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2010-10-20 - Colloque/Présentation - poster - Anglais - 1 page(s)

Zhou Qiuju, Henoumont Céline , Vander Elst Luce , Laurent Sophie , Muller Robert , "Quantitative determination of the presence of free gallium ions in solutions of Ga-complexes by 71Ga NMR" in 32nd discussion meeting and joint Benelux/german MR conference, Allemagne, 2010

  • Codes CREF : Résonance magnétique nucléaire (biophysique) (DI131B), Chimie de coordination (DI1319), Chimie (DI1300)
  • Unités de recherche UMONS : Chimie générale, organique et biomédicale (M108)
  • Instituts UMONS : Institut des Sciences et Technologies de la Santé (Santé), Institut des Biosciences (Biosciences)

Abstract(s) :

(Anglais) Ga-complexes are invaluable tools as probes for imaging studies with 66Ga, 67Ga, or 68Ga radiopharmaceuticals, and as therapeutic agents for the treatment of a number of cancer and infectious diseases with non-radioactive gallium compounds [1]. Their use relies on the assumption that the solutions are not contaminated by the presence of free Ga3+ ions. These free Ga3+ ions can indeed have a deep effect on the efficacy of the gallium agents as they are likely to be hydrolysed in [Ga(OH)4]- [2] or to be uptaken by iron-binding proteins [3]. Therefore any Ga complex should be carefully checked for the free gallium ions before use. 71Ga NMR could be an interesting technique to rapidly detect the presence of these undesirable ions in the solutions of the Ga-complexes. 71Ga NMR is less spread among the liquid NMR community, the main cause being probably the broad peaks generally exhibited. 71Ga is indeed a nucleus of spin 3/2 with a large quadrupolar moment of 0.112 x 10-28 m2 [4]. Only resonances of Ga in a highly symmetrical local environment are sharp enough to be detected [5]. Free gallium ions can however be detected at acidic pH as [Ga(H2O)6]3+ and at neutral or basic pH as [Ga(OH)4]- [2, 6]. In a preliminary study, a solution of Ga-DOTA 50 mM at pH 7.5 contaminated by free gallium ions has been studied. Two peaks were observed on the 71Ga NMR spectra, a large one at around 137 ppm which corresponds to gallium incorporated in the complex and a sharp one at 223 ppm corresponding to free gallium in the form of [Ga(OH)4]-. The chemical shifts are expressed with respect to the absorption of an external reference composed of Ga(NO3)3 at an acidic pH. This reference was also to estimate the amount of free gallium in the solution of Ga-DOTA. The influence of pH and molecular tumbling on the Gallium chemical shifts and relaxation times have been studied. References (1) Bandoli, G.; Dolmella, A.; Tisato, F.; Porchia, M.; Refosco, F. Coord. Chem. Rev. 2009, 253, 56-77. (2) Akitt, J. W.; Kettle, D. Magn. Reson. Chem. 1989, 27, 377-379. (3) Aramini, J. M.; Mcintyre, D. D.; Vogel, H. J. J. Am. Chem. Soc. 1994, 116, 11506-11511. (4) Andre, J. P.; Macke, H. R. J. Inorg. Biochem. 2003, 97, 315-323. (5) Glickson, J. D.; Pitner, T. P.; Webb, J.; Gams, R. A. J. Am. Chem. Soc. 1975, 97, 1679-1683. (6) Garcia, R.; Fouskova, P.; Gano, L.; Paulo, A.; Campello, P.; Toth, E.; Santos, I. J. Biol. Inorg. Chem. 2009, 14, 261-271.