title: Generation of reactive oxygen species induced by gold nanoparticles under x-ray and UV Irradiations.
abstract: The radiosensitizing effect of 5-250 nm diameter Au nanoparticles (AuNPs) in water was investigated under irradiations of diagnostic x-ray and UV light. Enhanced generations of hydroxyl radical ((·)OH) and superoxide anion (O(2)(-)) were confirmed from their dependencies on the absorbed energy, ethanol concentration and AuNPs' concentration. Two kinds of fluorescent probes revealed that the reactive oxygen species (ROS) generation rate under x-ray irradiation was enhanced by factors of 1.46 for (·)OH and 7.68 for O(2)(-). Photo- and Auger electron charge transfer is possibly relevant to generation of O(2)(-) near the particle surface, whereas fluorescent x-rays are involved in generation of (·)OH in the secondary water radiolysis. Smaller diameter AuNPs with larger surface area showed a greater yield of ROS. An inverse proportion of ROS generation to the AuNPs' diameter suggests a catalytic function of AuNPs' surface for enhanced ROS generation.
authors.affiliation: Institute for Human Science and Biomedical Engineering, National Institute of Advanced Industrial Science & Technology (AIST), Tsukuba, Ibaraki Japan. m.misawa@aist.go.jp
authors.forename: Masaki
authors.initials: M
authors.lastname: Misawa
authors.forename: Junko
authors.initials: J
authors.lastname: Takahashi
mesh_terms: D002384:Catalysis; D006046:Gold / Q000737:chemistry* / Q000494:pharmacology; D053768:Metal Nanoparticles / Q000737:chemistry*; D010316:Particle Size; D011838:Radiation-Sensitizing Agents / Q000494:pharmacology*; D017382:Reactive Oxygen Species / Q000378:metabolism*; D014466:Ultraviolet Rays; D014867:Water; D014965:X-Rays
chemical_list: D011838:Radiation-Sensitizing Agents; D017382:Reactive Oxygen Species; D014867:Water; D006046:Gold