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

Abstract

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.

Controlling plasma‐activated solution chemistry for targeted cancer cell death

“…Figure 6b shows that the intensity of the N 2 second positive system emission spectrum increases and then decreases, a phenomenon like that of the He discharge. [ 41 ] The spectral peaks of N 2 (C‐B) were the maximum in the PB group and the minimum in the DI group. Figure 6c represents the peak of the Ar (696 nm) spectral line, where the formation of the Ar‐excited state is mainly due to direct electron impact on the ground state.…”

Investigation of the chemical characteristics and anticancer effect of plasma‐activated water: The effect of liquid temperature

“…where ε is the molar absorptivity of the chemical species at a certain wavelength λ, l is the optical path length, and c presents the concentration of RONS. [29,30] For the evaluation of the total RONS concentration, total absorbance was calculated to reflect the RONS concentration. [29,30] The calculated equation of the total absorbance was defined by the following equation [29] :…”

“…[29,30] For the evaluation of the total RONS concentration, total absorbance was calculated to reflect the RONS concentration. [29,30] The calculated equation of the total absorbance was defined by the following equation [29] :…”

“…[33] The pH value can reflect the concentration of H + in the PAW, and the ionization of nitrites and nitrates are the main source of H + . [10] Nitrites and nitrates are generated by the dissolution of NO x , originating from the reactions of N 2 and O 2 in the gas phase during discharge,[ 10,29] but the dissolution of NO x into water decreases as the water temperature increases. [34] That is why the pH value increases as the temperature changes from 25°C to 40°C and 70°C.…”

“…According to the previous reports, ONOO − is a key chemical species generated in PAW. [1,29] ONOO − is capable of oxidizing, nitrating, and hydroxylating biomolecules under physiological conditions, leading to cytotoxicity. [1] Although O 2 − gets a high reactive activity, the O 2 − has a short lifetime and may not be able to exert a great influence on apoptosis.…”