An experimental study of sorption/desorption of selected radionuclides on carbon nanomaterials: a quest for possible applications in future nuclear medicine

In this study, the possibility of application of carbon nanomaterials (CNMs) as carriers of various isotopes for nuclear medicine is investigated. The sorption of Tc-99m, Bi-207 (as analog for Bi-213), Y-90, and Ra-226 (as analog for Ra-223) in aqueous solutions with pH 6 and 0.01 M phosphate-buffered saline with pH 7 was studied on the following CNMs samples: detonation nanodiamonds (NDs), reduced graphite oxide (rGiO), and multi-walled nanotubes (MWCNTs). Commercial, hydrogenated, and aminated ND and hydrogenated MWCNTs adsorb Tc (VII) by 40-70%; however, in physiological saline, it is readily desorbed within 0.5 h. The sorption of Tc(IV) on commercial and carboxylated ND, as well as rGiO, was 60-90%. In this case, desorption in the biological media did not exceed 5% for each sample in 5 h. The sorption of Bi(III) on all the samples studied was from 80% to 100%, and the Bi(III)@ND conjugate was the most stable, as its desorption in the model biological medium was 4% for 5 h. It was shown that the sorption and desorption for Y(III) differs significantly depending on the CNM sample used, thereby allowing for the selection of the conditions for the use of Y(III)@CNMs conjugate for specific medical tasks. It was found that Ra(II) sorption occurs only on the rGiO sample and reaches 60%; however, depending on the medium, desorption was from 35% to 70% in 30 min, thereby complicating the use of the Ra(II)@rGiO conjugate. The data regarding sorption behavior and stability in biological media of the studied isotopes on CNMs allow us to not only choose the conditions for their effective use in nuclear medicine, but also evaluate the sorption behavior of other nuclear medicine isotopes.