Kinetic analysis of superoxide anion radical-scavenging and hydroxyl radical-scavenging activities of platinum nanoparticles.
There are few reports on the physiological effects of metal nanoparticles (nps), especially with respect to their functions as scavengers for superoxide anion radical (O2(.-)) and hydroxyl radical (.OH). We tried to detect the scavenging activity of Pt nps using a hypoxanthine-xanthine oxidase system for O2(.-) and using a Fenton and a UV/H2O2 system for .OH. Electron spin resonance analysis revealed that 2 nm particle size Pt nps have the ability to scavenge O2(.-) and .OH. The calculated rate constant for the O2(.-)-scavenging reaction was 5.03 +/- 0.03 x 10(7) M (-1) s (-1). However, the analysis of the Fenton and UV/H 2O 2 system in the presence of Pt nps suggested that the .OH-scavenging reaction cannot be determined in both systems. Among particle sizes tested from 1 to 5 nm, 1 nm Pt nps showed the highest O2(.-)-scavenging ability. Almost no cytotoxicity was observed even after adherent cells (TIG-1, HeLa, HepG2, WI-38, and MRC-5) were exposed to Pt nps at concentrations as high as 50 mg/L. Pt nps scavenged intrinsically generated reactive oxygen species (ROS) in HeLa cells. Additionally, Pt nps significantly reduced the levels of intracellular O2(.-) generated by UVA irradiation and subsequently protected HeLa cells from ROS damage-induced cell death. These findings suggest that Pt nps may be a new type of antioxidant capable of circumventing the paradoxical effects of conventional antioxidants.
Department of Genetic Resources Technology, Faculty of Agriculture, Kyushu University, Hakozaki, Higashi-ku, Fukuoka 812-8581, Japan.
Takeki
T
Hamasaki
Taichi
T
Kashiwagi
Toshifumi
T
Imada
Noboru
N
Nakamichi
Shinsuke
S
Aramaki
Kazuko
K
Toh
Shinkatsu
S
Morisawa
Hisashi
H
Shimakoshi
Yoshio
Y
Hisaeda
Sanetaka
S
Shirahata
D000838:Anions / Q000737:chemistry; D002460:Cell Line; D002470:Cell Survival / Q000187:drug effects; D006801:Humans; D017665:Hydroxyl Radical / Q000737:chemistry*; D007700:Kinetics; D053768:Metal Nanoparticles / Q000737:chemistry* / Q000633:toxicity / Q000648:ultrastructure; D008854:Microscopy, Electron; D010316:Particle Size; D010984:Platinum / Q000737:chemistry* / Q000633:toxicity; D013481:Superoxides / Q000737:chemistry*
D000838:Anions; D013481:Superoxides; D017665:Hydroxyl Radical; D010984:Platinum