Journal
SMALL
Volume 7, Issue 19, Pages 2775-2785Publisher
WILEY-V C H VERLAG GMBH
DOI: 10.1002/smll.201100651
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Funding
- NIH at the University of Rochester [RC2 ES018741]
- NIEHS [P42 ES013660, ES016178]
- Brown Office of the Vice President for Research
- Oak Ridge National Laboratory
- U.S. Department of Energy, Basic Energy Sciences, Materials Sciences and Engineering Division
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This article reports a direct chemical pathway for antioxidant deactivation on the surfaces of carbon nanomaterials. In the absence of cells, carbon nanotubes are shown to deplete the key physiological antioxidant glutathione (GSH) in a reaction involving dissolved dioxygen that yields the oxidized dimer, GSSG, as the primary product. In both chemical and electrochemical experiments, oxygen is only consumed at a significant steady-state rate in the presence of both nanotubes and GSH. GSH deactivation occurs for single-and multi-walled nanotubes, graphene oxide, nanohorns, and carbon black at varying rates that are characteristic of the material. The GSH depletion rates can be partially unified by surface area normalization, are accelerated by nitrogen doping, and suppressed by defect annealing or addition of proteins or surfactants. It is proposed that dioxygen reacts with active sites on graphenic carbon surfaces to produce surface-bound oxygen intermediates that react heterogeneously with glutathione to restore the carbon surface and complete a catalytic cycle. The direct catalytic reaction between nanomaterial surfaces and antioxidants may contribute to oxidative stress pathways in nanotoxicity, and the dependence on surface area and structural defects suggest strategies for safe material design.
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