatant after washing them as described previously.

Molecular Dynamics Simulations

The atomistic MD simulations are performed using the Large-scale Atomic/Molecular Massively Parallel Simulator (LAMMPS) molecular dynamics package. (64) The initial system was built using randomly distributed individual lanthanum (La), europium (Eu), and vanadate (VO4) ions in a box of 40 nm3 using the Packmol package. (65) The first set of simulations was developed to obtain the structural properties of pure lanthanides (Ln) without the addition of any radionuclides as a control system to compare directly with experiments. Subsequently, three different systems were studied to understand the atomistic structures of Ac, Ba, and Ra with respect to the La, Eu, and O (of VO4) within the lanthanide nanoclusters. The whole system was placed in an aqueous environment within a box of water with a density of 1 g/cm3. This creates three different systems of dilute solutions of lanthanide salt atoms with three different radioactive dopant ions: Ac, Ba, and Ra.
The interaction potentials or force field (FF) parameters between different atomic species were used as follows. For the lanthanide cations (La, Eu), additive Chemistry at Harvard Molecular Mechanics (CHARMM) FF was used to model van der Waals interactions because it shows excellent agreement with experiments. (66) The interaction of VO4 ions in the solvation state was modeled using AMBER FF following past work that has shown excellent agreement with experiments. (67) For the water molecules, the SPC/E water model was used for all the simulations. Electrostatic interactions between all charged ions and partially charged oxygen and hydrogen of water were used. The randomly generated initial system was generated at 0 °C as shown in Figure 7a. The temperature was subsequently increased to the experimental temperature, 67 °C. At T = 67 °C the system was equilibrated for 2 ns to form nanoclusters, as shown in Figure 7b. Once the system was equilibrated at a high temperature, the system was then cooled to ambient temperature, T = 27 °C. The final configuration of the cooled state is shown in Figure 7c. This result compares well with those of lanthanide clusters observed in TEM experiments (Figure 7d). For a pristine lanthanide nanoconstruct suspension, the structures of different ionic species with respect to their counterpart and the structure of water molecules are investigated using radial distribution functions (RDFs), as shown in Figure S1. The oxygen–oxygen, oxygen–hydrogen, and hydrogen–hydrogen RDFs (68) and lanthanide ions RDFs suggest that the performance of the model system and FF parameters are overall excellent to provide confidence in simulation data. The radionuclides, Ac, Ra, and Ba, interactions with water and lanthanides are modeled using experimentally verified Lennard–Jones (LJ) potential, and the electrostatic interactions of the charged particles are modeled using Coulomb potential. (69) The Ac/Ra/Ba LJ interaction parameters are tabulated in Table S1. For further details of the simulation methods, please see the Supporting Information (SI).

Figure 7

Figure 7. Lanthanide vanadate simulations in an aqueous environment. (a) Initial system setup containing La, Eu, and VO4 ions in g/cm3 water randomly distributed in a box of 40 nm3. (b) 3D structure of the Ln nanoconstruct at experimental temperature, 67 °C. Water molecules are not shown for clarity. (c) Top view (2D) snapshot of the lanthanide nanoconstruct as can be observed from the TEM of experimentally prepared nanoconstructs. The background dots are neutral La atoms that stay mostly in water in a solvated state. (d) TEM nanoconstruct of lanthanide vanadate showing a similar structure to that derived in (c).

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Supporting Information

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The Supporting Information is available free of charge at https://pubs.acs.org/doi/10.1021/acsnano.3c13213.

  • Description of MD simulations in detail; force-field parameters (Lennard-Jones) used in the MD simulations; RDF of water in LnVO4 and the comparison of the RDF of La, Eu, and oxygen of VO4; RDF of Ac-/Ra-doped lanthanide at different temperatures and the snapshots; Rietveld analysis parameters and XRD patterns; summary of the molar ratio of the nanoconstructs; excitation and emission spectra of 225Ac-doped nanoconstructs and 30 days' decayed 225Ac-doped nanoconstructs, respectively; and different compositions of lanthanides (PDF)

Terms & Conditions

Most electronic Supporting Information files are available without a subscription to ACS Web Editions. Such files may be downloaded by article for research use (if there is a public use license linked to the relevant article, that license may permit other uses). Permission may be obtained from ACS for other uses through requests via the RightsLink permission system: http://pubs.acs.org/page/copyright/permissions.html.

Author Information

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  • Corresponding Author
  • Authors
    • Monojoy Goswami - Chemical Sciences Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, United States;  Orcidhttps://orcid.org/0000-0002-4473-4888
    • Miguel Toro-González - Radioisotope Science & Technology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, United States
    • Jisue Moon - Radioisotope Science & Technology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, United States
  • Notes
    The authors declare no competing financial interest.

Acknowledgments

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This research was supported by the US Department of Energy’s (DOE’s) Oak Ridge National Laboratory Directed Research & Development (LDRD) Program. The isotopes used in this research was supplied by the U.S. Department of Energy Isotope Program, managed by the Office of Isotope R&D and Production. The MD simulations used resources of the Oak Ridge Leadership Computing Facility at Oak Ridge National Laboratory, which is supported by the DOE Office of Science of the U.S. DOE under Contract No. DE-AC05-00OR22725. Part of the MD simulations used resources of the National Energy Research Scientific Computing Center (NERSC), a DOE Office of Scientific User Facility supported by the DOE Office of Science under Contract No. DE-AC02- 05CH11231. The authors thank Christopher Orosco from ORNL’s Creative Services Communications Division for designing the Supplementary Cover Image for this work.

