Synthesis of poly(vinyl alcohol)/C60 and poly(N-vinylpyrrolidone)/C60 nanohybrids as potential photodynamic cancer therapy agents

Well-defined poly(vinyl acetate) (PVAc) and poly(N-vinylpyrrolidone)-co-poly(vinyl acetate) (PNVPco-PVAc) chains end-capped by Co-(acac)2 (acac=acetylacetonate) and prepared by cobalt-mediated radical polymerization (CMRP) are grafted onto a fullerene. Homolytic Co-C bond cleavage of the polymer chain ends at 30°C releases the polymeric radicals that add onto C60, thereby leading to the corresponding PVAc/C60 and PNVP-co-PVAc/C60 nanohybrids. The [polymer–Co(acac)2]/[C60] molar ratio was varied to adjust the structure of the nanohybrids, and more particularly the number of grafted arms. Finally, the potential of the hydrosoluble PVOH/C60 nanohybrids, which result from the methanolysis of the ester groups of PVAc/C60, and of the PNVP-co-PVAc/C60 nanohybrids as photosensitizers for photodynamic therapy (PDT), was approached. First, photobleaching tests demonstrated the ability of these nanohybrids to produce singlet oxygen upon irradiation, which can play a role in cell damage. Second, cell viability assays demonstrated that both types of nanohybrids are deprived of intrinsic cytotoxicity in the dark, whereas they promoted significant cell mortality when subjected to light treatment. The selective response of these materials to irradiation makes them promising compounds for PDT.