PULSED GRADIENT FIELD STUDY OF NANOSIZED RHENIUM COMPLEXES

Radiopharmaceuticals incorporating 99mTc and 186/188Re have been extensively studied in the last decades [1]. Suitable nuclear properties of these metals can be exploited for both diagnosis (99mTc) and therapy (186/188Re). Among the different fragments introduced into the radiopharmaceuticals, great interest has gained the aquo complex [M(H2O)3(CO)3]+ (M = Re, Tc), that contains three labile water molecules together with a stable fac M(CO)3+ core, suitable for bio-conjugation. To test the feasibility and stability of the bioconjugates, experiments are normally performed using the cold rhenium natural isotopic mixture as surrogate. Different chelating agents as well as different coordination routes have been proposed in order to get rhenium derivatives with high specificity and stability [2]. In this communication we show the results obtained by reacting [Re(H2O)3(CO)3]+ with highly hydrosoluble polymers, suitable for the use as biomedical materials. A detailed study on the polymer size, in the presence and in the absence of rhenium, has been performed by means of longitudinal relaxation (T1) times and pulsed gradient spin echo (PGSE) NMR experiments [3]. 1H PGSE NMR experiments have been performed at room temperature on diluted sample, at different ionic strength and different pH, to evaluate the influence of these parameters on polymer aggregations. Stimulated echo sequences, incorporating bipolar gradient pulses, were used, both with and without water suppression. Through these methods, diffusion coefficients have been determined and the hydrodynamic radii rH of the random polymers, with and without rhenium, have been estimated. Comparison with results obtained by dynamic light scattering measurements will be provided. References [1] See for instance U. Mazzi and M. Riondato Recent development in Bioinorganic Chemistry 1-33 (2006) [2] See for instance R. Alberto, R. Schibli, R. Waibel, U. Abram and A. P. Schubiger Coord. Chem. Rev. 190-192, 901-919 (1999) [3] See for instance A. Macchioni, G. Ciancaleoni, C. Zuccaccia and D. Zuccaccia Chem. Soc. Rev. 37, 479-489 (2008)