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Saint-Herblain, France

Pniok M.,Charles University | Kubicek V.,Charles University | Havlickova J.,Charles University | Kotek J.,Charles University | And 6 more authors.
Chemistry - A European Journal | Year: 2014

Diethylenetriamine-N,N,N′,N′′,N′′-pentaacetic acid (DTPA) and 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid (DOTA) scandium(III) complexes were investigated in the solution and solid state. Three 45Sc NMR spectroscopic references suitable for aqueous solutions were suggested: 0.1-M Sc(ClO4)3 in 1-M aq. HClO4 (δSc=0.0 ppm), 0.1-M ScCl3 in 1-M aq. HCl (δSc=1.75 ppm) and 0.01-M [Sc(ox)4] 5- (ox2-=oxalato) in 1-M aq. K2C 2O4 (δSc=8.31 ppm). In solution, [Sc(dtpa)]2- complex (δSc=83 ppm, β-μ ν=770 Hz) has a rather symmetric ligand field unlike highly unsymmetrical donor atom arrangement in [Sc(dota)]- anion (δSc=100 ppm, β-μ ν=4300 Hz). The solid-state structure of K 8[Sc2(ox)7]·13-H2O contains two [Sc(ox)3]3- units bridged by twice "side-on" coordinated oxalate anion with Sc3+ ion in a dodecahedral O 8 arrangement. Structures of [Sc(dtpa)]2- and [Sc(dota)]- in [(Hguanidine)]2[Sc(dtpa)]·3-H 2O and K[Sc(dota)][H6dota]Cl2·4-H 2O, respectively, are analogous to those of trivalent lanthanide complexes with the same ligands. The [Sc(dota)]- unit exhibits twisted square-antiprismatic arrangement without an axial ligand (TSA′ isomer) and [Sc(dota)]- and (H6dota)2+ units are bridged by a K+ cation. A surprisingly high value of the last DOTA dissociation constant (pKa=12.9) was determined by potentiometry and confirmed by using NMR spectroscopy. Stability constants of scandium(III) complexes (log KScL 27.43 and 30.79 for DTPA and DOTA, respectively) were determined from potentiometric and 45Sc NMR spectroscopic data. Both complexes are fully formed even below pH 2. Complexation of DOTA with the Sc3+ ion is much faster than with trivalent lanthanides. Proton-assisted decomplexation of the [Sc(dota)]- complex (τ1/2=45 h; 1-M aq. HCl, 25-°C) is much slower than that for [Ln(dota)]- complexes. Therefore, DOTA and its derivatives seem to be very suitable ligands for scandium radioisotopes. New Sc3+ carrier delivers: Complexes of trivalent scandium with 1,4,7,10-tetraazacyclododecane-1, 4,7,10-tetraacetic acid (DOTA) and diethylenetriamine-N,N,N′, N′′,N′′-pentaacetic acid (DTPA) were investigated in solution and in the solid state. Potentiometry and multinuclear NMR spectrometry revealed relatively fast complexation of Sc3+ with DOTA, as well as very high stability constants and high kinetic inertness for the complex. The data confirmed that DOTA-like ligands are very suitable for the development of scandium-based radiopharmaceuticals (see figure). © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. Source

Traboulsi A.,CNRS Laboratory of Subatomic Physics and Associated Technologies | Vandenborre J.,CNRS Laboratory of Subatomic Physics and Associated Technologies | Blain G.,CNRS Laboratory of Subatomic Physics and Associated Technologies | Humbert B.,Jean Rouxel Institute | And 2 more authors.
Journal of Physical Chemistry C | Year: 2014

In this work, the oxidative corrosion of UO2 particles by molecular species produced by 4He2+ radiolysis of water (simulated by irradiation with a 4He2+ beam) has been investigated as a function of the absorbed dose under open and closed atmospheres. This work was carried out by coupling for the first time (1) characterization of the UO2 surface after oxidation, (2) analysis of H2 and H2O2 produced by water radiolysis, and (3) quantification of the uranium species leached into the solution during irradiation. Oxidation of the surface of the UO2 particles was characterized by Raman spectroscopy. H2 and H2O 2 were analyzed by micro gas chromatography and UV-vis spectrophotometry, respectively. Inductively coupled plasma mass spectrometry was used to quantify the soluble uranium species released into the solution. The results showed that, when the ultrapure water above the UO2 particles was irradiated in an open atmosphere, metastudtite was formed on the UO2 surface, indicating its oxidation by the H2O 2 produced by water radiolysis. This oxidation was accompanied by migration of soluble uranium species [U(VI)] into the irradiated solution. After irradiation in a closed atmosphere, oxidation of the UO2 surface and migration of soluble uranium species were limited due to the presence of H 2. The inhibition does not occur by direct effect of H2 on H2O2 but more probably by adsorption of H2 molecules on the UO2 surface. © 2013 American Chemical Society. Source

