The impact of surface-to-volume ratio on the plasma activated water characteristics and its anticancer effect

Plasma activated water (PAW), as a green and potential technology, plays a significant role in bio-medicine applications. Surface-to-volume ratio of treated liquid during the preparation of PAW seriously affects the PAW chemistry characteristics, and ultimately results in different biological effects. However, that how does the surface-to-volume ratio affect PAW characteristics and anticancer effect induced by PAW is unclear. In this work, the surface-to-volume ratio is regulated to investigate the dynamic variation of chemical characteristics and cell apoptosis. Results display physicochemical properties including pH, ORP, and liquid temperature are varied with nonlinear trend besides conductivity. While the levels of RONS containing NO2-, NO3-, H+ are changed with linear trend except H2O2 ONOO- and O .2-. Furthermore, increasing surface-to-volume ratio could effectively accelerate cell apoptosis, enhance intracellular ROS concentration and strengthen anticancer effects. Thus, it is concluded that tuning surface to volume ratio can effectively enhance the reactive species flux into the liquid that leads to remarkable anticancer activity of PAW rather than the surface-to-volume ratio that is directly responsible for the enhanced impact on the cells. Additionally, the possible apoptosis mechanisms linked with RONS are also discussed. Clarifying the relationship between the surface-to-volume ratio and the PAW characteristics is beneficial to much insights into the chemistry nature of PAW and tailoring biological effect caused by PAW.