Cold atmospheric plasma cancer treatment, direct versus indirect approaches

Cold atmospheric plasma (CAP), an ionized gas with near room temperature, shows a wide application in medicine. CAP is a tunable source of complex chemical components including many reactive species, which allows CAP to exert many biological effects on bacterial, fungal, yeast, and mammalian cells particularly cancer cells. In this review, we discuss the novel state of the art CAP-based cancer treatment. We focus on the comparison between the direct CAP treatment and the indirect CAP treatment which implements the use of CAP-activated solutions such as medium. The difference between the two treatment strategies reveals two unique features of the biological response to CAP: the cell-based H2O2 generation and the activation phenomenon on cancer cells. Short-lived reactive species and electromagnetic emission from plasma may be the cause of these two cellular responses.