Inactivation of nanocrystalline C60 cytotoxicity by gamma-irradiation.

We investigated the effect of gamma-irradiation on the cytotoxicity of pure C60 solubilized in water by using tetrahydrofuran (THF/n-C60 or THF/n-C60). In contrast to THF/n-C60, its gamma-irradiated counterpart failed to generate oxygen radicals and cause extracellular signal-regulated kinase (ERK)-dependent necrotic cell death in various types of mammalian cells. Moreover, gamma-irradiated THF/n-C60 protected cells from the oxidative stress induced by native THF/n-C60 or hydrogen peroxide. The observed biological effects were associated with gamma-irradiation-mediated decomposition of THF and subsequent derivatization of the n-C60 surface. These results for the first time demonstrate gamma-irradiation-mediated changes in the physico-chemical properties of THF-prepared nanocrystalline C60, resulting in a complete loss of its cytotoxic effect and its conversion to a cytoprotective agent.