title: In vitro free radical scavenging activity of platinum nanoparticles.
abstract: A polyacrylic acid (PAA)-protected platinum nanoparticle species (PAA-Pt) was prepared by alcohol reduction of hexachloroplatinate. The PAA-Pt nanoparticles were well dispersed and homogeneous in size with an average diameter of 2.0 +/- 0.4 nm (n = 200). We used electron spin resonance to quantify the residual peroxyl radical ([Formula: see text]) generated from 2,2-azobis (2-aminopropane) dihydrochloride (AAPH) by thermal decomposition in the presence of O(2) and a spectrophotometric method to quantify the residual 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical. PAA-Pt scavenged these two radicals in a dose-dependent manner. Platinum was the functional component. PAA-Pt reduced the rate of oxygen consumption required for linoleic acid peroxidation initiated by [Formula: see text] generated from AAPH, indicating inhibition of the propagation of linolate peroxidation. A thiobarbituric acid test also revealed dose-dependent inhibition of the linolate peroxidation by PAA-Pt. Fifty micromolar platinum, as PAA-Pt, completely quenched 250 microM DPPH radical for 5 min. Even when twice diluted in half, the PAA-Pt still quenched 100% of the 250 microM DPPH radical. The scavenging activity of PAA-Pt is durable. These observations suggest that PAA-Pt is an efficient scavenger of free radicals.
authors.affiliation: Department of Integrated Biosciences, Graduate School of Frontier Sciences, University of Tokyo, Bioscience Building 402, 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8562, Japan.
authors.forename: Aki
authors.initials: A
authors.lastname: Watanabe
authors.forename: Masashi
authors.initials: M
authors.lastname: Kajita
authors.forename: Juewon
authors.initials: J
authors.lastname: Kim
authors.forename: Atsuhiro
authors.initials: A
authors.lastname: Kanayama
authors.forename: Kyoko
authors.initials: K
authors.lastname: Takahashi
authors.forename: Tadahiko
authors.initials: T
authors.lastname: Mashino
authors.forename: Yusei
authors.initials: Y
authors.lastname: Miyamoto
mesh_terms: D000578:Amidines / Q000737:chemistry; D001713:Biphenyl Compounds / Q000737:chemistry; D016166:Free Radical Scavengers / Q000737:chemistry* / Q000494:pharmacology*; D019787:Linoleic Acid / Q000737:chemistry; D015227:Lipid Peroxidation / Q000187:drug effects; D053768:Metal Nanoparticles / Q000737:chemistry*; D010545:Peroxides / Q000737:chemistry; D010851:Picrates / Q000737:chemistry; D010984:Platinum / Q000737:chemistry*
chemical_list: D000578:Amidines; D001713:Biphenyl Compounds; D016166:Free Radical Scavengers; D010545:Peroxides; D010851:Picrates; C049375:perhydroxyl radical; D010984:Platinum; C046728:2,2'-azobis(2-amidinopropane); D019787:Linoleic Acid; C004931:1,1-diphenyl-2-picrylhydrazyl