The liquid temperature during the preparation of plasma-activated water (PAW) seriously affects the PAW chemical characteristics and its biological effect. In this study, four different temperatures (4°C, 25°C, 40°C, and 70°C) of deionized water are selected as variable parameters to investigate the effect on PAW. The results show that the physicochemical properties and the concentration of reactive oxygen and nitrogen species of PAW are significantly reduced when the temperatures are higher than 25°C; moreover, the above indexes are slightly decreased
Surface air discharge has been extensively reported to have strong antibacterial and anticancer effects, and these biological effects are more or less attributed to the short-lived aqueous reactive species produced by the air plasma. Insight into the generation mechanism for short-lived species is a key bottleneck in elucidating the antimicrobial and anticancer effects. Although the numerical study has predicted that the dissolution of gaseous NO3 plays a crucial role, but so far without experimental validation. In view of this, cavity ring-down spectroscopy is adopted in this paper to measure the NO3 spatial distribution between the surface air discharge and the solutions to be treated, and the concentrations of short-lived species in the solutions after plasma treatment are also measured for different discharge modes. A simplified chemical pathway for the conversion of gaseous NO3 to aqueous ONOOaq −/ONOOHaq and O2aq − is proposed. Moreover, the inactivation effects for Escherichia coli and A549 lung cancer cells treated by the plasma-activated solutions are measured for different concentrations of short-lived species, and the key species for sterilization and anticancer are identified by chemical scavengers. Finally, a positive correlation chain is found among the inactivation effect, the concentrations of aqueous ONOOaq −/ONOOHaq and O2aq −, and the density of gaseous NO3, implying that NO3 might be very important for the production of aqueous short-lived reactive species as well as the biological effects induced by plasma-activated solutions.
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.
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. H 2 O 2 and -NO 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.
Plasma-activated solution (PAS) has attracted wide attention in cancer treatment because it can treat deep tumors and offer storability. The changes in reactive species and physicochemical properties of PAS during storage can affect its anticancer effect. In this study, the plasma-activated medium (PAM) was prepared by treating RPMI 1640 medium with afterglow gas generated by a custom-built air surface dielectric barrier discharge device. PAM was stored at four common temperature conditions (25 °C, 4 °C, −20 °C, and −80 °C) for 1 day, 4 days, and 7 days, and then, the physicochemical properties, reactive oxygen and nitrogen species (RONS), and the anti-cancer effect on A549 cells under different storage conditions were compared. The results showed that PAM exhibited different anticancer effects at different storage temperatures over a 7 day storage period. The anticancer ability of PAM under 80 °C storage remained stable after 7 days of storage and decreased at all other temperatures. These results were also verified by apoptosis results, and the differences were mainly related to the concentration of H2O2 and NO2−, and oxido reduction potential. Our results provided a theoretical basis for the storage of PAM and its application in anticancer therapy.
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