Abbreviations

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6-AHA

6-aminohexanoic acid

CAS

chemical abstracts service

CTB

charge-transfer band

DI

deionized

DLS

dynamic light scattering

FF

force field

MD

molecular dynamics

RDF

radial distribution function

TEM

transmission electron microscopy

TRT

targeted radionuclide therapy

XRD

X-ray diffraction

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    PURPOSE: The humanized monoclonal antibody, trastuzumab (Herceptin), directed against HER2/neu, has been effective in the treatment of breast cancer malignancies. However, clin. activity has depended on HER2/neu expression. Radiolabeled trastuzumab has been considered previously as a potential agent for radioimmunotherapy. The objective of this study was to investigate the efficacy of trastuzumab labeled with the α-particle emitting at. generator, actinium-225 (225Ac), against breast cancer spheroids with different HER2/neu expression levels. 225Ac has a 10-day half-life and a decay scheme yielding four α-particles. Exptl. Design: The breast carcinoma cell lines MCF7, MDA-MB-361 (MDA), and BT-474 (BT) with relative HER2/neu expression (by flow cytometry) of 1:4:18 were used. Spheroids of these cell lines were incubated with different concns. of 225Ac-trastuzumab, and spheroid growth was measured by light microscopy over a 50-day period. RESULTS: The activity concn. required to yield a 50% redn. in spheroid vol. at day 35 was 18.1, 1.9, and 0.6 kBq/mL (490, 52, 14 nCi/mL) for MCF7, MDA, and BT spheroids, resp. MCF7 spheroids continued growing but with a 20-30 day growth delay at 18.5 kBq/mL. MDA spheroid growth was delayed by 30-40 days at 3.7 kBq/mL; at 18.5 kBq/mL, 12 of 12 spheroids disaggregated after 70, days and cells remaining from each spheroid failed to form colonies within 2 wk of being transferred to adherent dishes. Eight of 10 BT spheroids failed to regrow at 1.85 kBq/mL. All of the BT spheroids at activity concns. 3.7 kBq/mL failed to regrow and to form colonies. The radiosensitivity of these three lines as spheroids was evaluated as the activity concn. required to reduce the treated to untreated spheroid vol. ratio to 0.37, denoted DVR37. An external beam radiosensitivity of 2 Gy was found for spheroids of all three of the cell lines. After α-particle irradn. a DVR37 of 1.5, 3.0, and 2.0 kBq/mL was detd. for MCF7, MDA, and BT, resp. CONCLUSION: These studies suggest that 225Ac-labeled trastuzumab may be a potent therapeutic agent against metastatic breast cancer cells exhibiting intermediate to high HER2/neu expression.
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    Allen, B. J.; Huang, C.-Y.; Clarke, R. A. Targeted Alpha Anticancer Therapies: Update and Future Prospects. Biol. Targets Ther. 2014, 8, 255– 267,  DOI: 10.2147/BTT.S29947
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    Feuerecker, B.; Biechl, P.; Seidl, C.; Bruchertseifer, F.; Morgenstern, A.; Schwaiger, M.; Eisenreich, W. Diverse Metabolic Response of Cancer Cells Treated with a 213 Bi-Anti-EGFR-Immunoconjugate. Sci. Rep. 2021, 11, 6227,  DOI: 10.1038/s41598-021-84421-4
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    Song, H.; Hobbs, R. F.; Vajravelu, R.; Huso, D. L.; Esaias, C.; Apostolidis, C.; Morgenstern, A.; Sgouros, G. Radioimmunotherapy of Breast Cancer Metastases with α-Particle Emitter 225Ac: Comparing Efficacy with 213 Bi and 90Y. Cancer Res. 2009, 69, 8941– 8948,  DOI: 10.1158/0008-5472.CAN-09-1828
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    Eychenne, R.; Chérel, M.; Haddad, F.; Guérard, F.; Gestin, J. F. Overview of the Most Promising Radionuclides for Targeted Alpha Therapy: The “Hopeful Eight.. Pharmaceutics 2021, 13, 906,  DOI: 10.3390/pharmaceutics13060906
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    Overview of the most promising radionuclides for targeted alpha therapy: the "hopeful eight"
    Eychenne, Romain; Cherel, Michel; Haddad, Ferid; Guerard, Francois; Gestin, Jean-Francois
    Pharmaceutics (2021), 13 (6), 906CODEN: PHARK5; ISSN:1999-4923. (MDPI AG)
    Among all existing radionuclides, only a few are of interest for therapeutic applications and more specifically for targeted alpha therapy (TAT). From this selection, actinium-225, astatine-211, bismuth-212, bismuth-213, lead-212, radium-223, terbium-149 and thorium-227 are considered as the most suitable. Despite common general features, they all have their own phys. characteristics that make them singular and so promising for TAT. These radionuclides were largely studied over the last two decades, leading to a better knowledge of their prodn. process and chem. behavior, allowing for an increasing no. of biol. evaluations. The aim of this review is to summarize the main properties of these eight chosen radionuclides. An overview from their availability to the resulting clin. studies, by way of chem. design and preclin. studies is discussed.
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    de Kruijff, R. M.; Wolterbeek, H. T.; Denkova, A. G. A Critical Review of Alpha Radionuclide Therapy─How to Deal with Recoiling Daughters?. Pharmaceuticals 2015, 8, 321– 336,  DOI: 10.3390/ph8020321
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    A critical review of alpha radionuclide therapy-how to deal with recoiling daughters?
    de Kruijff, Robin M.; Wolterbeek, Hubert T.; Denkova, Antonia G.
    Pharmaceuticals (2015), 8 (2), 321-336CODEN: PHARH2; ISSN:1424-8247. (MDPI AG)
    This review presents an overview of the successes and challenges currently faced in alpha radionuclide therapy. Alpha particles have an advantage in killing tumor cells as compared to beta or gamma radiation due to their short penetration depth and high linear energy transfer (LET). Touching briefly on the clin. successes of radionuclides emitting only one alpha particle, the main focus of this article lies on those alpha-emitting radionuclides with multiple alpha-emitting daughters in their decay chain. While having the advantage of longer half-lives, the recoiled daughters of radionuclides like 224Ra (radium), 223Ra, and 225Ac (actinium) can do significant damage to healthy tissue when not retained at the tumor site. Three different approaches to deal with this problem are discussed: encapsulation in a nano-carrier, fast uptake of the alpha emitting radionuclides in tumor cells, and local administration. Each approach has been shown to have its advantages and disadvantages, but when larger activities need to be used clin., nano-carriers appear to be the most promising soln. for reducing toxic effects, provided there is no accumulation in healthy tissue.
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    Merkx, R. I. J.; Rijpkema, M.; Franssen, G. M.; Kip, A.; Smeets, B.; Morgenstern, A.; Bruchertseifer, F.; Yan, E.; Wheatcroft, M. P.; Oosterwijk, E.; Mulders, P. F. A.; Heskamp, S. Carbonic Anhydrase IX-Targeted α-Radionuclide Therapy with 225Ac Inhibits Tumor Growth in a Renal Cell Carcinoma Model. Pharmaceuticals 2022, 15, 570,  DOI: 10.3390/ph15050570
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    Membreno, R.; Cook, B. E.; Zeglis, B. M. Pretargeted Radioimmunotherapy Based on the Inverse Electron Demand Diels-Alder Reaction. J. Vis. Exp. 2019, 2019, 59041  DOI: 10.3791/59041
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    Toro-González, M.; Dame, A. N.; Mirzadeh, S.; Rojas, J. V. Gadolinium Vanadate Nanocrystals as Carriers of α-Emitters (225Ac, 227Th) and Contrast Agents. J. Appl. Phys. 2019, 125, 214901  DOI: 10.1063/1.5096880
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    Gadolinium vanadate nanocrystals as carriers of α-emitters (225Ac, 227Th) and contrast agents
    Toro-Gonzalez, Miguel; Dame, Ashley N.; Mirzadeh, Saed; Rojas, Jessika V.
    Journal of Applied Physics (Melville, NY, United States) (2019), 125 (21), 214901/1-214901/11CODEN: JAPIAU; ISSN:0021-8979. (American Institute of Physics)
    Gadolinium vanadate (GdVO4) core and core + 2 shell nanocrystals (NCs) were evaluated for in vitro retention of 225Ac, 227Th, and their first decay daughters, 221Fr and 223Ra, resp. GdVO4 NCs with a tetragonal crystal system (zircon-type) and spherical morphol. were obtained by pptn. of GdCl3 and Na3VO4 using sodium citrate as a complexing agent. The growth of two nonradioactive GdVO4 shells on both Gd(225Ac)VO4 and Gd(227Th)VO4 core NCs was demonstrated by an increase of 0.7 nm and 2 nm in the crystallite size, resp. The max. leakage of 225Ac was 15% and 2.4% from core and core + 2 shells, whereas the leakage of 227Th was 3% and 1.5%, resp. The presence of two nonradioactive GdVO4 shells increased the retention of 221Fr and 223Ra by 20% and 15% with respect to core NCs. Furthermore, a longitudinal proton relaxivity, r1 = 0.9289 s-1 mM-1, confirmed their potential application as contrast agents for magnetic resonance imaging. In summary, GdVO4 NCs show promising capabilities as radionuclide carriers with partial retention of decay daughters and as contrast agents for theranostic applications. (c) 2019 American Institute of Physics.
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    Toro-González, M.; Dame, A. N.; Mirzadeh, S.; Rojas, J. V. Encapsulation and Retention of 225Ac, 223Ra, 227Th, and Decay Daughters in Zircon-Type Gadolinium Vanadate Nanoparticles. Radiochim. Acta 2020, 108, 967– 977,  DOI: 10.1515/ract-2019-3206
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    Tao, Y.; Sun, Y.; Shi, K.; Pei, P.; Ge, F.; Yang, K.; Liu, T. Versatile Labeling of Multiple Radionuclides onto a Nanoscale Metal–Organic Framework for Tumor Imaging and Radioisotope Therapy. Biomater. Sci. 2021, 9, 2947– 2954,  DOI: 10.1039/D0BM02225J
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    Tanahashi, K.; Mikos, A. G. Effect of Hydrophilicity and Agmatine Modification on Degradation of Poly(Propylene Fumarate-Co-Ethylene Glycol) Hydrogels. J. Biomed. Mater. Res. Part A 2003, 67A, 1148– 1154,  DOI: 10.1002/jbm.a.10147
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    Sanità, G.; Carrese, B.; Lamberti, A. Nanoparticle Surface Functionalization: How to Improve Biocompatibility and Cellular Internalization. Front. Mol. Biosci. 2020, 7, 587012  DOI: 10.3389/fmolb.2020.587012
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    Nanoparticle surface functionalization: how to improve biocompatibility and cellular internalization
    Sanita, Gennaro; Carrese, Barbara; Lamberti, Annalisa
    Frontiers in Molecular Biosciences (2020), 7 (), 587012CODEN: FMBRBS; ISSN:2296-889X. (Frontiers Media S.A.)
    A review. The use of nanoparticles (NP) in diagnosis and treatment of many human diseases, including cancer, is of increasing interest. However, cytotoxic effects of NPs on cells and the uptake efficiency significantly limit their use in clin. practice. The physico-chem. properties of NPs including surface compn., superficial charge, size and shape are considered the key factors that affect the biocompatibility and uptake efficiency of these nanoplatforms. Thanks to the possibility of modifying physico-chem. properties of NPs, it is possible to improve their biocompatibility and uptake efficiency through the functionalization of the NP surface. In this review, we summarize some of the most recent studies in which NP surface modification enhances biocompatibility and uptake. Furthermore, the most used techniques used to assess biocompatibility and uptake are also reported.
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    VanDyke, D.; Kyriacopulos, P.; Yassini, B.; Wright, A.; Burkhart, E.; Jacek, S.; Pratt, M.; Peterson, C. R.; Rai, P. Nanoparticle Based Combination Treatments for Targeting Multiple Hallmarks of Cancer. Int. J. nano Stud. Technol. 2016, 1– 18,  DOI: 10.19070/2167-8685-SI04001
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    Woodward, J.; Kennel, S. J.; Stuckey, A.; Osborne, D.; Wall, J.; Rondinone, A. J.; Standaert, R. F.; Mirzadeh, S. LaPO4 Nanoparticles Doped with Actinium-225 That Partially Sequester Daughter Radionuclides. Bioconjugate Chem. 2011, 22, 766– 776,  DOI: 10.1021/bc100574f
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    LaPO4 Nanoparticles Doped with Actinium-225 that Partially Sequester Daughter Radionuclides
    Woodward, Jonathan; Kennel, Stephen J.; Stuckey, Alan; Osborne, Dustin; Wall, Jonathan; Rondinone, Adam J.; Standaert, Robert F.; Mirzadeh, Saed
    Bioconjugate Chemistry (2011), 22 (4), 766-776CODEN: BCCHES; ISSN:1043-1802. (American Chemical Society)
    Nanoscale materials have been envisioned as carriers for various therapeutic drugs, including radioisotopes. Inorg. nanoparticles (NPs) are particularly appealing vehicles for targeted radiotherapy because they can package several radioactive atoms into a single carrier and can potentially retain daughter radioisotopes produced by in vivo generators such as actinium-225 (225Ac, t1/2 = 10 d). Decay of this radioisotope to stable bismuth-209 proceeds through a chain of short-lived daughters accompanied by the emission of four α-particles that release >27 MeV of energy. The challenge in realizing the enhanced cytotoxic potential of in vivo generators lies in retaining the daughter nuclei at the therapy site. When 225Ac is attached to targeting agents via std. chelate conjugation methods, all of the daughter radionuclides are released after the initial α-decay occurs. In this work, 225Ac was incorporated into lanthanum phosphate NPs to det. whether the radioisotope and its daughters would be retained within the dense mineral lattice. Further, the 225Ac-doped NPs were conjugated to the monoclonal antibody mAb 201B, which targets mouse lung endothelium through the vasculature, to ascertain the targeting efficacy and in vivo retention of radioisotopes. Std. biodistribution techniques and microSPECT/CT imaging of 225Ac as well as the daughter radioisotopes showed that the NPs accumulated rapidly in mouse lung after i.v. injection. By showing that excess, competing, uncoupled antibodies or NPs coupled to control mAbs are deposited primarily in the liver and spleen, specific targeting of NP-mAb 201B conjugates was demonstrated. Biodistribution anal. showed that ∼ 30% of the total injected dose of La(225Ac)PO4 NPs accumulated in mouse lungs 1 h postinjection, yielding a value of % ID/g >200. Furthermore, after 24 h, 80% of the 213Bi daughter produced from 225Ac decay was retained within the target organ and 213Bi retention increased to ∼ 87% at 120 h. In vitro analyses, conducted over a 1 mo interval, demonstrated that ∼ 50% of the daughters were retained within the La(225Ac)PO4 NPs at any point over that time frame. Although most of the γ-rays from radionuclides in the 225Ac decay chain are too energetic to be captured efficiently by SPECT detectors, appropriate energy windows were found that provided dramatic microSPECT images of the NP distribution in vivo. We conclude that La(225Ac)PO4-mAb 201B conjugates can be targeted efficiently to mouse lung while partially retaining daughter products and that targeting can be monitored by biodistribution techniques and microSPECT imaging.
