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Chem Res Toxicol. 2008 May;21(5):1056-63. doi: 10.1021/tx800056w. Epub 2008 Apr 19.

Pristine (C60) and hydroxylated [C60(OH)24] fullerene phototoxicity towards HaCaT keratinocytes: type I vs type II mechanisms.

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  • 1Laboratory of Pharmacology and Chemistry, National Institute of Environmental Health Sciences, Research Triangle Park, North Carolina 27709, USA.


The increasing use of fullerene nanomaterials has prompted widespread concern over their biological effects. Herein, we have studied the phototoxicity of gamma-cyclodextrin bicapped pristine C 60 [(gamma-CyD) 2/C 60] and its water-soluble derivative C 60(OH) 24 toward human keratinocytes. Our results demonstrated that irradiation of (gamma-CyD) 2/C 60 or C 60(OH) 24 in D 2O generated singlet oxygen with quantum yields of 0.76 and 0.08, respectively. Irradiation (>400 nm) of C 60(OH) 24 generated superoxide as detected by the EPR spin trapping technique; superoxide generation was enhanced by addition of the electron donor nicotinamide adenine dinucleotide (reduced) (NADH). During the irradiation of (gamma-CyD) 2/C 60, superoxide was generated only in the presence of NADH. Cell viability measurements demonstrated that (gamma-CyD) 2/C 60 was about 60 times more phototoxic to human keratinocytes than C 60(OH) 24. UVA irradiation of human keratinocytes in the presence of (gamma-CyD) 2/C 60 resulted in a significant rise in intracellular protein-derived peroxides, suggesting a type II mechanism for phototoxicity. UVA irradiation of human keratinocytes in the presence of C 60(OH) 24 produced diffuse intracellular fluorescence when the hydrogen peroxide probe Peroxyfluor-1 was present, suggesting a type I mechanism. Our results clearly show that the phototoxicity induced by (gamma-CyD) 2/C 60 is mainly mediated by singlet oxygen with a minor contribution from superoxide, while C 60(OH) 24 phototoxicity is mainly due to superoxide.

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