The Ability of Functionalized Fullerenes and Surface‐Modified TiO₂ Nanoparticles to Photosensitize Peroxidation of Lipids in Selected Model Systems

Abstract

Abstract Photochemical properties of a new class of inorganic nanoparticles, namely a cationic C 60 fullerene substituted with three quaternary pyrrolidinium groups ( BB 6) and a surface‐modified nanocrystalline TiO 2 with bromopyrogallol red (Brp@TiO 2 ) were examined for their effectiveness in photogenerating singlet oxygen and free radicals. In particular, their ability to photosensitize peroxidation of unsaturated lipids was analyzed in POPC :cholesterol liposomes and B16 mouse melanoma cells employing a range of spectroscopic and analytical methods. Because melanoma cells typically are pigmented, we examined the effect of melanin on the photosensitized peroxidation of lipids in liposomes and B16 melanoma cells, mediated by BB 6 and Brp@TiO 2 nanoparticles. The obtained results suggest that peroxidation of unsaturated lipids, photosensitized by BB 6 occurs mainly, although not exclusively, via Type II mechanism involving singlet oxygen. On the other hand, if surface‐modified TiO 2 is used as a photosensitizer, Type I mechanism of lipid peroxidation dominates, as indicated by the predominant formation of the free radical‐dependent cholesterol oxidation products. The protective effect of melanin was particularly evident when BB 6 was used as a photosensitizer, suggesting that melanin could efficiently interfere with Type II processes.