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    Rojas, J. V.; Woodward, J. D.; Chen, N.; Rondinone, A. J.; Castano, C. H.; Mirzadeh, S. Synthesis and Characterization of Lanthanum Phosphate Nanoparticles as Carriers for 223Ra and 225Ra for Targeted Alpha Therapy. Nucl. Med. Biol. 2015, 42, 614– 620,  DOI: 10.1016/j.nucmedbio.2015.03.007
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    McLaughlin, M. F.; Woodward, J.; Boll, R. A.; Rondinone, A. J.; Mirzadeh, S.; Robertson, J. D. Gold-Coated Lanthanide Phosphate Nanoparticles for an 225Ac in Vivo Alpha Generator. Radiochim. Acta 2013, 101, 595– 600,  DOI: 10.1524/ract.2013.2066
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    Gold-coated lanthanide phosphate nanoparticles for an 225Ac in vivo alpha generator
    McLaughlin, M. F.; Woodward, J.; Boll, R. A.; Rondinone, A. J.; Mirzadeh, S.; Robertson, J. D.
    Radiochimica Acta (2013), 101 (9), 595-600CODEN: RAACAP; ISSN:0033-8230. (Oldenbourg Wissenschaftsverlag GmbH)
    Retaining radioactive daughter products at a clin. relevant target site remains one of the major challenges in development of in vivo α generators with radionuclides such as 225Ac and 223Ra. In this work, we examine the ability of layered nanoparticle constructs to retain 225Ac and the first decay daughter, 221Fr. Actinium-225 is cocrystalized in a lanthanide phosphate nanoparticle consisting of varying amts. of La and Gd. Addnl. lanthanide phosphate layers improve retention capability while an outer layer of gold facilitates the attachment of targeting moieties for in vivo use. Retention of 225Ac in the nanoparticles is near quant. while the 221Fr retention varies from 60-89% as a function of time, the no. of layers, and nanoparticle compn. Decay cor. radiochem. yield in the multi-shell syntheses are high (76%) and comparable to or better than existing delivery approaches.
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    Toro-González, M.; Peacock, A.; Miskowiec, A.; Cullen, D. A.; Copping, R.; Mirzadeh, S.; Davern, S. M. Tailoring the Radionuclide Encapsulation and Surface Chemistry of La(223Ra)VO4 Nanoparticles for Targeted Alpha Therapy. J. Nanotheranostics 2021, 2, 33– 50,  DOI: 10.3390/jnt2010003
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    Toro-González, M.; Dame, A. N.; Foster, C. M.; Millet, L. J.; Woodward, J. D.; Rojas, J. V.; Mirzadeh, S.; Davern, S. M. Quantitative Encapsulation and Retention of 227Th and Decay Daughters in Core–Shell Lanthanum Phosphate Nanoparticles. Nanoscale 2020, 12, 9744– 9755,  DOI: 10.1039/D0NR01172J
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    Toro-González, M.; Copping, R.; Mirzadeh, S.; Rojas, J. V. Multifunctional GdVO4:Eu Core–Shell Nanoparticles Containing 225Ac for Targeted Alpha Therapy and Molecular Imaging. J. Mater. Chem. B 2018, 6, 7985– 7997,  DOI: 10.1039/C8TB02173B
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    Kanematsu, N.; Inaniwa, T.; Koba, Y. Relationship between Electron Density and Effective Densities of Body Tissues for Stopping, Scattering, and Nuclear Interactions of Proton and Ion Beams. Med. Phys. 2012, 39, 1016– 1020,  DOI: 10.1118/1.3679339
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    Greaves, G.; Hinks, J. A.; Busby, P.; Mellors, N. J.; Ilinov, A.; Kuronen, A.; Nordlund, K.; Donnelly, S. E. Enhanced Sputtering Yields from Single-Ion Impacts on Gold Nanorods. Phys. Rev. Lett. 2013, 111, 065504  DOI: 10.1103/PhysRevLett.111.065504
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    Holzwarth, U.; Ojea Jimenez, I.; Calzolai, L. A Random Walk Approach to Estimate the Confinement of α-Particle Emitters in Nanoparticles for Targeted Radionuclide Therapy. EJNMMI Radiopharm. Chem. 2018, 3, 9,  DOI: 10.1186/s41181-018-0042-3
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    Thijssen, L.; Schaart, D. R.; De Vries, D.; Morgenstern, A.; Bruchertseifer, F.; Denkova, A. G. Polymersomes as Nano-Carriers to Retain Harmful Recoil Nuclides in Alpha Radionuclide Therapy: A Feasibility Study. Radiochim. Acta 2012, 100, 473– 481,  DOI: 10.1524/ract.2012.1935
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    de Kruijff, R. M.; Drost, K.; Thijssen, L.; Morgenstern, A.; Bruchertseifer, F.; Lathouwers, D.; Wolterbeek, H. T.; Denkova, A. G. Improved 225Ac Daughter Retention in InPO4 Containing Polymersomes. Appl. Radiat. Isot. 2017, 128, 183– 189,  DOI: 10.1016/j.apradiso.2017.07.030
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    Improved 225Ac daughter retention in InPO4 containing polymersomes
    de Kruijff, R. M.; Drost, K.; Thijssen, L.; Morgenstern, A.; Bruchertseifer, F.; Lathouwers, D.; Wolterbeek, H. T.; Denkova, A. G.
    Applied Radiation and Isotopes (2017), 128 (), 183-189CODEN: ARISEF; ISSN:0969-8043. (Elsevier Ltd.)
    Alpha-emitting radionuclides like actinium-225 (225Ac) are ideal candidates for the treatment of small metastasised tumors, where the long half-life of 225Ac enables it to also reach less accessible tumors. The main challenge lies in retaining the recoiled alpha-emitting daughter nuclides, which are decoupled from targeting agents upon emission of an alpha particle and can subsequently cause unwanted toxicity to healthy tissue. Polymersomes, vesicles composed of amphiphilic block copolymers, are capable of transporting (radio)pharmaceuticals to tumors, and are ideal candidates for the retention of these daughter nuclides. In this study, the Geant4 Monte Carlo simulation package was used to simulate ideal vesicle designs. Vesicles contg. an InPO4 nanoparticle in the core were found to have the highest recoil retention, and were subsequently synthesized in the lab. The recoil retention of two of the daughter nuclides, namely francium-221 (221Fr) and bismuth-213 (213Bi) was detd. at different vesicle sizes. Recoil retention was found to have improved significantly, from 37 ± 4% and 22 ± 1% to 57 ± 5% and 40 ± 2% for 221Fr and 213Bi resp. for 100 nm polymersomes, as compared to earlier published results by Wang et al. where 225Ac was encapsulated using a hydrophilic chelate (Wang et al. 2014). To better understand the different parameters influencing daughter retention, simulation data was expanded to include vesicle polydispersity and nanoparticle position within the polymersome. The high retention of the recoiling daughters and the 225Ac itself makes this vesicle design very suitable for future in vivo verification.
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    Gangwar, P.; Pandey, M.; Sivakumar, S.; Pala, R. G. S.; Parthasarathy, G. Increased Loading of Eu3+ Ions in Monazite LaVO4 Nanocrystals via Pressure-Driven Phase Transitions. Cryst. Growth Des. 2013, 13, 2344– 2349,  DOI: 10.1021/cg3018908
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    Increased Loading of Eu3+ Ions in Monazite LaVO4 Nanocrystals via Pressure-Driven Phase Transitions
    Gangwar, Pooja; Pandey, Mohnish; Sivakumar, Sri; Pala, Raj Ganesh S.; Parthasarathy, G.
    Crystal Growth & Design (2013), 13 (6), 2344-2349CODEN: CGDEFU; ISSN:1528-7483. (American Chemical Society)
    The concn. of Eu3+ ion/dopant in the LaVO4 monazite nanocrystal phase cannot be increased by the conventional synthetic procedures. The authors demonstrate a unique 3-step methodol. to increase the doping concn. of Eu3+ in the LaVO4 monazite nanocrystals. In the 1st step, Eu3+ is doped (10%) in the zircon LaVO4 nanocrystal phase, which does not have a limitation in terms of Eu3+ ion loading. In the 2nd step, high pressure (∼5 GPa) is used to transform the zircon crystal phase to the monazite phase. In the 3rd step, the pressure is brought back to the atm. level, wherein the monazite crystal phase is retained in its metastable phase with the 10% Eu3+ ion doping concn. The phase transitions were characterized via elec. resistivity data, XRD, Raman spectroscopy, fluorescence spectroscopy, TEM, and d. functional simulations.
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    Jia, C. N.; Sun, L. D.; Yan, Z. G.; Pang, Y. C.; Lü, S. Z.; Yan, C. H. Monazite and Zircon Type LaVO4:Eu Nanocrystals – Synthesis, Luminescent Properties, and Spectroscopic Identification of the Eu3+ Sites. Eur. J. Inorg. Chem. 2010, 2010, 2626– 2635,  DOI: 10.1002/ejic.201000038
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    Nuñez, N. O.; Zambrano, P.; García-Sevillano, J.; Cantelar, E.; Rivera-Fernández, S.; De La Fuente, J. M.; Ocaña, M. Uniform Poly(Acrylic Acid)-Functionalized Lanthanide-Doped LaVO4 Nanophosphors with High Colloidal Stability and Biocompatibility. Eur. J. Inorg. Chem. 2015, 2015, 4546– 4554,  DOI: 10.1002/ejic.201500265
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    Cheng, X.; Guo, D.; Feng, S.; Yang, K.; Wang, Y.; Ren, Y.; Song, Y. Structure and Stability of Monazite- and Zircon-Type LaVO4 under Hydrostatic Pressure. Opt. Mater. (Amst). 2015, 49, 32– 38,  DOI: 10.1016/j.optmat.2015.08.011
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    Oka, Y.; Yao, T.; Yamamoto, N. Hydrothermal Synthesis of Lanthanum Vanadates: Synthesis and Crystal Structures of Zircon-Type LaVO4 and a New Compound LaV3O9. J. Solid State Chem. 2000, 152, 486– 491,  DOI: 10.1006/jssc.2000.8717
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    Hydrothermal Synthesis of Lanthanum Vanadates: Synthesis and Crystal Structures of Zircon-Type LaVO4 and a New Compound LaV3O9
    Oka, Yoshio; Yao, Takeshi; Yamamoto, Naoichi
    Journal of Solid State Chemistry (2000), 152 (2), 486-491CODEN: JSSCBI; ISSN:0022-4596. (Academic Press)
    In the hydrothermal synthesis of lanthanum vanadates, zircon-type LaVO4 and LaV3O9 were obtained and structurally characterized. The former is a metastable phase, and the latter is a new compd. Single-crystal x-ray diffractometry confirmed the zircon-type structure for LaVO4: space group I41/amd with a 7.4578(7), c 6.5417(9) Å, and Z = 4; R = 0.020 and Rw = 0.025 for 276 reflections with I > 3σ(I). The structure consists of isolated VO4 tetrahedra which surround the La atom to form a LaO8 dodecahedron. LaV3O9 adopts the monoclinic system: space group P21/m with a 4.949(2), b 9.547(3), c 7.411(2) Å, β 100.76(2)°, and Z = 2; R = 0.035 and Rw = 0.042 for 1868 reflections with I > 3σ(I). The structure adopts a chain-type one consisting of a V3O9 chain along [010] which is made up of edge-sharing VO5 trigonal-bipyramid pairs and VO4 tetrahedra. The La atom residues between the V3O9 chains and is coordinated with ten oxygens. The present study demonstrates the applicability of hydrothermal method to the synthesis of new and/or metastable lanthanide vanadates. (c) 2000 Academic Press.
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    Precipitation of rare earth vanadates from aqueous solution
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    Journal of Inorganic and Nuclear Chemistry (1977), 39 (8), 1303-7CODEN: JINCAO; ISSN:0022-1902.
    The chem. of V in soln. was studied over the entire pH range by titrating acidic solns. of VO2+ and La3+ or Y3+ with mixed solns. of base and oxidizing agent to ppt. insol. La and Y vanadates. VO2+ was oxidized early in the titrn. to VO2+ which then condensed in soln. to form the anionic vanadate ppts. Using this method, the problem of the instability range at pH 5.5-7.5 caused by pptn. of hydrous V2O5 was avoided.
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    Xu, Z.; Li, C.; Hou, Z.; Peng, C.; Lin, J. Morphological Control and Luminescence Properties of Lanthanide Orthovanadate LnVO4 (Ln = La to Lu) Nano-/Microcrystals Viahydrothermal Process. CrystEngComm 2011, 13, 474– 482,  DOI: 10.1039/C0CE00161A
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    Lotfi, S.; El Ouardi, M.; Ait Ahsaine, H.; Madigou, V.; BaQais, A.; Assani, A.; Saadi, M.; Arab, M. Low-Temperature Synthesis, Characterization and Photocatalytic Properties of Lanthanum Vanadate LaVO4. Heliyon 2023, 9, e17255  DOI: 10.1016/j.heliyon.2023.e17255
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    Zhong, J.; Zhao, W. Novel Dumbbell-like LaVO4:Eu3+ Nanocrystals and Effect of Ba2+ Codoping on Luminescence Properties of LaVO4:Eu3+ Nanocrystals. J. Sol-Gel Sci. Technol. 2015, 73, 133– 140,  DOI: 10.1007/s10971-014-3504-4
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    Tian, L.; Mho, S. Enhanced Photoluminescence of YVO4:Eu3+ by Codoping the Sr2+, Ba2+ or Pb2+ Ion. J. Lumin. 2007, 122–123, 99– 103,  DOI: 10.1016/j.jlumin.2006.01.108
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    Huignard, A.; Gacoin, T.; Boilot, J. P. Synthesis and Luminescence Properties of Colloidal YVO4:Eu Phosphors. Chem. Mater. 2000, 12, 1090– 1094,  DOI: 10.1021/cm990722t
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    Synthesis and Luminescence Properties of Colloidal YVO4:Eu Phosphors
    Huignard, Arnaud; Gacoin, Thierry; Boilot, Jean-Pierre
    Chemistry of Materials (2000), 12 (4), 1090-1094CODEN: CMATEX; ISSN:0897-4756. (American Chemical Society)
    Concd. colloidal solns. of well-dispersed YVO4:Eu nanoparticles are synthesized by pptn. reactions at room temp. and stabilized by Na hexametaphosphate. x-ray diffraction and electron microscopy characterizations show that the cryst. nanoparticles exhibit an ellipsoidal form with 2 characteristic dimensions of ∼15 and 30 nm. In comparison with the bulk, a lower luminescence efficiency as well as a higher concn. quenching are obsd. These deviations are explained as the variations of some characteristics of the colloidal samples, such as the crystallinity and the surface chem. When these parameters are optimized, the quantum yield of the luminescence reaches 38% for the nanoparticles contg. a Eu concn. of 15%.
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    Deblonde, G. J. P.; Zavarin, M.; Kersting, A. B. The Coordination Properties and Ionic Radius of Actinium: A 120-Year-Old Enigma. Coord. Chem. Rev. 2021, 446, 214130  DOI: 10.1016/j.ccr.2021.214130
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    The coordination properties and ionic radius of actinium: A 120-year-old enigma
    Deblonde, Gauthier J.-P.; Zavarin, Mavrik; Kersting, Annie B.
    Coordination Chemistry Reviews (2021), 446 (), 214130CODEN: CCHRAM; ISSN:0010-8545. (Elsevier B.V.)
