Medical effects of internal contamination with actinides: further controversy on depleted uranium and radioactive warfare

Preparation and Evaluation of a Combination of Chelating Agents for the Removal of Inhaled Uranium

Inhalation of aerosolized uranium is recognized as a principal mode of exposure, posing significant risks of damage to the lungs, kidneys, and other vital organs. To enhance nuclide elimination from the body, chelating agents are employed; however, single-component chelators often exhibit limited spectral activity and low effectiveness, resulting in toxicologically relevant concentrations. We have developed a composite chelating agent composed of 3,4,3-Li(1,2-HOPO), DFP, and HEDP in optimized ratios, demonstrating marked improvements in eliminating inhaled uranium. The selection of these components was initially guided by an agarose gel dynamics method, focusing on uranium binding and removal efficacy. Optimization of the formula was conducted through response surface methodology in a cellular model. The compound's ability to enhance survival rates in mice subjected to acute uranium inhalation was confirmed, showing a dose-dependent improvement in survival in severely affected mice. Comparative assessments indicated that this multifaceted chelating agent substantially surpasses the uranium tissue clearance achieved by individual chelating agents.

α-Aminobisphosphonate Copolymers Based on Poly(ε-caprolactone)s and Poly(ethylene glycol): A New Opportunity for Actinide Complexation

Original α-aminobisphosphonate-based copolymers were synthesized and successfully used for actinide complexation. For this purpose, poly(α-chloro-ε-caprolactone-co-ε-caprolactone)-b-poly(ethylene glycol)-b-poly(α-chloro-ε-caprolactone-co-ε-caprolactone) copolymers were first prepared by ring-opening copolymerization of ε-caprolactone (εCL) and α-chloro-ε-caprolactone using poly(ethylene glycol) (PEG) as a macro-initiator and tin(II) octanoate as a catalyst. The chloride functions were then converted to azide moieties by chemical modification, and finally α-aminobisphosphonate alkyne ligand (TzBP) was grafted using click chemistry, to afford well-defined poly(αTzBPεCL-co-εCL)-b-PEG-b-poly(αTzBPεCL-co-εCL) copolymers. Three copolymers, showing different α-aminobisphosphonate group ratios, were prepared (7, 18, and 38%), namely, CP8, CP9, and CP10, respectively. They were characterized by 1H and 31P NMR and size exclusion chromatography. Sorption properties of these copolymers were evaluated by isothermal titration calorimetry (ITC) with neodymium [Nd(III)] and cerium [Ce(III)] cations, used as surrogates of actinides, especially uranium and plutonium, respectively. ITC enabled the determination of the full thermodynamic profile and the calculation of the complete set of thermodynamic parameter (ΔH, TΔS, and ΔG), with the Ka constant and the n stoichiometry. The results showed that the number of cations sorbed by the functional copolymers logically increased with the number of bisphosphonate functions borne by the macromolecular chain, independently of the complexed cation. Additionally, CP9 and CP10 copolymers showed higher sorption capacities [21.4 and 34.0 mg·g-1 for Nd(III) and 9.6 and 14.3 mg·g-1 for Ce(III), respectively] than most of the systems previously described in the literature. CP9 also showed a highest binding constant (7000 M-1). These copolymers, based on non-toxic and biocompatible poly(ε-caprolactone) and PEG, are of great interest for external body decontamination of actinides as they combine high number of complexing groups, thus leading to great decontamination efficiency, and limited diffusion through the skin due to their high-molecular weight, thus avoiding additional possible internal contamination.

Structure and Characterization of an Americium Bis(O,O'-diethyl)dithiophosphate Complex

A facile synthesis of an americium complex with a sulfur-donor ligand has been developed, allowing characterization of americium bonding from multiple perspectives via several techniques. Reaction of ²⁴³Am with S₂P(OEt)₂^- yields the tetrakis complex [Am(S₂P(OEt)₂)₄]^- that can be crystallized as the tetraphenylarsonium salt. Structures obtained from single crystal X-ray diffraction show bond length discrepancies from the neodymium analogue consistent with the soft-donor bond enhancement common to actinides. Solid state optical spectroscopy confirms interaction of the ligand with 5f orbitals. ³¹P nuclear magnetic reflects the minor paramagnetism of Am(III). Computational investigations through CASSCF calculations, ligand-field density functional theory, and quantum chemical topological analysis allow a quantification of covalency or orbital interaction effects via total energy density and nephelauxetic parameters, both of which indicate greater covalency in the americium species than in the neodymium analogue or the americium aquo complex.

Periodic trends and complexation chemistry of tetravalent actinide ions with a potential actinide decorporation agent 5-LIO(Me-3,2-HOPO): A relativistic density functional theory exploration

A relativistic density functional theory (DFT) study is reported which aims to understand the complexation chemistry of An⁴⁺ ions (An = Th, U, Np, and Pu) with a potential decorporation agent, 5-LIO(Me-3,2-HOPO). The calculations show that the periodic change of the metal binding free energy has an excellent correlation with the ionic radii and such change of ionic radii also leads to the structural modulation of actinide-ligand complexes. The calculated structural and binding parameters agree well with the available experimental data. Atomic charges derived from quantum theory of atoms in molecules (QTAIM) and natural bond order (NBO) analysis shows the major role of ligand-to-metal charge transfer in the stability of the complexes. Energy decomposition analysis, QTAIM, and electron localization function (ELF) predict that the actinide-ligand bond is dominantly ionic, but the contribution of orbital interaction is considerable and increases from Th⁴⁺ to Pu⁴⁺ . A decomposition of orbital contributions applying the extended transition state-natural orbital chemical valence method points out the significant π-donation from the oxygen donor centers to the electron-poor actinide ion. Molecular orbital analysis suggests an increasing trend of orbital mixing in the context of 5f orbital participation across the tetravalent An series (Th-Pu). However, the corresponding overlap integral is found to be smaller than in the case of 6d orbital participation. An analysis of the results from the aforementioned electronic structure methods indicates that such orbital participation possibly arises due to the energy matching of ligand and metal orbitals and carries the signature of near-degeneracy driven covalency.

Depleted uranium and Gulf War Illness: Updates and comments on possible mechanisms behind the syndrome

Indications of proximal tubule effects have been observed in recent surveillance study of Gulf War veterans exposed to depleted uranium (DU). This gives some support for the suspicion that DU may represent one of the causes for the so-called Persian Gulf syndrome. Proposed effects may be especially harmful if the toxicity hits the mitochondrial DNA since the mitochondria lack the nucleotide excision repair mechanism, which is needed for repairing bulky adducts that have been associated with DU. It is a plausible working hypothesis that a significant part of the symptoms from various organs, which have been observed among veterans from Gulf War 1 and that have been grouped under the name of the Persian Gulf syndrome, may be explained as a consequence of mitochondrial DNA damage in various cell types and organs. Interpretation of observations, on military personnel and civilians after Gulf War 1, is associated with difficulties because of the abundance of potential confounding factors. The symptoms observed on veterans from Gulf War 1 may be attributed to a multiplicity of substances functioning directly or indirectly as mitochondrial mutagens. A concise analysis of the cascade of toxic effects initiated by DU exposure in the human body is the subject of this article.