Discharge characteristics of a microsecond pulse power supply driven air plasma jet and its anticancer cell effect

Abstract

In plasma cancer therapy, atmospheric pressure plasma jets have attracted increasing attention in recent years. In this study, from the point of view of economic costs and portability, we have employed atmospheric air as the working gas in order to investigate the effects of the rate of flow, applied voltage, frequency, and pulse width on the characteristics of discharge. The concentrations of reactive oxygen and nitrogen species (RONS) in a plasma-activated medium (PAM) were characterized in order to explore their chemical activity. In addition, the inactivating effect of tumor cells induced by an air plasma jet was investigated and the corresponding inactivation mechanism is also discussed. The results showed that the discharge intensity was positively correlated with frequency and voltage, and negatively correlated with pulse width. Regarding the gas flow rate, when the air flow rate was 1 standard liter per minute (SLM), the discharge intensity was strongest according to the length of the plume. By summarizing the discharge characteristics and emission spectra under different experimental parameters, the stable treatment conditions producing rich active substances were as follows: a frequency of 6 kHz, a voltage of 14 kV, a gas flow rate of 1 SLM, and a pulse width of 1 μs. Furthermore, under these stabilized conditions, the air plasma jet produced rich aqueous RONS in a PAM effectively, which killed cells in significant numbers and reduced the cell survival rate. Therefore, this study demonstrates the potential application of an atmospheric PAM for the treatment of tumor cells and promotes a deeper understanding of plasma liquid chemistry.