    A review. Actinium is an elusive element with untamed properties and represents a peculiar case in the periodic table, as its isotopes are all radioactive, the longest-lived one having only a 22-yr half-life, and the availability of actinium isotopes remains very low (microgram level, at best), hindering research on its compds. Despite being a natural element discovered more than 120 years ago, and despite an increasing interest in using one of its isotopes (225Ac) for highly efficient cancer therapies, the chem. of actinium is still largely unknown relative to other elements. Since Ac is the first element of the actinide series, it is accepted that its ion, Ac3+, is the most voluminous trivalent cation of the periodic table. However, the structural data available on Ac3+ compds. are scarce and have mainly been collected in the 1940-1960's, when actinide chem. was still in its infancy, and have not been put in perspective with the advances in the chem. of other elements, making it difficult to accurately evaluate its actual size and coordination chem. Herein, we review progress made on the chem. of lanthanides and actinides and reevaluate the structural data published on Ac3+ since the era of the Manhattan Project. The data are combined across different spectroscopic and characterization methods and presented in the context of periodic trends. When considering crystallog. data, soln. chem. results, and the nuclear properties of actinium isotopes, it appears that some structural parameters ascribed to the Ac3+ ion may have been overestimated. This review can guide researchers interested in actinide sciences and those who are pursuing the development of actinium-based radiotherapies, from isotope prodn. to clin. trials.
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    Su, J.; Mi, X.; Sun, J.; Yang, L.; Hui, C.; Lu, L.; Bai, Z.; Zhang, X. Tunable Luminescence and Energy Transfer Properties in YVO4:Bi3+, Eu3+ Phosphors. J. Mater. Sci. 2017, 52, 782– 792,  DOI: 10.1007/s10853-016-0375-9
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    Tunable luminescence and energy transfer properties in YVO4:Bi3+, Eu3+ phosphors
    Su, Jiangang; Mi, Xiaoyun; Sun, Jiacheng; Yang, Lixin; Hui, Chunlong; Lu, Liping; Bai, Zhaohui; Zhang, Xiyan
    Journal of Materials Science (2017), 52 (2), 782-792CODEN: JMTSAS; ISSN:0022-2461. (Springer)
    In this paper, YVO4:Bi3+, Eu3+ phosphors have been synthesized by high-temp. solid-state method. The samples were characterized by X-ray powder diffraction, photoluminescence spectra, luminescence lifetime, and GSAS structure refinement. The excitation spectrum of YVO4:Bi3+, Eu3+ monitoring at 622 nm was a broad band with major peak located at 280 nm. It contained the charge transfer from 2p orbit of O2- to 4f orbit of Eu3+ (257 nm) and the absorbing from energy level transition of Bi3+ (1S0→3P1, 346 nm) and VO43- (lA1→1T2, 286 nm and lA1→1T1, 320 nm) through gauss fitting. Upon excitation at a wavelength of 280 nm, the major emission peak of YVO4:Bi3+, Eu3+ located at 622 nm (red) was attributed to the elec. dipole transition 5D0→7F2 of Eu3+. The energy transfer mechanism of Bi3+→Eu3+ was also studied to be dipole-quadrupole mechanism of elec. multipole interaction, and the crit. distance between Eu3+ and Bi3+ was calcd. by concn. quenching method. The emission color of YVO4:Bi3+, Eu3+ can be tuned by the energy transfer of ions and the concn. of activator. In a word, the material has a good application prospects in the field of light-emitting diode under UV excitation.
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    Rapp, M.; Lozano, Y.; Fernández-Ramos, M.; Isasi, J.; Palafox, M. A. Superparamagnetic and Light-Emitting Bifunctional Nanocomposites of Iron Oxide and Erbium or Thulium Doped Yttrium Orthovanadate. J. Alloys Compd. 2022, 929, 167065  DOI: 10.1016/j.jallcom.2022.167065
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    Ling-Hu, P.; Guo, X.; Hu, J.; Deng, C.; Cui, R. Anomalous 5D0→7F4 Transition of Eu3+-Doped BaLaGaO4 Phosphors for WLEDs and Plant Growth Applications. Adv. Opt. Mater. 2024, 12, 2301760  DOI: 10.1002/adom.202301760
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    Chi, F.; Wei, X.; Zhou, S.; Chen, Y.; Duan, C.; Yin, M. Enhanced 5D0 → 7F4 Transition and Optical Thermometry of Garnet Type Ca3Ga2Ge3O12:Eu3+ Phosphors. Inorg. Chem. Front. 2018, 5, 1288– 1293,  DOI: 10.1039/C8QI00199E
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    Enhanced 5D0 → 7F4 transition and optical thermometry of garnet type Ca3Ga2Ge3O12:Eu3+ phosphors
    Chi, Fengfeng; Wei, Xiantao; Zhou, Shaoshuai; Chen, Yonghu; Duan, Changkui; Yin, Min
    Inorganic Chemistry Frontiers (2018), 5 (6), 1288-1293CODEN: ICFNAW; ISSN:2052-1553. (Royal Society of Chemistry)
    The garnet type phosphors of Eu3+ doped Ca3Ga2Ge3O12 were synthesized via conventional solid state reaction techniques. The phase purity and luminescence properties of the fabricated phosphors were characterized by X-ray powder diffraction, photoluminescence excitation and emission spectra, temp. dependent emission spectra as well as luminescence decay curves. The phosphors show enhanced red emission from a 5D0 → 7F4 transition of Eu3+ under the excitation of 394 nm. The unusual 5D0 → 7F4 intensity was explained by structural anal. The emission intensity of the phosphors increases with the concn. of Eu3+ until the quenching concn. of 10 mol%. Excited by a pulsed laser of wavelength 610.8 nm, the emission intensity of the 5D0 → 7F4 transition increases monotonously as the temp. increases in the range of 160-360 K. The temp. dependent fluorescence behavior was investigated. The relative sensitivity reaches the max. value of 3.66% K-1 at 160 K and reaches 1.04% K-1 at 300 K. The results show that the garnet type Ca3Ga2Ge3O12:Eu3+ phosphor is a promising material for the application of optical thermometry.
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    Muckley, E. S.; Aytug, T.; Mayes, R.; Lupini, A. R.; Carrillo, J. M. Y.; Goswami, M.; Sumpter, B. G.; Ivanov, I. N. Hierarchical TiO2:Cu2O Nanostructures for Gas/Vapor Sensing and CO2 Sequestration. ACS Appl. Mater. Interfaces 2019, 11, 48466– 48475,  DOI: 10.1021/acsami.9b18824
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    Hierarchical TiO2:Cu2O Nanostructures for Gas/Vapor Sensing and CO2 Sequestration
    Muckley, Eric S.; Aytug, Tolga; Mayes, Richard; Lupini, Andrew R.; Carrillo, Jan-Michael Y.; Goswami, Monojoy; Sumpter, Bobby G.; Ivanov, Ilia N.
    ACS Applied Materials & Interfaces (2019), 11 (51), 48466-48475CODEN: AAMICK; ISSN:1944-8244. (American Chemical Society)
    We investigate the effect of high-surface-area self-assembled TiO2:Cu2O nanostructures for CO2 and relative humidity (RH) gravimetric detection using polyethylenimine (PEI), 1-ethyl-3-methylimidazolium (EMIM), and polyacrylamide (PAAm). Introduction of hierarchical TiO2:Cu2O nanostructures on the surface of quartz crystal microbalance (QCM) sensors is found to significantly improve sensitivity to CO2 and to H2O vapor. The response of EMIM to CO2 increases 5-fold for 100 nm thick TiO2:Cu2O as compared to gold. At ambient CO2 concns. the hierarchical assembly operates as a sensor with excellent reversibility, while at higher pressures the CO2 desorption rate decreases, suggesting possible application for CO2 sequestration under those conditions. The gravimetric response of PEI to CO2 increases by a factor of 3 upon introduction of a 50 nm TiO2:Cu2O layer. The PAAm gravimetric response to water vapor also increases by a factor of 3 and displays improved reversibility with the addn. of 50 nm TiO2:Cu2O structures. We found that TiO2:Cu2O can be used to lower the detection limits for CO22 sensing with EMIM and PEI and lower detection limits for H2O sensing with RAAm by over a factor of two. Coarse-grained and all-atom mol. dynamics simulations indicate the dissociative character of ionic liq. assembly on TiO2:Cu2O interfaces and different distributions of CO2 and H2O mols. on bare and ionic liq.-coated surfaces, confirming exptl. observations. Overall, our results show high potential of hierarchical assemblies of TiO2:Cu2O / room temp. ionic liq. and polymer films for sensors and CO2 sequestration.
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    White, F. D.; Thiele, N. A.; Simms, M. E.; Cary, S. K. Structure and Bonding of a Radium Coordination Compound in the Solid State. Nat. Chem. 2024, 16, 168– 172,  DOI: 10.1038/s41557-023-01366-z
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    Akamo, D. O.; Kumar, N.; Li, Y.; Pekol, C.; Li, K.; Goswami, M.; Hirschey, J.; LaClair, T. J.; Keffer, D. J.; Rios, O.; Gluesenkamp, K. R. Stabilization of Low-Cost Phase Change Materials for Thermal Energy Storage Applications. iScience 2023, 26, 107175  DOI: 10.1016/j.isci.2023.107175
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    Vives, S.; Ramel, D.; Meunier, C. Evolution of the Structure with the Composition and the Defect Arrangement in the Gadolinium and Samarium Doped and Co-Doped Ceria Systems: A Molecular Dynamics Study. Solid State Ionics 2021, 364, 115611  DOI: 10.1016/j.ssi.2021.115611
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    Metal Ion Modeling Using Classical Mechanics
    Li, Pengfei; Merz, Kenneth M., Jr.
    Chemical Reviews (Washington, DC, United States) (2017), 117 (3), 1564-1686CODEN: CHREAY; ISSN:0009-2665. (American Chemical Society)
    A review. Metal ions play significant roles in numerous fields including chem., geochem., biochem. and materials science. With computational tools increasingly becoming important in chem. research, methods have emerged to effectively face the challenge of modeling metal ions in the gas, aq. and solid phases. Herein we review both quantum and classical modeling strategies for metal ion contg. systems that have been developed over the past few decades. This review focuses on classical metal ion modeling based on unpolarized models (including the nonbonded, bonded, cationic dummy atom, and combined models), polarizable models (e.g., the fluctuating charge, Drude oscillator, and the induced dipole models), the angular overlap model, and valence bond based models. Quantum mech. studies of metal ion contg. systems at the semiempirical, ab initio and d. functional levels of theory are reviewed as well with a particular focus on how these methods inform classical modeling efforts. Finally, conclusions and future prospects and directions are offered that will further enhance the classical modeling of metal ion contg. systems.
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    Boll, R. A.; Malkemus, D.; Mirzadeh, S. Production of Actinium-225 for Alpha Particle Mediated Radioimmunotherapy. Appl. Radiat. Isot. 2005, 62, 667– 679,  DOI: 10.1016/j.apradiso.2004.12.003
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    Production of actinium-225 for alpha particle mediated radioimmunotherapy
    Boll, Rose A.; Malkemus, Dairin; Mirzadeh, Saed
    Applied Radiation and Isotopes (2005), 62 (5), 667-679CODEN: ARISEF; ISSN:0969-8043. (Elsevier B.V.)
    The initial clin. trials for treatment of acute myeloid leukemia demonstrated the effectiveness of the alpha emitter 213Bi in killing cancer cells. Bi-213 is obtained from a radionuclide generator system from decay of 10-days 225Ac parent. Recent pre-clin. studies also showed the potential application of both 213Bi, and the 225Ac parent radionuclide in a variety of cancer systems and targeted radiotherapy. This paper describes the 5 years of experience in prodn. of 225Ac in partial support of the on-going clin. trials. A 4-step chem. process, consisting of both anion and cation exchange chromatog., is used for routine sepn. of carrier-free 225Ac from a mixt. of 228Th, 229Th and 232Th. The sepn. of Ra and Ac from Th is achieved using the macroporous anion exchange resin MP1 in 8 M HNO3 media. Two sequential MP1/NO3 columns provide a sepn. factor of ∼106 for Ra and Ac from Th. The sepn. of Ac from Ra is accomplished on a low crosslinking cation exchange resin AG50-X4 using 1.2M HNO3 as eluant. Two sequential AG50/NO3 columns provide a sepn. factor of ∼102 for Ac from Ra. A 60-day processing schedule was adopted to reduce the processing cost and to provide the highest levels of 225Ac possible. Over an 8-wk campaign, a total of ∼100 mCi of 225Ac (∼80% of the theor. yield) is shipped in 5-6 batches, with the 1st batch typically consisting of ∼50 mCi. After the initial sepn. and purifn. of Ac, the Ra pool is re-processed on a bi-weekly schedule or as needed to provide smaller batches of 225Ac. The averaged radioisotopic purity of the 225Ac was 99.6 ± 0.7% with a 225Ra content of ≤0.6%, and an av. 229Th content of (4+5-4)×10-5%.
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    Huignard, A.; Buissette, V.; Laurent, G.; Gacoin, T.; Boilot, J. P. Synthesis and Characterizations of YVO4: Eu Colloids. Chem. Mater. 2002, 14, 2264– 2269,  DOI: 10.1021/cm011263a
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    Synthesis and Characterizations of YVO4:Eu Colloids
    Huignard, A.; Buissette, V.; Laurent, G.; Gacoin, T.; Boilot, J. P.
    Chemistry of Materials (2002), 14 (5), 2264-2269CODEN: CMATEX; ISSN:0897-4756. (American Chemical Society)
    A new process for the synthesis of colloidal Eu-doped YVO4 with a particle diam. of ∼10 nm is presented. Nanocrystals are produced by pptn. of citrate complexes of rare earth salts with Na3VO4. NMR and IR studies show that the interaction between citrate ligands and lanthanide ions limits the growth of particles and ensures the stability of the colloidal solns. through electrostatic and steric repulsions. The optimized process leads to stable and highly concd. transparent colloidal solns. in H2O (≤400 g/L).
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    Toby, B. H.; Von Dreele, R. B. GSAS-II: The Genesis of a Modern Open-Source All Purpose Crystallography Software Package. J. Appl. Crystallogr. 2013, 46, 544– 549,  DOI: 10.1107/S0021889813003531
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    GSAS-II: the genesis of a modern open-source all purpose crystallography software package
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    Journal of Applied Crystallography (2013), 46 (2), 544-549CODEN: JACGAR; ISSN:0021-8898. (International Union of Crystallography)
    The newly developed GSAS-II software is a general purpose package for data redn., structure soln. and structure refinement that can be used with both single-crystal and powder diffraction data from both neutron and x-ray sources, including lab. and synchrotron sources, collected on both two- and 1-dimensional detectors. It is intended that GSAS-II will eventually replace both the GSAS and the EXPGUI packages, as well as many other utilities. GSAS-II is open source and is written largely in object-oriented Python but offers speeds comparable to compiled code because of its reliance on the Python NumPy and SciPy packages for computation. It runs on all common computer platforms and offers highly integrated graphics, both for a user interface and for interpretation of parameters. The package can be applied to all stages of crystallog. anal. for const.-wavelength x-ray and neutron data. Plans for considerable addnl. development are discussed.
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  • Abstract

