Atmospheric pressure generation of singlet oxygen by arrays of microplasmas for DNA oxidation

Recently, we demonstrated [1] that Micro-Cathode Sustained Discharges (MCSD) can be very effective for producing large amounts of O$_{2}$(a$^{1}\Delta )$ at atmospheric pressure. In the present work, we show that O$_{2}$(a$^{1}\Delta )$ densities higher than 3 10$^{16}$ cm$^{-3}$ can be produced by arrays of MCSD operating at atmospheric pressure in He/O$_{2}$/NO mixtures, resulting in O$_{2}$(a$^{1}\Delta )$ fluxes above 30 mmol/h. The effect of different parameters such as gas flows and mixtures, discharge current and array geometry are discussed. Arrays of MCSD, allowing the production at atmospheric pressure of O$_{2}$(a$^{1}\Delta )$ and O$_{3}$ densities between 10$^{13}$ and 10$^{16}$ cm$^{-3}$, with an easily tunable ratio, appear to be very useful tools to study in details the reactivity of these reactive oxygen species with DNA constituents. Experiments were conducted showing that Adenine, Thymine and Cytosine constituents are effectively oxidized by O$_{3}$, while O$_{2}$(a$^{1}\Delta )$ only reacts with 2'-deoxyguanosine (dGuo). A more detailed study on the reactivity of O$_{2}$(a$^{1}\Delta )$ and O$_{3}$ with aqueous DNA solutions is in progress. [1] J.S. Sousa et al., Appl. Phys. Lett. \textbf{93}, 011502 (2008)