Insight into hollow electrode plasma jet array for tumor cell apoptosis via different O₂ concentrations

Hollow electrode discharge is commonly utilized across various fields, but the research on hollow electrode discharge plasma jet array and its corresponding anticancer effect remains limited, especially their induced liquid chemistry and biological effects. This study describes the generation of plasma multi-jet through a novel-designed hollow electrode array generator and the anticancer effect of plasma-activated water (PAW) through multi-jet treatment. The rise of O₂ concentration has affected the discharge morphology, electrical characteristics, and gaseous reactive species generation, resulting in differences in the liquid-phase chemical properties of PAW. Among these, the N₂-related gaseous emissive species decrease with the rise of the O₂ ratio, while the O-related species show a first increasing and then decreasing trend. Furthermore, the PAW produced under 0% of O₂ contains more ONOO⁻ and O₂⁻ species, while the PAW generated under 0.3% O₂ contains more H₂O₂ and NO₂⁻ species. On this basis, the PAW generated at a relatively low O₂ percentage (0% and 0.3%) results in a higher inactivation efficiency against cancer cells due to the high concentrated H₂O₂, NO₂⁻, and ONOO⁻/O₂⁻. This study offers insights into the design of plasma generation devices and the preparation of PAW for practical tumor therapy.