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    Figure 1

    Figure 1. (a, d) Diffraction patterns, (b, e) Raman spectra, and (e, f) size distribution of (a–c) La(1–x)EuxVO4 and (d–f) (La0.9Eu0.1)(1–y)BayVO4 of nanoconstructs.

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    Figure 2

    Figure 2. Excitation spectra, emission spectra, and emission peak ratio of (a–c) La(1–x)EuxVO4 and (d–f) (La0.9Eu0.1)(1–y)BayVO4 nanoconstructs.

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    Figure 3

    Figure 3. (a, b) Emission spectra of La0.9Eu0.1VO4, La0.9Eu0.1[225Ac]AcVO4, and decayed La0.9Eu0.1[225Ac]AcVO4 nanoconstructs. The emission spectra were normalized to the 618 nm peak corresponding to the Eu3+5D0 → 7F2 transition. (c) Emission spectra of La[225Ac]AcVO4 and decayed La[225Ac]VO4 nanoconstructs. The emission spectra were normalized to the 450 nm peak corresponding to the [VO4]3–3T1 → 1A1 and 3T2 → lA1 energy transfer. (d) Encapsulation efficiency of [223Ra]Ra2+ within (La0.9Eu0.1)(1–y)BayVO4 nanoconstructs.

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    Figure 4

    Figure 4. Structural details of Ac–Ln and Ra–Ln nanoconstructs at 3 mol % of Ac/Ra doping at 67 °C. Three different RDFs, Ac/Ra–O, La–O, and Eu–O are shown for the (a) Ac–Ln system and (b) Ra–Ln system. The comparison between Ac–O and Ra–O are shown in (c). Colors are represented in the legends. (d, e) Simulation snapshots of Ac–O and Ra–O systems, respectively. Water molecules are not shown for clarity. (f, g) Closeup of the nanoconstructs for Ac–O and Ra–O systems, respectively. Color scheme in the snapshots: Ac/Ra─blue, La─cyan, Eu─yellow, V─green, and O─red. The low-temperature, T = 27 °C, RDFs are compared in Figure S2 showing structural stability of the nanoconstructs.

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    Figure 5

    Figure 5. Structures of 25 mol % Ba/Ra doped lanthanide nanoconstructs. (a, b) Simulation snapshots of Ba- and Ra-doped nanoconstructs. (c, d) Closeup of Ba- and Ra-doped nanoclusters. Color scheme of the snapshots: Ba/Ra─blue, La─yellow, Eu─purple, V─green, and O─red. Water molecules are not shown for clarity. (e, f) RDF of metallic cations with the oxygen of vanadates for Ba- and Ra-doped nanoconstructs. (g) Comparison of RDFs between Ba- and Ra-doped nanoconstructs.

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    Figure 6

    Figure 6. Mean-square-displacement (MSD) of La, Eu, and Ac/Ra of Ac-doped Ln (a,c) and Ra-doped Ln (b,d) compared with La and Eu atoms of the lanthanides. Low- and high-temperature MSDs are shown in (a), (b) at T = 27 °C, and (c), (d) at T = 67 °C respectively. A comparison of Eu (red and magenta), Ac (black), and Ra (blue) MSDs for Ac–Ln and Ra–Ln systems is shown in (e). Comparison with respect to temperature for these two systems is shown in (f); the solid lines are for T = 27 °C, and dashed lines are for T = 67 °C. MSD is lower at higher temperatures.

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    Figure 7

    Figure 7. Lanthanide vanadate simulations in an aqueous environment. (a) Initial system setup containing La, Eu, and VO4 ions in g/cm3 water randomly distributed in a box of 40 nm3. (b) 3D structure of the Ln nanoconstruct at experimental temperature, 67 °C. Water molecules are not shown for clarity. (c) Top view (2D) snapshot of the lanthanide nanoconstruct as can be observed from the TEM of experimentally prepared nanoconstructs. The background dots are neutral La atoms that stay mostly in water in a solvated state. (d) TEM nanoconstruct of lanthanide vanadate showing a similar structure to that derived in (c).

