Microplasma Generation of Reactive Oxygen Species for DNA Oxidation

We have developed arrays of microcathode sustained discharges (MCSD) for the generation of singlet delta oxygen (SDO) at atmospheric pressure. In He/O$_{2}$/NO mixtures, SDO densities higher than 1.0 10$^{17}$cm$^{-3}$ have been efficiently produced and transported over distances longer than 50cm, providing SDO fluxes greater than 100mmol/h. Additionally, ozone (O$_{3})$ densities up to 10$^{16}$cm$^{-3}$ have also been obtained. As the ratio between SDO and O$_{3}$ can be easily and finely tuned in the range 10$^{-3}$-10$^{+3}$, these arrays of MCSD are very useful tools for examining the reactivity of these reactive oxygen species (ROS) with biological components. Experiments were performed showing that SDO and O$_{3}$ are able to oxidize DNA. We observed that O$_{3}$ is much more efficient than SDO at degrading DNA. While O$_{3}$ oxidizes all DNA nucleobases almost indifferently, SDO reacts mainly with Guanine. We also report that 4-OH-8-oxodGuo is produced by the SDO oxidation of dGuo, and can, thus, be used as a SDO biomarker. A more detailed study on the reactivity of ROS with DNA is currently in progress.