Anticancer effects of DBD plasma-activated saline within different discharge modes

With a change in ambient temperature and discharge power, air discharge plasma can switch between two typical modes, namely the ozone mode and the NO (x) mode. Here, we analyze the physicochemical properties and anticancer effects of air dielectric barrier discharge (DBD) plasma-activated saline (PAS) treated by ozone-riched gas produced in an ozone discharge mode, NO (x) -riched gas produced in a NO (x) discharge mode, and a mixture of both produced in the combined two modes simultaneously. The results show that gaseous and aqueous reactive oxygen species (ROS) and reactive nitrogen species (RNS) generated by plasma vary in different discharge modes, correlating to the amount of high-valance nitroxides. In the ozone mode, ozone and minor N2O5 are generated in the gaseous phase and are transformed to aqueous ROS and RNS. In the NO (x) mode, low-valance RNS are generated in the gaseous phase but are transformed into less aqueous RNS. For the PAS produced by the mixed gases, not only the highest concentrated ROS are generated, but also the most abundant gaseous high-valence RNS are produced and transformed to aqueous RNS in the saline. In vitro experiments reveal that, although A375 cells incubated with these three PASs (30%) could all inhibit their viability by enhancing intracellular oxidative stress and inducing cell apoptosis, the PAS produced by the mixed gases has the strongest anticancer effects. Further studies suggest that high-valence RNS play a key role in PAS-induced anticancer effects.