title: A new mechanism for hydroxyl radical production in irradiated nanoparticle solutions.
abstract: The absolute yield of hydroxyl radicals per unit of deposited X-ray energy is determined for the first time for irradiated aqueous solutions containing metal nanoparticles based on a "reference" protocol. Measurements are made as a function of dose rate and nanoparticle concentration. Possible mechanisms for hydroxyl radical production are considered in turn: energy deposition in the nanoparticles followed by its transport into the surrounding environment is unable to account for observed yield whereas energy deposition in the water followed by a catalytic-like reaction at the water-nanoparticle interface can account for the total yield and its dependence on dose rate and nanoparticle concentration. This finding is important because current models used to account for nanoparticle enhancement to radiobiological damage only consider the primary interaction with the nanoparticle, not with the surrounding media. Nothing about the new mechanism appears to be specific to gold, the main requirements being the formation of a structured water layer in the vicinity of the nanoparticle possibly through the interaction of its charge and the water dipoles. The massive hydroxyl radical production is relevant to a number of application fields, particularly nanomedicine since the hydroxyl radical is responsible for the majority of radiation-induced DNA damage.
authors.affiliation: Laboratoire de Chimie Physique CNRS UMR8000, Université Paris-Sud, 91405, Orsay Cedex, France.
authors.forename: Cécile
authors.initials: C
authors.lastname: Sicard-Roselli
authors.forename: Emilie
authors.initials: E
authors.lastname: Brun
authors.forename: Manon
authors.initials: M
authors.lastname: Gilles
authors.forename: Gérard
authors.initials: G
authors.lastname: Baldacchino
authors.forename: Colin
authors.initials: C
authors.lastname: Kelsey
authors.forename: Harold
authors.initials: H
authors.lastname: McQuaid
authors.forename: Chris
authors.initials: C
authors.lastname: Polin
authors.forename: Nathan
authors.initials: N
authors.lastname: Wardlow
authors.forename: Frederick
authors.initials: F
authors.lastname: Currell
mesh_terms: D017665:Hydroxyl Radical / Q000737:chemistry*; D046529:Microscopy, Electron, Transmission; D053758:Nanoparticles; D012996:Solutions; D014965:X-Rays
chemical_list: D012996:Solutions; D017665:Hydroxyl Radical
keywords: coumarin; gold nanoparticles; hydroxyl radicals; water-nanoparticle interfaces