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      9
      Overview of the most promising radionuclides for targeted alpha therapy: the "hopeful eight"
      Eychenne, Romain; Cherel, Michel; Haddad, Ferid; Guerard, Francois; Gestin, Jean-Francois
      Pharmaceutics (2021), 13 (6), 906CODEN: PHARK5; ISSN:1999-4923. (MDPI AG)
      Among all existing radionuclides, only a few are of interest for therapeutic applications and more specifically for targeted alpha therapy (TAT). From this selection, actinium-225, astatine-211, bismuth-212, bismuth-213, lead-212, radium-223, terbium-149 and thorium-227 are considered as the most suitable. Despite common general features, they all have their own phys. characteristics that make them singular and so promising for TAT. These radionuclides were largely studied over the last two decades, leading to a better knowledge of their prodn. process and chem. behavior, allowing for an increasing no. of biol. evaluations. The aim of this review is to summarize the main properties of these eight chosen radionuclides. An overview from their availability to the resulting clin. studies, by way of chem. design and preclin. studies is discussed.
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    10. 10
      de Kruijff, R. M.; Wolterbeek, H. T.; Denkova, A. G. A Critical Review of Alpha Radionuclide Therapy─How to Deal with Recoiling Daughters?. Pharmaceuticals 2015, 8, 321– 336,  DOI: 10.3390/ph8020321
      10
      A critical review of alpha radionuclide therapy-how to deal with recoiling daughters?
      de Kruijff, Robin M.; Wolterbeek, Hubert T.; Denkova, Antonia G.
      Pharmaceuticals (2015), 8 (2), 321-336CODEN: PHARH2; ISSN:1424-8247. (MDPI AG)
      This review presents an overview of the successes and challenges currently faced in alpha radionuclide therapy. Alpha particles have an advantage in killing tumor cells as compared to beta or gamma radiation due to their short penetration depth and high linear energy transfer (LET). Touching briefly on the clin. successes of radionuclides emitting only one alpha particle, the main focus of this article lies on those alpha-emitting radionuclides with multiple alpha-emitting daughters in their decay chain. While having the advantage of longer half-lives, the recoiled daughters of radionuclides like 224Ra (radium), 223Ra, and 225Ac (actinium) can do significant damage to healthy tissue when not retained at the tumor site. Three different approaches to deal with this problem are discussed: encapsulation in a nano-carrier, fast uptake of the alpha emitting radionuclides in tumor cells, and local administration. Each approach has been shown to have its advantages and disadvantages, but when larger activities need to be used clin., nano-carriers appear to be the most promising soln. for reducing toxic effects, provided there is no accumulation in healthy tissue.
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    11. 11
      Merkx, R. I. J.; Rijpkema, M.; Franssen, G. M.; Kip, A.; Smeets, B.; Morgenstern, A.; Bruchertseifer, F.; Yan, E.; Wheatcroft, M. P.; Oosterwijk, E.; Mulders, P. F. A.; Heskamp, S. Carbonic Anhydrase IX-Targeted α-Radionuclide Therapy with 225Ac Inhibits Tumor Growth in a Renal Cell Carcinoma Model. Pharmaceuticals 2022, 15, 570,  DOI: 10.3390/ph15050570
      There is no corresponding record for this reference.
    12. 12
      Membreno, R.; Cook, B. E.; Zeglis, B. M. Pretargeted Radioimmunotherapy Based on the Inverse Electron Demand Diels-Alder Reaction. J. Vis. Exp. 2019, 2019, 59041  DOI: 10.3791/59041
      There is no corresponding record for this reference.
    13. 13
      Toro-González, M.; Dame, A. N.; Mirzadeh, S.; Rojas, J. V. Gadolinium Vanadate Nanocrystals as Carriers of α-Emitters (225Ac, 227Th) and Contrast Agents. J. Appl. Phys. 2019, 125, 214901  DOI: 10.1063/1.5096880
      13
      Gadolinium vanadate nanocrystals as carriers of α-emitters (225Ac, 227Th) and contrast agents
      Toro-Gonzalez, Miguel; Dame, Ashley N.; Mirzadeh, Saed; Rojas, Jessika V.
      Journal of Applied Physics (Melville, NY, United States) (2019), 125 (21), 214901/1-214901/11CODEN: JAPIAU; ISSN:0021-8979. (American Institute of Physics)
      Gadolinium vanadate (GdVO4) core and core + 2 shell nanocrystals (NCs) were evaluated for in vitro retention of 225Ac, 227Th, and their first decay daughters, 221Fr and 223Ra, resp. GdVO4 NCs with a tetragonal crystal system (zircon-type) and spherical morphol. were obtained by pptn. of GdCl3 and Na3VO4 using sodium citrate as a complexing agent. The growth of two nonradioactive GdVO4 shells on both Gd(225Ac)VO4 and Gd(227Th)VO4 core NCs was demonstrated by an increase of 0.7 nm and 2 nm in the crystallite size, resp. The max. leakage of 225Ac was 15% and 2.4% from core and core + 2 shells, whereas the leakage of 227Th was 3% and 1.5%, resp. The presence of two nonradioactive GdVO4 shells increased the retention of 221Fr and 223Ra by 20% and 15% with respect to core NCs. Furthermore, a longitudinal proton relaxivity, r1 = 0.9289 s-1 mM-1, confirmed their potential application as contrast agents for magnetic resonance imaging. In summary, GdVO4 NCs show promising capabilities as radionuclide carriers with partial retention of decay daughters and as contrast agents for theranostic applications. (c) 2019 American Institute of Physics.
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    14. 14
      Toro-González, M.; Dame, A. N.; Mirzadeh, S.; Rojas, J. V. Encapsulation and Retention of 225Ac, 223Ra, 227Th, and Decay Daughters in Zircon-Type Gadolinium Vanadate Nanoparticles. Radiochim. Acta 2020, 108, 967– 977,  DOI: 10.1515/ract-2019-3206
      There is no corresponding record for this reference.
    15. 15
      Tao, Y.; Sun, Y.; Shi, K.; Pei, P.; Ge, F.; Yang, K.; Liu, T. Versatile Labeling of Multiple Radionuclides onto a Nanoscale Metal–Organic Framework for Tumor Imaging and Radioisotope Therapy. Biomater. Sci. 2021, 9, 2947– 2954,  DOI: 10.1039/D0BM02225J
      There is no corresponding record for this reference.
    16. 16
      Tanahashi, K.; Mikos, A. G. Effect of Hydrophilicity and Agmatine Modification on Degradation of Poly(Propylene Fumarate-Co-Ethylene Glycol) Hydrogels. J. Biomed. Mater. Res. Part A 2003, 67A, 1148– 1154,  DOI: 10.1002/jbm.a.10147
      There is no corresponding record for this reference.
    17. 17
      Sanità, G.; Carrese, B.; Lamberti, A. Nanoparticle Surface Functionalization: How to Improve Biocompatibility and Cellular Internalization. Front. Mol. Biosci. 2020, 7, 587012  DOI: 10.3389/fmolb.2020.587012
      17
      Nanoparticle surface functionalization: how to improve biocompatibility and cellular internalization
      Sanita, Gennaro; Carrese, Barbara; Lamberti, Annalisa
      Frontiers in Molecular Biosciences (2020), 7 (), 587012CODEN: FMBRBS; ISSN:2296-889X. (Frontiers Media S.A.)
      A review. The use of nanoparticles (NP) in diagnosis and treatment of many human diseases, including cancer, is of increasing interest. However, cytotoxic effects of NPs on cells and the uptake efficiency significantly limit their use in clin. practice. The physico-chem. properties of NPs including surface compn., superficial charge, size and shape are considered the key factors that affect the biocompatibility and uptake efficiency of these nanoplatforms. Thanks to the possibility of modifying physico-chem. properties of NPs, it is possible to improve their biocompatibility and uptake efficiency through the functionalization of the NP surface. In this review, we summarize some of the most recent studies in which NP surface modification enhances biocompatibility and uptake. Furthermore, the most used techniques used to assess biocompatibility and uptake are also reported.
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    18. 18
      VanDyke, D.; Kyriacopulos, P.; Yassini, B.; Wright, A.; Burkhart, E.; Jacek, S.; Pratt, M.; Peterson, C. R.; Rai, P. Nanoparticle Based Combination Treatments for Targeting Multiple Hallmarks of Cancer. Int. J. nano Stud. Technol. 2016, 1– 18,  DOI: 10.19070/2167-8685-SI04001
      There is no corresponding record for this reference.
    19. 19
      Woodward, J.; Kennel, S. J.; Stuckey, A.; Osborne, D.; Wall, J.; Rondinone, A. J.; Standaert, R. F.; Mirzadeh, S. LaPO4 Nanoparticles Doped with Actinium-225 That Partially Sequester Daughter Radionuclides. Bioconjugate Chem. 2011, 22, 766– 776,  DOI: 10.1021/bc100574f
      19
      LaPO4 Nanoparticles Doped with Actinium-225 that Partially Sequester Daughter Radionuclides
      Woodward, Jonathan; Kennel, Stephen J.; Stuckey, Alan; Osborne, Dustin; Wall, Jonathan; Rondinone, Adam J.; Standaert, Robert F.; Mirzadeh, Saed
      Bioconjugate Chemistry (2011), 22 (4), 766-776CODEN: BCCHES; ISSN:1043-1802. (American Chemical Society)
      Nanoscale materials have been envisioned as carriers for various therapeutic drugs, including radioisotopes. Inorg. nanoparticles (NPs) are particularly appealing vehicles for targeted radiotherapy because they can package several radioactive atoms into a single carrier and can potentially retain daughter radioisotopes produced by in vivo generators such as actinium-225 (225Ac, t1/2 = 10 d). Decay of this radioisotope to stable bismuth-209 proceeds through a chain of short-lived daughters accompanied by the emission of four α-particles that release >27 MeV of energy. The challenge in realizing the enhanced cytotoxic potential of in vivo generators lies in retaining the daughter nuclei at the therapy site. When 225Ac is attached to targeting agents via std. chelate conjugation methods, all of the daughter radionuclides are released after the initial α-decay occurs. In this work, 225Ac was incorporated into lanthanum phosphate NPs to det. whether the radioisotope and its daughters would be retained within the dense mineral lattice. Further, the 225Ac-doped NPs were conjugated to the monoclonal antibody mAb 201B, which targets mouse lung endothelium through the vasculature, to ascertain the targeting efficacy and in vivo retention of radioisotopes. Std. biodistribution techniques and microSPECT/CT imaging of 225Ac as well as the daughter radioisotopes showed that the NPs accumulated rapidly in mouse lung after i.v. injection. By showing that excess, competing, uncoupled antibodies or NPs coupled to control mAbs are deposited primarily in the liver and spleen, specific targeting of NP-mAb 201B conjugates was demonstrated. Biodistribution anal. showed that ∼ 30% of the total injected dose of La(225Ac)PO4 NPs accumulated in mouse lungs 1 h postinjection, yielding a value of % ID/g >200. Furthermore, after 24 h, 80% of the 213Bi daughter produced from 225Ac decay was retained within the target organ and 213Bi retention increased to ∼ 87% at 120 h. In vitro analyses, conducted over a 1 mo interval, demonstrated that ∼ 50% of the daughters were retained within the La(225Ac)PO4 NPs at any point over that time frame. Although most of the γ-rays from radionuclides in the 225Ac decay chain are too energetic to be captured efficiently by SPECT detectors, appropriate energy windows were found that provided dramatic microSPECT images of the NP distribution in vivo. We conclude that La(225Ac)PO4-mAb 201B conjugates can be targeted efficiently to mouse lung while partially retaining daughter products and that targeting can be monitored by biodistribution techniques and microSPECT imaging.
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    20. 20
      Rojas, J. V.; Woodward, J. D.; Chen, N.; Rondinone, A. J.; Castano, C. H.; Mirzadeh, S. Synthesis and Characterization of Lanthanum Phosphate Nanoparticles as Carriers for 223Ra and 225Ra for Targeted Alpha Therapy. Nucl. Med. Biol. 2015, 42, 614– 620,  DOI: 10.1016/j.nucmedbio.2015.03.007
      There is no corresponding record for this reference.
    21. 21
      McLaughlin, M. F.; Woodward, J.; Boll, R. A.; Rondinone, A. J.; Mirzadeh, S.; Robertson, J. D. Gold-Coated Lanthanide Phosphate Nanoparticles for an 225Ac in Vivo Alpha Generator. Radiochim. Acta 2013, 101, 595– 600,  DOI: 10.1524/ract.2013.2066
      21
      Gold-coated lanthanide phosphate nanoparticles for an 225Ac in vivo alpha generator
      McLaughlin, M. F.; Woodward, J.; Boll, R. A.; Rondinone, A. J.; Mirzadeh, S.; Robertson, J. D.
      Radiochimica Acta (2013), 101 (9), 595-600CODEN: RAACAP; ISSN:0033-8230. (Oldenbourg Wissenschaftsverlag GmbH)
      Retaining radioactive daughter products at a clin. relevant target site remains one of the major challenges in development of in vivo α generators with radionuclides such as 225Ac and 223Ra. In this work, we examine the ability of layered nanoparticle constructs to retain 225Ac and the first decay daughter, 221Fr. Actinium-225 is cocrystalized in a lanthanide phosphate nanoparticle consisting of varying amts. of La and Gd. Addnl. lanthanide phosphate layers improve retention capability while an outer layer of gold facilitates the attachment of targeting moieties for in vivo use. Retention of 225Ac in the nanoparticles is near quant. while the 221Fr retention varies from 60-89% as a function of time, the no. of layers, and nanoparticle compn. Decay cor. radiochem. yield in the multi-shell syntheses are high (76%) and comparable to or better than existing delivery approaches.
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    22. 22
      Toro-González, M.; Peacock, A.; Miskowiec, A.; Cullen, D. A.; Copping, R.; Mirzadeh, S.; Davern, S. M. Tailoring the Radionuclide Encapsulation and Surface Chemistry of La(223Ra)VO4 Nanoparticles for Targeted Alpha Therapy. J. Nanotheranostics 2021, 2, 33– 50,  DOI: 10.3390/jnt2010003
      There is no corresponding record for this reference.
    23. 23
      Toro-González, M.; Dame, A. N.; Foster, C. M.; Millet, L. J.; Woodward, J. D.; Rojas, J. V.; Mirzadeh, S.; Davern, S. M. Quantitative Encapsulation and Retention of 227Th and Decay Daughters in Core–Shell Lanthanum Phosphate Nanoparticles. Nanoscale 2020, 12, 9744– 9755,  DOI: 10.1039/D0NR01172J
      There is no corresponding record for this reference.
    24. 24
      Toro-González, M.; Copping, R.; Mirzadeh, S.; Rojas, J. V. Multifunctional GdVO4:Eu Core–Shell Nanoparticles Containing 225Ac for Targeted Alpha Therapy and Molecular Imaging. J. Mater. Chem. B 2018, 6, 7985– 7997,  DOI: 10.1039/C8TB02173B
      There is no corresponding record for this reference.
    25. 25
      Kanematsu, N.; Inaniwa, T.; Koba, Y. Relationship between Electron Density and Effective Densities of Body Tissues for Stopping, Scattering, and Nuclear Interactions of Proton and Ion Beams. Med. Phys. 2012, 39, 1016– 1020,  DOI: 10.1118/1.3679339
      There is no corresponding record for this reference.
    26. 26
      Greaves, G.; Hinks, J. A.; Busby, P.; Mellors, N. J.; Ilinov, A.; Kuronen, A.; Nordlund, K.; Donnelly, S. E. Enhanced Sputtering Yields from Single-Ion Impacts on Gold Nanorods. Phys. Rev. Lett. 2013, 111, 065504  DOI: 10.1103/PhysRevLett.111.065504
      There is no corresponding record for this reference.
    27. 27
      Holzwarth, U.; Ojea Jimenez, I.; Calzolai, L. A Random Walk Approach to Estimate the Confinement of α-Particle Emitters in Nanoparticles for Targeted Radionuclide Therapy. EJNMMI Radiopharm. Chem. 2018, 3, 9,  DOI: 10.1186/s41181-018-0042-3
      There is no corresponding record for this reference.
    28. 28
      Thijssen, L.; Schaart, D. R.; De Vries, D.; Morgenstern, A.; Bruchertseifer, F.; Denkova, A. G. Polymersomes as Nano-Carriers to Retain Harmful Recoil Nuclides in Alpha Radionuclide Therapy: A Feasibility Study. Radiochim. Acta 2012, 100, 473– 481,  DOI: 10.1524/ract.2012.1935
      There is no corresponding record for this reference.
    29. 29
      de Kruijff, R. M.; Drost, K.; Thijssen, L.; Morgenstern, A.; Bruchertseifer, F.; Lathouwers, D.; Wolterbeek, H. T.; Denkova, A. G. Improved 225Ac Daughter Retention in InPO4 Containing Polymersomes. Appl. Radiat. Isot. 2017, 128, 183– 189,  DOI: 10.1016/j.apradiso.2017.07.030
      29
      Improved 225Ac daughter retention in InPO4 containing polymersomes
      de Kruijff, R. M.; Drost, K.; Thijssen, L.; Morgenstern, A.; Bruchertseifer, F.; Lathouwers, D.; Wolterbeek, H. T.; Denkova, A. G.
      Applied Radiation and Isotopes (2017), 128 (), 183-189CODEN: ARISEF; ISSN:0969-8043. (Elsevier Ltd.)
      Alpha-emitting radionuclides like actinium-225 (225Ac) are ideal candidates for the treatment of small metastasised tumors, where the long half-life of 225Ac enables it to also reach less accessible tumors. The main challenge lies in retaining the recoiled alpha-emitting daughter nuclides, which are decoupled from targeting agents upon emission of an alpha particle and can subsequently cause unwanted toxicity to healthy tissue. Polymersomes, vesicles composed of amphiphilic block copolymers, are capable of transporting (radio)pharmaceuticals to tumors, and are ideal candidates for the retention of these daughter nuclides. In this study, the Geant4 Monte Carlo simulation package was used to simulate ideal vesicle designs. Vesicles contg. an InPO4 nanoparticle in the core were found to have the highest recoil retention, and were subsequently synthesized in the lab. The recoil retention of two of the daughter nuclides, namely francium-221 (221Fr) and bismuth-213 (213Bi) was detd. at different vesicle sizes. Recoil retention was found to have improved significantly, from 37 ± 4% and 22 ± 1% to 57 ± 5% and 40 ± 2% for 221Fr and 213Bi resp. for 100 nm polymersomes, as compared to earlier published results by Wang et al. where 225Ac was encapsulated using a hydrophilic chelate (Wang et al. 2014). To better understand the different parameters influencing daughter retention, simulation data was expanded to include vesicle polydispersity and nanoparticle position within the polymersome. The high retention of the recoiling daughters and the 225Ac itself makes this vesicle design very suitable for future in vivo verification.
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    30. 30
      Gangwar, P.; Pandey, M.; Sivakumar, S.; Pala, R. G. S.; Parthasarathy, G. Increased Loading of Eu3+ Ions in Monazite LaVO4 Nanocrystals via Pressure-Driven Phase Transitions. Cryst. Growth Des. 2013, 13, 2344– 2349,  DOI: 10.1021/cg3018908
      30
      Increased Loading of Eu3+ Ions in Monazite LaVO4 Nanocrystals via Pressure-Driven Phase Transitions
      Gangwar, Pooja; Pandey, Mohnish; Sivakumar, Sri; Pala, Raj Ganesh S.; Parthasarathy, G.
      Crystal Growth & Design (2013), 13 (6), 2344-2349CODEN: CGDEFU; ISSN:1528-7483. (American Chemical Society)
