Biomedical potential of the reactive oxygen species generation and quenching by fullerenes (C60)

Fullerene (C-60), a third carbon allotrope, is a classical engineered material with the potential application in biomedicine. One of the biologically most relevant features of C-60 is the ability to quench various free radicals, behaving as a free radical sponge. Conversely, photosensitization of C-60 leads to its transition to a long-lived triplet excited state and the subsequent energy or electron transfer to molecular oxygen, yielding highly reactive singlet oxygen (O-1(2)) or superoxide anion (O-2(center dot-)), respectively. These reactive oxygen species (ROS) react with a wide range of biological targets and are known to be involved in both cellular signaling and cell damage. Therefore, the dual property of fullerenes to either quench or generate cell-damaging ROS could be potentially exploited for their development as cytoprotective or cytotoxic anticancer/antimicrobial agents. However, the attempts to that effect have been hampered by the extremely low water solubility of C-60, and by the fact that solubilization procedures profoundly influence the ROS-generating/quenching properties of C-60, either through chemical modification or through formation of complex nanoscale particles with different photophysical properties. We here analyze the mechanisms and biological consequences of ROS generation/quenching by C-60, focusing on the influence that different physico-chemical alterations exert on its ROS-related biological behavior. (c) 2008 Elsevier Ltd. All rights reserved.