Investigation of optimum discharge characteristics and chemical activity of AC driven air plasma jet and its anticancer effect

In this study, we investigated the effects of the quartz tube diameter, air flow rate, and applied voltage on the characteristics of an air plasma jet to obtain the optimized discharge characteristics. The physicochemical properties and concentration of reactive oxygen and nitrogen species (RONS) in plasma-activated medium (PAM) were characterized to explore their chemical activity. Furthermore, we investigated the inactivation effect of air plasma jet on tumour cells and their corresponding inactivation mechanism. The results show that the tube diameter plays an important role in sustaining the voltage of the air plasma jet, and the gas flow rate affects the jet length and discharge intensity. Additionally, the air plasma jet discharge displays two modes, namely, ozone and nitrogen oxide modes at high and low gas flow rates, respectively. Increasing the voltage increases the concentration of reactive species and the length of discharge. By evaluating the viability of A549 cells under different parameters, the optimal treatment conditions were determined to be a quartz tube diameter of 4 mm, gas flow rate of 0.5 SLM, and voltage of 18 kV. Furthermore, an air plasma jet under the optimized conditions effectively enhanced the chemical activity in PAM and produced more aqueous RONS. The air plasma jet induced significant cytotoxicity in A549 cancer cells after plasma treatment. H2O2 and \rmNO_2^- are regarded as key factors in promoting cell inactivation. The present study demonstrates the potential use of tumour cell therapy by atmospheric air PAM, which aids a better understanding of plasma liquid chemistry.