Crumiere F.,Ecole des Mines de Nantes | Vandenborre J.,Ecole des Mines de Nantes | Essehli R.,Ecole des Mines de Nantes | Blain G.,Ecole des Mines de Nantes | And 2 more authors.
Radiation Physics and Chemistry | Year: 2013

Radiation chemical primary yields g(H2) have been determined for irradiations performed with 60Co γ-rays source of LCP (Orsay, France) and with helium ion beams (Eα=5.0MeV-64.7MeV) using protective agent bromide anions in solution. The α (4He2+) irradiation experiments were performed either at CEMHTI or at the new ARRONAX cyclotron facility (2010). Both sources (γ and cyclotrons) allow working with a large LET value range between 0.23 and 151.5keV/μm. On one hand, the obtained results have been compared with those available in the literature and plotted as a function of the LET parameter in order to discuss the effects of track structure on the production of molecular hydrogen. On the other hand, the primary radiation chemistry yield g(H2) values are compared with global radiation chemical yields G(H2) obtained during irradiations of pure water irradiated under air or argon without scavenging. For each system, it appears that radiation chemical yields increase with the LET value. Our results suggest that using bromide anions, at low concentration, as a protective agent becomes ineffective when the LET value used is higher than 120±20keV/μm. © 2012 Elsevier Ltd. Source

Du A.L.,CNRS Laboratory of Subatomic Physics and Associated Technologies | Mougin-Degraef M.,University of Nantes | Botosoa E.,University of Nantes | Rauscher A.,University of Nantes | And 3 more authors.
Radiochimica Acta | Year: 2011

Indium-DTPA-tagged liposomes were studied in the present work as carriers of in vivo 212Pb/212Bi generator to be used in targeted alpha therapy. The liposomal uptake of 212Pb, into preformed liposomes, was investigated using different lipophilic chelate (DCP, 2,3-dimercapto-1-propanol (BAL), sodium acetate, and A23187), as a function of various parameters (temperature, concentrations of lipids, Pb, DTPA, ...) with 212Pb as a tracer.Different formulations of liposomes were tested to evaluate the radiolabeling efficiency. No complexing agent was necessary for the passage of Pb2+ through the membrane. It occurs naturally via a partial permeability of the lipid bilayer, which increases with the temperature. Acomplexing agent (DTPA) appears necessary to concentrate Pb in the internal compartment of the liposomes. Conditions were found (T = 65 °C, internal DTPA concentration of 0.025 M, pH 7.4, ...) yielding a high and rapid uptake of 212Pb in liposomes. The protocol established provides a novelmethod for the efficient entrapment of about 2-3 Pb atoms per liposome with a yield of 75% in conditions relevant for nuclear medicine. © by Oldenbourg Wissenschaftsverlag, München. Source

Denden I.,CNRS Laboratory of Subatomic Physics and Associated Technologies | Poineau F.,University of Nevada, Las Vegas | Schlegel M.L.,CEA Saclay Nuclear Research Center | Roques J.,University Paris - Sud | And 6 more authors.
Journal of Physical Chemistry A | Year: 2014

The effect of α-radiolysis on the behavior of heptavalent technetium has been investigated in 13 and 18 M H2SO4. Irradiation experiments were performed using α-particles (4He2+, E = 68 MeV) generated by the ARRONAX cyclotron. UV-visible and X-ray absorption fine structure spectroscopic studies indicate that Tc(VII) is reduced to Tc(V) under α-irradiation. Extended X-ray absorption fine structure (EXAFS) spectroscopy measurements are consistent with the presence of mononuclear technetium sulfate complexes. Experimental results and density functional calculations show the formation of [TcO(HSO4)3(H 2O)(OH)]- and/or [TcO(HSO4)3(H 2O)2] and [Tc(HSO4)3(SO 4)(H2O)] and/or [Tc(HSO4)3(SO 4)(OH)]- for 13 and 18 M H2SO4, respectively. © 2014 American Chemical Society. Source

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