Biological and chemical effects of water activated by cold plasma above and beneath the water surface

Summary form only given. In this study, we compared the disinfection abilities of A-PAW and B-PAW generated by cold plasma above (A-PAW) and beneath (B-PAW) the water surface. Then various techniques were applied to assess the differences of A-PAW and B-PAW from the characteristics of PAW solutions and biological standpoint. Staphylococcus aureus (S.aureus) was used as a model bacterium to verify inactivation efficacy of A-PAW and B-PAW. For estimating characteristics of PAW solutions, physical, electrochemical, and biochemical methods were involved. Optical emission spectroscopy (OES) was employed to detect the reactive species in PAW. The pH value and temperature of PAW were recorded during the experiments. The electric conductivity and oxidation reduction potential (ORP) of PAW were monitored by different standard electrodes respectively. In addition, the hydrogen peroxide contents of PAW were quantified by Hydrogen Peroxide Assay Kit. The biological effects of PAW were analyzed by measuring the membrane potential of S.aureus through a potential-sensitive probe (carbocyanine dye DiOC₂(3)) via flow cytometry. The integrity of the cell membranes were investigated by determining release of cellular DNA and protein absorbed at 260 nm and 280 nm. Moreover, intracellular reactive oxygen species (ROS) is measured with the probe 2´,7´dichlorofluorescein diacetate (DCFH-DA) by fluorescence microscopy.