Impact of synergism of nitrite and hydrogen peroxide on cell survivals in Plasma-Activated-Medium (PAM)

Summary form only given. Introduction Non-equilibrium atmospheric pressure plasma (NEAPP) applications for medicine are attracted attention in plasma irradiated cell culture medium, called as Plasma-Activated-Medium (PAM). Selectively killing effect of cancer cells without killing normally cells was reported for incubation with the PAM. Even though the effect can apply for cancer cure, the mechanism of antitumor effect has not been elucidated yet. The plasma generates short-lived reactive species such as Reactive Oxygen and Nitrogen Species (RONS). These disso lve into the medium and finally change to long-lived species such as H2O2 and NO2-. It was reported that H2O2 was regard ed as the antitumor factor of PAM. In this study, synergism o f NO2and H2O2 contributing the antitumor effect has been in vestigated. Experimental 3 mL of medium (DMEM) was set 13 m m under the NEAPP source. The PAM was made by 60 to 30 0 s of the NEAPP (7 kVp-p, 60 Hz, Ar 2 slm) irradiation. H2O2 and NO2concentration in the PAM was measured by u sing colorimetry. 10000 cells/well of U251SP (glioblastoma) cells were grown in PAM or medium containing the equivale nt concentrations of H2O2 and NO2-. After 24 h of incubation, the cell survival was measured by MTS assay. Results Concentrations of H2O2 and NO2generat ed in PAM were in proportion to plasma irradiation period wi th the rates of 0.35 μM/s and 9.8 μM/s. For incubation of U2 51SP cells, cell survival of medium added NO2remained unc hanged at 108.5±4.7%. In medium added H2O2, cell survivals were of 22.1±0.6%. Surprisingly, in medium added both H2O2 and NO2-, it decreased to lower 8.9±0.3% than that for the medium added only H2O2. At least, NO2enhances the ant itumor effect, compared with the effect of H2O2. The PAM ha s significant effective in the antitumor mechanism, cell surviv al of 1.6±0.4%. As the result, we believe that there can be un derstandable the other antitumor mechanism for the PAM.