Gas Flow-Dependent Modification of Plasma Chemistry in mu APP Jet-Generated Cold Atmospheric Plasma and Its Impact on Human Skin Fibroblasts

The micro-scaled Atmospheric Pressure Plasma Jet (mu APPJ) is operated with low carrier gas flows (0.25-1.4 slm), preventing excessive dehydration and osmotic effects in the exposed area. A higher yield of reactive oxygen or nitrogen species (ROS or RNS) in the mu AAPJ-generated plasmas (CAP) was achieved, due to atmospheric impurities in the working gas. With CAPs generated at different gas flows, we characterized their impact on physical/chemical changes of buffers and on biological parameters of human skin fibroblasts (hsFB). CAP treatments of buffer at 0.25 slm led to increased concentrations of nitrate (similar to 352 mu M), hydrogen peroxide (H2O2; similar to 124 mu M) and nitrite (similar to 161 mu M). With 1.40 slm, significantly lower concentrations of nitrate (similar to 10 mu M) and nitrite (similar to 44 mu M) but a strongly increased H2O2 concentration (similar to 1265 mu M) was achieved. CAP-induced toxicity of hsFB cultures correlated with the accumulated H2O2 concentrations (20% at 0.25 slm vs. similar to 49% at 1.40 slm). Adverse biological consequences of CAP exposure could be reversed by exogenously applied catalase. Due to the possibility of being able to influence the plasma chemistry solely by modulating the gas flow, the therapeutic use of the mu APPJ represents an interesting option for clinical use.