25 - EPR Based Estimation of Radiation-Induced Reactive Oxygen Species

Abstract

Generation of reactive oxygen species (ROS) is considered as essential trigger of biological effects of ionizing radiations, and may be deeply linked with the radiation quality. Amounts of total oxidation reactions (i.e. oxidative free radical species, ● OH and HO 2●– ), H 2 O 2 generations, Oxygen consumptions, and • OH generations induced by X-ray, 20 keV/μm carbon beam, and 80 keV/μm carbon beam were estimated using EPR based techniques. Total oxidation reactions were estimated as 3, 1.3, and 0.66 μmol/L/Gy, amount of H 2 O 2 generations were 0.2, 0.57, and 0.35 μmol/L/Gy, oxygen consumptions were 0.4, 0.39, and 0.15 μmol/L/Gy for X-ray, 20 keV/μm carbon beam, and 80 keV/μm carbon beam, respectively. The ratio of H 2 O 2 generation per oxygen consumption were increased with LET, and were 0.5, 1.46, 2.33 for X-ray, 20 keV/μm carbon beam, and 80 keV/μm carbon beam, respectively. The ● OH generations expected to be localized on the track/range of the radiation beam/ray, and both sparse (≈ 3.3 mM) and very dense (> 1.7 M) ● OH generations were suggested. Percentage of sparse ● OH generation decreased with LET becoming higher.