ИСТИНА

The electrochemical behavior of new organic lipophilic PtIV complexes, namely, cis-[bis-nitroxyethyl isonicotinamide-N]tetrachloride platinum(IV) (1) and e-amine-d-(4-amino-2,2,6,6-tetramethylpiperidine-1-oxyl)-a,f-bis(octanoato)-b,c-dichloroplatinum(IV) (2) were investigated in DMSO and MeCN solutions on Pt, Au and glassy carbon electrodes by cyclic (CVA) and square-wave voltammetry (SWVA). The results were compared with those for a model system, namely, wide-spread drug cisplatin. The water-soluble hybrid materials of compounds 1 and 2 were prepared via solubilization of these PtIV complexes by copolymer nanoparticles of N-vinylpyrrolidone with (di)methacrylates [1-3]. They were characterized by dynamic light scattering (DLS), TEM, UV-Vis, and IR-spectroscopy. According to TEM and DLS, the hybrid materials consist of spherical particles with a hydrodynamic radius mainly ~(50–60) nm. The water-soluble hybrid forms of these Pt(IV) complexes were studied in aqueous phosphate buffer solutions (PBS) by electrochemical methods. The results were compared with those for their free and hybrid forms in DMSO and MeCN, and found to be quite different. CVA and SWVA curves of the water-soluble polymer particles loaded by compounds 1 and 2 and free Pt(IV) complexes in DMSO contain 3 to 5 irreversible cathodic peaks until E ~ -(1.5-2.5) V, resp. In contrast, only two overlapped peaks were observed for 1 within the potential region in PBS during a sufficiently long time. The free radical moiety of 2 exhibited one-electron irreversible cathodic and one-electron reversible anodic peaks in MeCN, and their potentials were substantially similar to those for long-lived 4-acetylamino-2,2,6,6-tetramethylpiperidine 1-oxyl radical (3). This free radical moiety kept its redox characteristics at the same level as 3. Electrochemical and non-electrochemical data testified in favor of the inclusion of Pt(IV) complexes in polymer particles that were quite stable in the aqueous medium during a sufficiently long time but subjected to destruction in non-aqueous solvents under study.