      The concn. of Eu3+ ion/dopant in the LaVO4 monazite nanocrystal phase cannot be increased by the conventional synthetic procedures. The authors demonstrate a unique 3-step methodol. to increase the doping concn. of Eu3+ in the LaVO4 monazite nanocrystals. In the 1st step, Eu3+ is doped (10%) in the zircon LaVO4 nanocrystal phase, which does not have a limitation in terms of Eu3+ ion loading. In the 2nd step, high pressure (∼5 GPa) is used to transform the zircon crystal phase to the monazite phase. In the 3rd step, the pressure is brought back to the atm. level, wherein the monazite crystal phase is retained in its metastable phase with the 10% Eu3+ ion doping concn. The phase transitions were characterized via elec. resistivity data, XRD, Raman spectroscopy, fluorescence spectroscopy, TEM, and d. functional simulations.
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    31. 31
      Jia, C. N.; Sun, L. D.; Yan, Z. G.; Pang, Y. C.; Lü, S. Z.; Yan, C. H. Monazite and Zircon Type LaVO4:Eu Nanocrystals – Synthesis, Luminescent Properties, and Spectroscopic Identification of the Eu3+ Sites. Eur. J. Inorg. Chem. 2010, 2010, 2626– 2635,  DOI: 10.1002/ejic.201000038
      There is no corresponding record for this reference.
    32. 32
      Nuñez, N. O.; Zambrano, P.; García-Sevillano, J.; Cantelar, E.; Rivera-Fernández, S.; De La Fuente, J. M.; Ocaña, M. Uniform Poly(Acrylic Acid)-Functionalized Lanthanide-Doped LaVO4 Nanophosphors with High Colloidal Stability and Biocompatibility. Eur. J. Inorg. Chem. 2015, 2015, 4546– 4554,  DOI: 10.1002/ejic.201500265
      There is no corresponding record for this reference.
    33. 33
      Cheng, X.; Guo, D.; Feng, S.; Yang, K.; Wang, Y.; Ren, Y.; Song, Y. Structure and Stability of Monazite- and Zircon-Type LaVO4 under Hydrostatic Pressure. Opt. Mater. (Amst). 2015, 49, 32– 38,  DOI: 10.1016/j.optmat.2015.08.011
      There is no corresponding record for this reference.
    34. 34
      Oka, Y.; Yao, T.; Yamamoto, N. Hydrothermal Synthesis of Lanthanum Vanadates: Synthesis and Crystal Structures of Zircon-Type LaVO4 and a New Compound LaV3O9. J. Solid State Chem. 2000, 152, 486– 491,  DOI: 10.1006/jssc.2000.8717
      34
      Hydrothermal Synthesis of Lanthanum Vanadates: Synthesis and Crystal Structures of Zircon-Type LaVO4 and a New Compound LaV3O9
      Oka, Yoshio; Yao, Takeshi; Yamamoto, Naoichi
      Journal of Solid State Chemistry (2000), 152 (2), 486-491CODEN: JSSCBI; ISSN:0022-4596. (Academic Press)
      In the hydrothermal synthesis of lanthanum vanadates, zircon-type LaVO4 and LaV3O9 were obtained and structurally characterized. The former is a metastable phase, and the latter is a new compd. Single-crystal x-ray diffractometry confirmed the zircon-type structure for LaVO4: space group I41/amd with a 7.4578(7), c 6.5417(9) Å, and Z = 4; R = 0.020 and Rw = 0.025 for 276 reflections with I > 3σ(I). The structure consists of isolated VO4 tetrahedra which surround the La atom to form a LaO8 dodecahedron. LaV3O9 adopts the monoclinic system: space group P21/m with a 4.949(2), b 9.547(3), c 7.411(2) Å, β 100.76(2)°, and Z = 2; R = 0.035 and Rw = 0.042 for 1868 reflections with I > 3σ(I). The structure adopts a chain-type one consisting of a V3O9 chain along [010] which is made up of edge-sharing VO5 trigonal-bipyramid pairs and VO4 tetrahedra. The La atom residues between the V3O9 chains and is coordinated with ten oxygens. The present study demonstrates the applicability of hydrothermal method to the synthesis of new and/or metastable lanthanide vanadates. (c) 2000 Academic Press.
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    35. 35
      Ropp, R. C.; Carroll, B. Precipitation of Rare Earth Vanadates from Aqueous Solution. J. Inorg. Nucl. Chem. 1977, 39, 1303– 1307,  DOI: 10.1016/0022-1902(77)80286-8
      35
      Precipitation of rare earth vanadates from aqueous solution
      Ropp, R. C.; Carroll, B.
      Journal of Inorganic and Nuclear Chemistry (1977), 39 (8), 1303-7CODEN: JINCAO; ISSN:0022-1902.
      The chem. of V in soln. was studied over the entire pH range by titrating acidic solns. of VO2+ and La3+ or Y3+ with mixed solns. of base and oxidizing agent to ppt. insol. La and Y vanadates. VO2+ was oxidized early in the titrn. to VO2+ which then condensed in soln. to form the anionic vanadate ppts. Using this method, the problem of the instability range at pH 5.5-7.5 caused by pptn. of hydrous V2O5 was avoided.
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    36. 36
      Xu, Z.; Li, C.; Hou, Z.; Peng, C.; Lin, J. Morphological Control and Luminescence Properties of Lanthanide Orthovanadate LnVO4 (Ln = La to Lu) Nano-/Microcrystals Viahydrothermal Process. CrystEngComm 2011, 13, 474– 482,  DOI: 10.1039/C0CE00161A
      There is no corresponding record for this reference.
    37. 37
      Lotfi, S.; El Ouardi, M.; Ait Ahsaine, H.; Madigou, V.; BaQais, A.; Assani, A.; Saadi, M.; Arab, M. Low-Temperature Synthesis, Characterization and Photocatalytic Properties of Lanthanum Vanadate LaVO4. Heliyon 2023, 9, e17255  DOI: 10.1016/j.heliyon.2023.e17255
      There is no corresponding record for this reference.
    38. 38
      Zhong, J.; Zhao, W. Novel Dumbbell-like LaVO4:Eu3+ Nanocrystals and Effect of Ba2+ Codoping on Luminescence Properties of LaVO4:Eu3+ Nanocrystals. J. Sol-Gel Sci. Technol. 2015, 73, 133– 140,  DOI: 10.1007/s10971-014-3504-4
      There is no corresponding record for this reference.
    39. 39
      Tian, L.; Mho, S. Enhanced Photoluminescence of YVO4:Eu3+ by Codoping the Sr2+, Ba2+ or Pb2+ Ion. J. Lumin. 2007, 122–123, 99– 103,  DOI: 10.1016/j.jlumin.2006.01.108
      There is no corresponding record for this reference.
    40. 40
      Huignard, A.; Gacoin, T.; Boilot, J. P. Synthesis and Luminescence Properties of Colloidal YVO4:Eu Phosphors. Chem. Mater. 2000, 12, 1090– 1094,  DOI: 10.1021/cm990722t
      40
      Synthesis and Luminescence Properties of Colloidal YVO4:Eu Phosphors
      Huignard, Arnaud; Gacoin, Thierry; Boilot, Jean-Pierre
      Chemistry of Materials (2000), 12 (4), 1090-1094CODEN: CMATEX; ISSN:0897-4756. (American Chemical Society)
      Concd. colloidal solns. of well-dispersed YVO4:Eu nanoparticles are synthesized by pptn. reactions at room temp. and stabilized by Na hexametaphosphate. x-ray diffraction and electron microscopy characterizations show that the cryst. nanoparticles exhibit an ellipsoidal form with 2 characteristic dimensions of ∼15 and 30 nm. In comparison with the bulk, a lower luminescence efficiency as well as a higher concn. quenching are obsd. These deviations are explained as the variations of some characteristics of the colloidal samples, such as the crystallinity and the surface chem. When these parameters are optimized, the quantum yield of the luminescence reaches 38% for the nanoparticles contg. a Eu concn. of 15%.
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    41. 41
      Deblonde, G. J. P.; Zavarin, M.; Kersting, A. B. The Coordination Properties and Ionic Radius of Actinium: A 120-Year-Old Enigma. Coord. Chem. Rev. 2021, 446, 214130  DOI: 10.1016/j.ccr.2021.214130
      41
      The coordination properties and ionic radius of actinium: A 120-year-old enigma
      Deblonde, Gauthier J.-P.; Zavarin, Mavrik; Kersting, Annie B.
      Coordination Chemistry Reviews (2021), 446 (), 214130CODEN: CCHRAM; ISSN:0010-8545. (Elsevier B.V.)
      A review. Actinium is an elusive element with untamed properties and represents a peculiar case in the periodic table, as its isotopes are all radioactive, the longest-lived one having only a 22-yr half-life, and the availability of actinium isotopes remains very low (microgram level, at best), hindering research on its compds. Despite being a natural element discovered more than 120 years ago, and despite an increasing interest in using one of its isotopes (225Ac) for highly efficient cancer therapies, the chem. of actinium is still largely unknown relative to other elements. Since Ac is the first element of the actinide series, it is accepted that its ion, Ac3+, is the most voluminous trivalent cation of the periodic table. However, the structural data available on Ac3+ compds. are scarce and have mainly been collected in the 1940-1960's, when actinide chem. was still in its infancy, and have not been put in perspective with the advances in the chem. of other elements, making it difficult to accurately evaluate its actual size and coordination chem. Herein, we review progress made on the chem. of lanthanides and actinides and reevaluate the structural data published on Ac3+ since the era of the Manhattan Project. The data are combined across different spectroscopic and characterization methods and presented in the context of periodic trends. When considering crystallog. data, soln. chem. results, and the nuclear properties of actinium isotopes, it appears that some structural parameters ascribed to the Ac3+ ion may have been overestimated. This review can guide researchers interested in actinide sciences and those who are pursuing the development of actinium-based radiotherapies, from isotope prodn. to clin. trials.
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    42. 42
      Su, J.; Mi, X.; Sun, J.; Yang, L.; Hui, C.; Lu, L.; Bai, Z.; Zhang, X. Tunable Luminescence and Energy Transfer Properties in YVO4:Bi3+, Eu3+ Phosphors. J. Mater. Sci. 2017, 52, 782– 792,  DOI: 10.1007/s10853-016-0375-9
      42
      Tunable luminescence and energy transfer properties in YVO4:Bi3+, Eu3+ phosphors
      Su, Jiangang; Mi, Xiaoyun; Sun, Jiacheng; Yang, Lixin; Hui, Chunlong; Lu, Liping; Bai, Zhaohui; Zhang, Xiyan
      Journal of Materials Science (2017), 52 (2), 782-792CODEN: JMTSAS; ISSN:0022-2461. (Springer)
      In this paper, YVO4:Bi3+, Eu3+ phosphors have been synthesized by high-temp. solid-state method. The samples were characterized by X-ray powder diffraction, photoluminescence spectra, luminescence lifetime, and GSAS structure refinement. The excitation spectrum of YVO4:Bi3+, Eu3+ monitoring at 622 nm was a broad band with major peak located at 280 nm. It contained the charge transfer from 2p orbit of O2- to 4f orbit of Eu3+ (257 nm) and the absorbing from energy level transition of Bi3+ (1S0→3P1, 346 nm) and VO43- (lA1→1T2, 286 nm and lA1→1T1, 320 nm) through gauss fitting. Upon excitation at a wavelength of 280 nm, the major emission peak of YVO4:Bi3+, Eu3+ located at 622 nm (red) was attributed to the elec. dipole transition 5D0→7F2 of Eu3+. The energy transfer mechanism of Bi3+→Eu3+ was also studied to be dipole-quadrupole mechanism of elec. multipole interaction, and the crit. distance between Eu3+ and Bi3+ was calcd. by concn. quenching method. The emission color of YVO4:Bi3+, Eu3+ can be tuned by the energy transfer of ions and the concn. of activator. In a word, the material has a good application prospects in the field of light-emitting diode under UV excitation.
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    43. 43
      Rapp, M.; Lozano, Y.; Fernández-Ramos, M.; Isasi, J.; Palafox, M. A. Superparamagnetic and Light-Emitting Bifunctional Nanocomposites of Iron Oxide and Erbium or Thulium Doped Yttrium Orthovanadate. J. Alloys Compd. 2022, 929, 167065  DOI: 10.1016/j.jallcom.2022.167065
      There is no corresponding record for this reference.
    44. 44
      Yang, L.; Li, G.; Hu, W.; Zhao, M.; Sun, L.; Zheng, J.; Yan, T.; Li, L. Control Over the Crystallinity and Defect Chemistry of YVO4 Nanocrystals for Optimum Photocatalytic Property. Eur. J. Inorg. Chem. 2011, 2011, 2211– 2220,  DOI: 10.1002/ejic.201001341
      There is no corresponding record for this reference.
    45. 45
      Wang, F.; Yu, L.; Zhu, Y.; Zhu, Z.; Meng, X.; Lv, Y.; Peng, S.; Yang, L. Defect Control and Optical Performance of Yttrium Orthovanadate Nanocrystals via a Facile PH-Sensitive Synthesis. J. Alloys Compd. 2023, 968, 172259  DOI: 10.1016/j.jallcom.2023.172259
      There is no corresponding record for this reference.
    46. 46
      Ling-Hu, P.; Guo, X.; Hu, J.; Deng, C.; Cui, R. Anomalous 5D0→7F4 Transition of Eu3+-Doped BaLaGaO4 Phosphors for WLEDs and Plant Growth Applications. Adv. Opt. Mater. 2024, 12, 2301760  DOI: 10.1002/adom.202301760
      There is no corresponding record for this reference.
    47. 47
      Chi, F.; Wei, X.; Zhou, S.; Chen, Y.; Duan, C.; Yin, M. Enhanced 5D0 → 7F4 Transition and Optical Thermometry of Garnet Type Ca3Ga2Ge3O12:Eu3+ Phosphors. Inorg. Chem. Front. 2018, 5, 1288– 1293,  DOI: 10.1039/C8QI00199E
      47
      Enhanced 5D0 → 7F4 transition and optical thermometry of garnet type Ca3Ga2Ge3O12:Eu3+ phosphors
      Chi, Fengfeng; Wei, Xiantao; Zhou, Shaoshuai; Chen, Yonghu; Duan, Changkui; Yin, Min
      Inorganic Chemistry Frontiers (2018), 5 (6), 1288-1293CODEN: ICFNAW; ISSN:2052-1553. (Royal Society of Chemistry)
      The garnet type phosphors of Eu3+ doped Ca3Ga2Ge3O12 were synthesized via conventional solid state reaction techniques. The phase purity and luminescence properties of the fabricated phosphors were characterized by X-ray powder diffraction, photoluminescence excitation and emission spectra, temp. dependent emission spectra as well as luminescence decay curves. The phosphors show enhanced red emission from a 5D0 → 7F4 transition of Eu3+ under the excitation of 394 nm. The unusual 5D0 → 7F4 intensity was explained by structural anal. The emission intensity of the phosphors increases with the concn. of Eu3+ until the quenching concn. of 10 mol%. Excited by a pulsed laser of wavelength 610.8 nm, the emission intensity of the 5D0 → 7F4 transition increases monotonously as the temp. increases in the range of 160-360 K. The temp. dependent fluorescence behavior was investigated. The relative sensitivity reaches the max. value of 3.66% K-1 at 160 K and reaches 1.04% K-1 at 300 K. The results show that the garnet type Ca3Ga2Ge3O12:Eu3+ phosphor is a promising material for the application of optical thermometry.
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    48. 48
      Shannon, R. D. Revised Effective Ionic Radii and Systematic Studies of Interatomic Distances in Halides and Chalcogenides. Acta Crystallogr., Sect. A 1976, 32, 751– 767,  DOI: 10.1107/S0567739476001551
      There is no corresponding record for this reference.
    49. 49
      Severin, A. V.; Vasiliev, A. N.; Gopin, A. V.; Vlasova, I. E.; Chernykh, E. V. Dynamics of Sorption─Desorption of 223Ra Therapeutic α-Emitter on Granulated Hydroxyapatite. Radiochemistry 2019, 61, 339– 346,  DOI: 10.1134/S1066362219030093
      There is no corresponding record for this reference.
    50. 50
      Kozempel, J.; Vlk, M.; Málková, E.; Bajzíková, A.; Bárta, J.; Santos-Oliveira, R.; Malta Rossi, A. Prospective Carriers of 223Ra for Targeted Alpha Particle Therapy. J. Radioanal. Nucl. Chem. 2015, 304, 443– 447,  DOI: 10.1007/s10967-014-3615-y
      There is no corresponding record for this reference.
    51. 51
      Suchánková, P.; Kukleva, E.; Nykl, E.; Nykl, P.; Sakmár, M.; Vlk, M.; Kozempel, J. Hydroxyapatite and Titanium Dioxide Nanoparticles: Radiolabelling and In Vitro Stability of Prospective Theranostic Nanocarriers for 223Ra and 99mTc. Nanomater. 2020, 10, 1632,  DOI: 10.3390/nano10091632
      There is no corresponding record for this reference.
    52. 52
      Suchánková, P.; Kukleva, E.; Štamberg, K.; Nykl, P.; Sakmár, M.; Vlk, M.; Kozempel, J. Determination, Modeling and Evaluation of Kinetics of 223Ra Sorption on Hydroxyapatite and Titanium Dioxide Nanoparticles. Mater. 2020, 13, 1915,  DOI: 10.3390/ma13081915
      There is no corresponding record for this reference.
    53. 53
      Kukleva, E.; Suchánková, P.; Štamberg, K.; Vlk, M.; Šlouf, M.; Kozempel, J. Surface Protolytic Property Characterization of Hydroxyapatite and Titanium Dioxide Nanoparticles. RSC Adv. 2019, 9, 21989– 21995,  DOI: 10.1039/C9RA03698A
      There is no corresponding record for this reference.
    54. 54
      Suchánková, P.; Kukleva, E.; Štamberg, K.; Nykl, P.; Vlk, M.; Kozempel, J. Study of 223Ra Uptake Mechanism on Hydroxyapatite and Titanium Dioxide Nanoparticles as a Function of PH. RSC Adv. 2020, 10, 3659– 3666,  DOI: 10.1039/C9RA08953E
      There is no corresponding record for this reference.
    55. 55
      Muckley, E. S.; Aytug, T.; Mayes, R.; Lupini, A. R.; Carrillo, J. M. Y.; Goswami, M.; Sumpter, B. G.; Ivanov, I. N. Hierarchical TiO2:Cu2O Nanostructures for Gas/Vapor Sensing and CO2 Sequestration. ACS Appl. Mater. Interfaces 2019, 11, 48466– 48475,  DOI: 10.1021/acsami.9b18824
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      Hierarchical TiO2:Cu2O Nanostructures for Gas/Vapor Sensing and CO2 Sequestration
      Muckley, Eric S.; Aytug, Tolga; Mayes, Richard; Lupini, Andrew R.; Carrillo, Jan-Michael Y.; Goswami, Monojoy; Sumpter, Bobby G.; Ivanov, Ilia N.
      ACS Applied Materials & Interfaces (2019), 11 (51), 48466-48475CODEN: AAMICK; ISSN:1944-8244. (American Chemical Society)
      We investigate the effect of high-surface-area self-assembled TiO2:Cu2O nanostructures for CO2 and relative humidity (RH) gravimetric detection using polyethylenimine (PEI), 1-ethyl-3-methylimidazolium (EMIM), and polyacrylamide (PAAm). Introduction of hierarchical TiO2:Cu2O nanostructures on the surface of quartz crystal microbalance (QCM) sensors is found to significantly improve sensitivity to CO2 and to H2O vapor. The response of EMIM to CO2 increases 5-fold for 100 nm thick TiO2:Cu2O as compared to gold. At ambient CO2 concns. the hierarchical assembly operates as a sensor with excellent reversibility, while at higher pressures the CO2 desorption rate decreases, suggesting possible application for CO2 sequestration under those conditions. The gravimetric response of PEI to CO2 increases by a factor of 3 upon introduction of a 50 nm TiO2:Cu2O layer. The PAAm gravimetric response to water vapor also increases by a factor of 3 and displays improved reversibility with the addn. of 50 nm TiO2:Cu2O structures. We found that TiO2:Cu2O can be used to lower the detection limits for CO22 sensing with EMIM and PEI and lower detection limits for H2O sensing with RAAm by over a factor of two. Coarse-grained and all-atom mol. dynamics simulations indicate the dissociative character of ionic liq. assembly on TiO2:Cu2O interfaces and different distributions of CO2 and H2O mols. on bare and ionic liq.-coated surfaces, confirming exptl. observations. Overall, our results show high potential of hierarchical assemblies of TiO2:Cu2O / room temp. ionic liq. and polymer films for sensors and CO2 sequestration.
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    56. 56
      White, F. D.; Thiele, N. A.; Simms, M. E.; Cary, S. K. Structure and Bonding of a Radium Coordination Compound in the Solid State. Nat. Chem. 2024, 16, 168– 172,  DOI: 10.1038/s41557-023-01366-z
      There is no corresponding record for this reference.
    57. 57
      Akamo, D. O.; Kumar, N.; Li, Y.; Pekol, C.; Li, K.; Goswami, M.; Hirschey, J.; LaClair, T. J.; Keffer, D. J.; Rios, O.; Gluesenkamp, K. R. Stabilization of Low-Cost Phase Change Materials for Thermal Energy Storage Applications. iScience 2023, 26, 107175  DOI: 10.1016/j.isci.2023.107175
      There is no corresponding record for this reference.
    58. 58
