Differences in Cytotoxicity Induced by Cold Atmospheric Plasma and Exogenous RONS Solutions on Human Keratinocytes and Melanoma Cells

Cancer treatment is a promising clinical application of cold atmospheric plasma due to its selectivity in killing cancer cells. Whether there are differences in selectively killing of canners among direct plasma treatment, plasma-activated media (PAM), and exogenous reactive oxygen and nitrogen species (RONS) solutions made by chemical methods is an important issue that needs to be addressed. In this study, human keratinocytes (HaCaT cells) and melanoma cells (A875) were chosen as in vitro models to compare the biological effects of direct plasma treatment, PAM, and exogenous long-lived RONS solutions on human nonmalignant and cancer cells. Cell viability assay and intracellular ROS measurement were performed on HaCaT cells and A875 cells after treatment. The concentrations of long-lived species in PAM were measured. It was found that PAM and exogenous RONS solutions exhibited more toxicity on normal HaCaT cells than A875 cells while direct plasma treatment can selectively kill A875 cells when the treatment time was well controlled. These results indicated that PAM treatment seems to have no obvious differences in terms of its selectivity in killing A875 cells compared to the exogenous RONS solutions. The biological effects of direct plasma treatment and PAM treatment are not similar in all cases.