Enhanced radical scavenging activity by antioxidant-functionalized gold nanoparticles: A novel inspiration for development of new artificial antioxidants

Because of its potent antioxidant function and important role in clinical treatment, a-tocopherol (vitamin E) is a good starting point in the development of new synthetic antioxidants with improved properties. In this paper the first example of antioxidant- functionalized gold nanoparticles, Au@Trolox, was synthesized by self-assembly of thiol ligands derived from Trolox, a vitamin E analogue, on gold nanoparticles. DPPH center dot (2,2-diphenyl-1-picrylhydrazyl) radical scavenging experiments revealed that the rate constant for the reaction of Au@Trolox with DPPH center dot was about eight times greater than that for Trolox. The product analysis showed that both the quinonoid and the diepoxide forms were possible oxidized products of the chromanol group of Au@Trolox treated with DPPH center dot radical. No remarkable influence was found on the antioxidant activity of Au@Trolox when the coverage rate of the antioxidant group on the surface of the gold was varied. All our results proved that the assembly of chromanol groups on gold nanoparticles could efficiently enhance the activity of the vitamin E-derived antioxidant, which presents a potential new strategy for antioxidant design with novel perspectives in potential applications. (C) 2007 Elsevier Inc. All rights reserved.