      Vives, S.; Ramel, D.; Meunier, C. Evolution of the Structure with the Composition and the Defect Arrangement in the Gadolinium and Samarium Doped and Co-Doped Ceria Systems: A Molecular Dynamics Study. Solid State Ionics 2021, 364, 115611  DOI: 10.1016/j.ssi.2021.115611
      There is no corresponding record for this reference.
    59. 59
      Li, P.; Merz, K. M. Metal Ion Modeling Using Classical Mechanics. Chem. Rev. 2017, 117, 1564– 1686,  DOI: 10.1021/acs.chemrev.6b00440
      59
      Metal Ion Modeling Using Classical Mechanics
      Li, Pengfei; Merz, Kenneth M., Jr.
      Chemical Reviews (Washington, DC, United States) (2017), 117 (3), 1564-1686CODEN: CHREAY; ISSN:0009-2665. (American Chemical Society)
      A review. Metal ions play significant roles in numerous fields including chem., geochem., biochem. and materials science. With computational tools increasingly becoming important in chem. research, methods have emerged to effectively face the challenge of modeling metal ions in the gas, aq. and solid phases. Herein we review both quantum and classical modeling strategies for metal ion contg. systems that have been developed over the past few decades. This review focuses on classical metal ion modeling based on unpolarized models (including the nonbonded, bonded, cationic dummy atom, and combined models), polarizable models (e.g., the fluctuating charge, Drude oscillator, and the induced dipole models), the angular overlap model, and valence bond based models. Quantum mech. studies of metal ion contg. systems at the semiempirical, ab initio and d. functional levels of theory are reviewed as well with a particular focus on how these methods inform classical modeling efforts. Finally, conclusions and future prospects and directions are offered that will further enhance the classical modeling of metal ion contg. systems.
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    60. 60
      Boll, R. A.; Malkemus, D.; Mirzadeh, S. Production of Actinium-225 for Alpha Particle Mediated Radioimmunotherapy. Appl. Radiat. Isot. 2005, 62, 667– 679,  DOI: 10.1016/j.apradiso.2004.12.003
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      Production of actinium-225 for alpha particle mediated radioimmunotherapy
      Boll, Rose A.; Malkemus, Dairin; Mirzadeh, Saed
      Applied Radiation and Isotopes (2005), 62 (5), 667-679CODEN: ARISEF; ISSN:0969-8043. (Elsevier B.V.)
      The initial clin. trials for treatment of acute myeloid leukemia demonstrated the effectiveness of the alpha emitter 213Bi in killing cancer cells. Bi-213 is obtained from a radionuclide generator system from decay of 10-days 225Ac parent. Recent pre-clin. studies also showed the potential application of both 213Bi, and the 225Ac parent radionuclide in a variety of cancer systems and targeted radiotherapy. This paper describes the 5 years of experience in prodn. of 225Ac in partial support of the on-going clin. trials. A 4-step chem. process, consisting of both anion and cation exchange chromatog., is used for routine sepn. of carrier-free 225Ac from a mixt. of 228Th, 229Th and 232Th. The sepn. of Ra and Ac from Th is achieved using the macroporous anion exchange resin MP1 in 8 M HNO3 media. Two sequential MP1/NO3 columns provide a sepn. factor of ∼106 for Ra and Ac from Th. The sepn. of Ac from Ra is accomplished on a low crosslinking cation exchange resin AG50-X4 using 1.2M HNO3 as eluant. Two sequential AG50/NO3 columns provide a sepn. factor of ∼102 for Ac from Ra. A 60-day processing schedule was adopted to reduce the processing cost and to provide the highest levels of 225Ac possible. Over an 8-wk campaign, a total of ∼100 mCi of 225Ac (∼80% of the theor. yield) is shipped in 5-6 batches, with the 1st batch typically consisting of ∼50 mCi. After the initial sepn. and purifn. of Ac, the Ra pool is re-processed on a bi-weekly schedule or as needed to provide smaller batches of 225Ac. The averaged radioisotopic purity of the 225Ac was 99.6 ± 0.7% with a 225Ra content of ≤0.6%, and an av. 229Th content of (4+5-4)×10-5%.
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    61. 61
      Huignard, A.; Buissette, V.; Laurent, G.; Gacoin, T.; Boilot, J. P. Synthesis and Characterizations of YVO4: Eu Colloids. Chem. Mater. 2002, 14, 2264– 2269,  DOI: 10.1021/cm011263a
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      Synthesis and Characterizations of YVO4:Eu Colloids
      Huignard, A.; Buissette, V.; Laurent, G.; Gacoin, T.; Boilot, J. P.
      Chemistry of Materials (2002), 14 (5), 2264-2269CODEN: CMATEX; ISSN:0897-4756. (American Chemical Society)
      A new process for the synthesis of colloidal Eu-doped YVO4 with a particle diam. of ∼10 nm is presented. Nanocrystals are produced by pptn. of citrate complexes of rare earth salts with Na3VO4. NMR and IR studies show that the interaction between citrate ligands and lanthanide ions limits the growth of particles and ensures the stability of the colloidal solns. through electrostatic and steric repulsions. The optimized process leads to stable and highly concd. transparent colloidal solns. in H2O (≤400 g/L).
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    62. 62
      Young, R. A.. The Rietveld Method; Oxford University Press, 1981.
      There is no corresponding record for this reference.
    63. 63
      Toby, B. H.; Von Dreele, R. B. GSAS-II: The Genesis of a Modern Open-Source All Purpose Crystallography Software Package. J. Appl. Crystallogr. 2013, 46, 544– 549,  DOI: 10.1107/S0021889813003531
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      GSAS-II: the genesis of a modern open-source all purpose crystallography software package
      Toby, Brian H.; Von Dreele, Robert B.
      Journal of Applied Crystallography (2013), 46 (2), 544-549CODEN: JACGAR; ISSN:0021-8898. (International Union of Crystallography)
      The newly developed GSAS-II software is a general purpose package for data redn., structure soln. and structure refinement that can be used with both single-crystal and powder diffraction data from both neutron and x-ray sources, including lab. and synchrotron sources, collected on both two- and 1-dimensional detectors. It is intended that GSAS-II will eventually replace both the GSAS and the EXPGUI packages, as well as many other utilities. GSAS-II is open source and is written largely in object-oriented Python but offers speeds comparable to compiled code because of its reliance on the Python NumPy and SciPy packages for computation. It runs on all common computer platforms and offers highly integrated graphics, both for a user interface and for interpretation of parameters. The package can be applied to all stages of crystallog. anal. for const.-wavelength x-ray and neutron data. Plans for considerable addnl. development are discussed.
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    64. 64
      Thompson, A. P.; Aktulga, H. M.; Berger, R.; Bolintineanu, D. S.; Brown, W. M.; Crozier, P. S.; in’t Veld, P. J.; Kohlmeyer, A.; Moore, S. G.; Nguyen, T. D.; Shan, R.; Stevens, M. J.; Tranchida, J.; Trott, C.; Plimpton, S. J. LAMMPS - a Flexible Simulation Tool for Particle-Based Materials Modeling at the Atomic, Meso, and Continuum Scales. Comput. Phys. Commun. 2022, 271, 108171  DOI: 10.1016/j.cpc.2021.108171
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      LAMMPS - a flexible simulation tool for particle-based materials modeling at the atomic, meso, and continuum scales
      Thompson, Aidan P.; Aktulga, H. Metin; Berger, Richard; Bolintineanu, Dan S.; Brown, W. Michael; Crozier, Paul S.; in 't Veld, Pieter J.; Kohlmeyer, Axel; Moore, Stan G.; Nguyen, Trung Dac; Shan, Ray; Stevens, Mark J.; Tranchida, Julien; Trott, Christian; Plimpton, Steven J.
      Computer Physics Communications (2022), 271 (), 108171CODEN: CPHCBZ; ISSN:0010-4655. (Elsevier B.V.)
      Since the classical mol. dynamics simulator LAMMPS was released as an open source code in 2004, it has become a widely-used tool for particle-based modeling of materials at length scales ranging from at. to mesoscale to continuum. Reasons for its popularity are that it provides a wide variety of particle interaction models for different materials, that it runs on any platform from a single CPU core to the largest supercomputers with accelerators, and that it gives users control over simulation details, either via the input script or by adding code for new interat. potentials, constraints, diagnostics, or other features needed for their models. As a result, hundreds of people have contributed new capabilities to LAMMPS and it has grown from fifty thousand lines of code in 2004 to a million lines today. In this paper several of the fundamental algorithms used in LAMMPS are described along with the design strategies which have made it flexible for both users and developers. We also highlight some capabilities recently added to the code which were enabled by this flexibility, including dynamic load balancing, on-the-fly visualization, magnetic spin dynamics models, and quantum-accuracy machine learning interat. potentials.Program Title: Large-scale Atomic/Mol. Massively Parallel Simulator (LAMMPS)CPC Library link to program files:https://doi.org/10.17632/cxbxs9btsv.1Developer's repository link:https://github.com/lammps/lammpsLicensing provisions: GPLv2Programming language: C++, Python, C, FortranSupplementary material:https://www.lammps.orgNature of problem: Many science applications in physics, chem., materials science, and related fields require parallel, scalable, and efficient generation of long, stable classical particle dynamics trajectories. Within this common problem definition, there lies a great diversity of use cases, distinguished by different particle interaction models, external constraints, as well as timescales and lengthscales ranging from at. to mesoscale to macroscopic.Soln. method: The LAMMPS code uses parallel spatial decompn., distributed neighbor lists, and parallel FFTs for long-range Coulombic interactions [1]. The time integration algorithm is based on the Stormer-Verlet symplectic integrator [2], which provides better stability than higher-order non-symplectic methods. In addn., LAMMPS supports a wide range of interat. potentials, constraints, diagnostics, software interfaces, and pre- and post-processing features.Addnl. comments including restrictions and unusual features: This paper serves as the definitive ref. for the LAMMPS code.S. Plimpton, Fast parallel algorithms for short-range mol. dynamics. Phys. 117 (1995) 1-19.L. Verlet, Computer expts. on classical fluids: I. Thermodynamical properties of Lennard-Jones mols., Phys. Rev. 159 (1967) 98-103.
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    65. 65
      Martinez, L.; Andrade, R.; Birgin, E. G.; Martínez, J. M. PACKMOL: A Package for Building Initial Configurations for Molecular Dynamics Simulations. J. Comput. Chem. 2009, 30, 2157– 2164,  DOI: 10.1002/jcc.21224
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      PACKMOL: A package for building initial configurations for molecular dynamics simulations
      Martinez, L.; Andrade, R.; Birgin, E. G.; Martinez, J. M.
      Journal of Computational Chemistry (2009), 30 (13), 2157-2164CODEN: JCCHDD; ISSN:0192-8651. (John Wiley & Sons, Inc.)
      Adequate initial configurations for mol. dynamics simulations consist of arrangements of mols. distributed in space in such a way to approx. represent the system's overall structure. In order that the simulations are not disrupted by large van der Waals repulsive interactions, atoms from different mols. must keep safe pairwise distances. Obtaining such a mol. arrangement can be considered a packing problem: Each type mol. must satisfy spatial constraints related to the geometry of the system, and the distance between atoms of different mols. must be greater than some specified tolerance. We have developed a code able to pack millions of atoms, grouped in arbitrarily complex mols., inside a variety of three-dimensional regions. The regions may be intersections of spheres, ellipses, cylinders, planes, or boxes. The user must provide only the structure of one mol. of each type and the geometrical constraints that each type of mol. must satisfy. Building complex mixts., interfaces, solvating biomols. in water, other solvents, or mixts. of solvents, is straightforward. In addn., different atoms belonging to the same mol. may also be restricted to different spatial regions, in such a way that more ordered mol. arrangements can be built, as micelles, lipid double-layers, etc. The packing time for state-of-the-art mol. dynamics systems varies from a few seconds to a few minutes in a personal computer. The input files are simple and currently compatible with PDB, Tinker, Molden, or Moldy coordinate files. The package is distributed as free software and can be downloaded from . © 2009 Wiley Periodicals, Inc. J Comput Chem, 2009.
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      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD1MXptleqsb8%253D&md5=2a76255c873b866a26540f7e84496272
    66. 66
      Qiao, B.; Skanthakumar, S.; Soderholm, L. Comparative CHARMM and AMOEBA Simulations of Lanthanide Hydration Energetics and Experimental Aqueous-Solution Structures. J. Chem. Theory Comput. 2018, 14, 1781– 1790,  DOI: 10.1021/acs.jctc.7b01018
      66
      Comparative CHARMM and AMOEBA Simulations of Lanthanide Hydration Energetics and Experimental Aqueous-Solution Structures
      Qiao, Baofu; Skanthakumar, S.; Soderholm, L.
      Journal of Chemical Theory and Computation (2018), 14 (3), 1781-1790CODEN: JCTCCE; ISSN:1549-9618. (American Chemical Society)
      The accurate understanding of metal ion hydration in solns. is a prerequisite for predicting stability, reactivity, and soly. Herein, additive CHARMM force field parameters were developed to enable mol. dynamics simulations of lanthanide (Ln) speciation in water. Quant. similar to the much more resource-intensive polarizable AMOEBA potential, the CHARMM simulations reproduce the exptl. hydration free energies and correlations in the first shell (Ln-oxygen distance and hydration no.). Comparisons of difference pair-distribution functions obtained from the two simulation approaches with those from high-energy x-ray scattering expts. reveal good agreement of first-coordination sphere correlations for the Lu3+ ion (CHARMM only), but further improvement to both approaches is required to reproduce the broad, non-Gaussian distribution seen from the La3+ expt. Second-coordination sphere comparisons demonstrate the importance of explicitly including an anion in the simulation. This work describes the usefulness of less resource-intensive additive potentials in some complex chem. systems such as soln. environments where multiple interactions have similar energetics. In addn., 3-dimensional descriptions of the La3+ and Lu3+ coordination geometries are extd. from the CHARMM simulations and generally discussed in terms of potential improvements to solute-structure modeling within soln. environments.
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      Priest, C.; Zhou, J.; Jiang, D.; en Solvation of the Vanadate Ion in Seawater Conditions from Molecular Dynamics Simulations. Inorg. Chim. Acta 2017, 458, 39– 44,  DOI: 10.1016/j.ica.2016.12.027
      67
      Solvation of the vanadate ion in seawater conditions from molecular dynamics simulations
      Priest, Chad; Zhou, Jingwei; Jiang, De-en
      Inorganica Chimica Acta (2017), 458 (), 39-44CODEN: ICHAA3; ISSN:0020-1693. (Elsevier B.V.)
      One of the current challenges present in uranium extn. from seawater is the competitive sorption of vanadium. But compared with uranium, much less is known about the solvation and speciation of the vanadate ion in seawater. Herein, we utilize both first principles mol. dynamics and classical mol. dynamics simulations to provide a microscopic insight into the solvation of the HVO42- ion in pure water and in seawater. In pure water, we found that the dianion state is the most probable structure. But in a simulated seawater with 0.55 M NaCl, the NaHVO4- ion is most probable, followed by the neutral Na2HVO4; averaging over 100-ns trajectory, the coordination no. of Na+ ions around V was found to be 1.5 within a radius of 4.0 Å. We found that the NaHVO4- ion can exist in two interchangeable states: a bidentate state where the Na+ ion interacts directly with two vanadate oxo groups; a monodentate where the Na+ ion interacts with only one vanadate oxo group. From this monodentate state, the Na+ ion can further dissoc. away with a free-energy barrier of 2.5 kcal/mol. Our work therefore demonstrates that Na+ ions are closely assocd. with the vanadate species in seawater.
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      Clark, G. N. I.; Cappa, C. D.; Smith, J. D.; Saykally, R. J.; Head-Gordon, T. The Structure of Ambient Water. Mol. Phys. 2010, 108, 1415– 1433,  DOI: 10.1080/00268971003762134
      68
      The structure of ambient water
      Clark, Gary N. I.; Cappa, Christopher D.; Smith, Jared D.; Saykally, Richard J.; Head-Gordon, Teresa
      Molecular Physics (2010), 108 (11), 1415-1433CODEN: MOPHAM; ISSN:0026-8976. (Taylor & Francis Ltd.)
      We review the spectroscopic techniques and scattering expts. used to probe the structure of water, and their interpretation using empirical and ab initio models, over the last 5 years. We show that all available scientific evidence overwhelmingly favors the view of classifying water near ambient conditions as a uniform, continuous tetrahedral liq. While there are controversial issues in our understanding of water in the supercooled state, in confinement, at interfaces, or in soln., there is no real controversy in what is understood as regards bulk liq. water under ambient conditions.
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    69. 69
      Goswami, M.; Kumar, N.; Li, Y.; Hirschey, J.; LaClair, T. J.; Akamo, D. O.; Sultan, S.; Rios, O.; Gluesenkamp, K. R.; Graham, S. Understanding Supercooling Mechanism in Sodium Sulfate Decahydrate Phase-Change Material. J. Appl. Phys. 2021, 129, 245109  DOI: 10.1063/5.0049512
      There is no corresponding record for this reference.

  • Supporting Information

    Supporting Information

    The Supporting Information is available free of charge at https://pubs.acs.org/doi/10.1021/acsnano.3c13213.

    • Description of MD simulations in detail; force-field parameters (Lennard-Jones) used in the MD simulations; RDF of water in LnVO4 and the comparison of the RDF of La, Eu, and oxygen of VO4; RDF of Ac-/Ra-doped lanthanide at different temperatures and the snapshots; Rietveld analysis parameters and XRD patterns; summary of the molar ratio of the nanoconstructs; excitation and emission spectra of 225Ac-doped nanoconstructs and 30 days' decayed 225Ac-doped nanoconstructs, respectively; and different compositions of lanthanides (PDF)


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