Fullerene (C60) undergoes various transformations in the environment, resulting in toxicity modification. This study confirmed that C60 aggregate (nC60) was transformed to more oxidized form under commonly used water disinfection process (i.e., UV and UV/chlorine treatment). nC60 under UV irradiation showed less cytotoxicity to macrophage J774 in comparison with parent nC60, which thanked to its decreased hydrophobicity and oxidative potential. However, obvious increased cytotoxicity was observed after UV/chlorine treatment (photochlorinated_ nC60), sharp contrary to its also oxidized and hydrophilic form. The intrinsic mechanism could be attributed to its superoxide dismutase activity, resulting in efficient conversion of extracellular superoxide anion (O2.-) to highly oxidative hydrogen peroxide. Under this oxidative stress, more nanoparticles entered into cell, resulting in serious DNA damage and cell death. The presences of electron withdrawing groups (i.e., chlorine and carbonyl) on photochlorinated_nC60 facilitated the attack of O2.- to electron deficient conjugated π systems of C60. Moreover, photochlorinated_ nC60 acted as electron mediator to expedite electron transfer from cell to extracellular oxygen, leading to more O2.- formation. The structure-related electron mediating effect was confirmed through evident correlations between carbonyl content on C60 cage and its electron transfer activity and change of cell membrane potential upon interaction. Our results highlight the importance of understanding environmental transformation induced toxicity alteration, which are likely to differ significantly from parent material properties and behaviors.

Photochlorinated fullerene increase cytotoxicity towards macrophage J774 via acting as SOD and electron-transfer mediator

255th National Meeting (2018)

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