Safety and anticancer effects of slit-opposed plasma sources

Atmospheric pressure plasma technology has demonstrated promising anticancer effects in cancer therapy. However, its limited effective treatment area fails to meet the demands of larger treatment zones. In this study, a size-broadened plasma plume was generated using a slitopposed-electrode structure. The discharge characteristics, liquid-phase reactive species, anticancer cell effect, and optimization of discharge performance through a four-electrode configuration were systematically investigated. The results indicate that increasing the gas flow rate can extend the longitudinal plasma plume by lengthening the downward movement of microdischarge filaments. However, beyond 6 SLM, the plume length remained essentially unchanged. Raising the discharge voltage significantly enhanced discharge intensity, exerting a greater influence on discharge characteristics than gas flow rate adjustments. But excessive gas flow and voltage levels led to non-uniform filament stacking. Regarding anticancer cell effect, the concentrations of H₂O₂, NO₂⁻, and ONOO⁻/O₂⁻ increased with plasma treatment time. After 4 min of treatment, the two-electrode and four-electrode slit devices inactivated 70% and 80% of A549 tumor cells, respectively. Finally, through the optimization of the four-electrode structure, it was found that incorporating an upper-level discharge helped improve the stability and uniformity of the downstream discharge under high voltage, thereby enhancing the discharge characteristics of the device. This study demonstrates the potential application of slit-opposed-electrode plasma jets for cancer treatment and promotes a better understanding of the mechanism and efficient operation of slit plasma jets.