Comparison of the physicochemical properties and inactivation against tumor cells of PAW induced by underwater single-hole and multi-hole bubble plasma

Plasma-activated water (PAW) regarded as a green alternative is of great interest in biomedicine due to the presence of a rich diversity of aqueous reactive oxygen and nitrogen species (RONS). Optimizing the reactor parameter is an important approach to regulate RONS in PAW to obtain better biological effects. This work mainly focuses on the number of micro holes of the plasma device to realize underwater bubble discharge. By comparing single-hole and multi-hole plasma under the same pulse voltage, the multi-hole plasma would produce a better discharge characteristic, and the prepared PAW presents superior physicochemical properties to realize high level RONS production by means of microbubbles to increase the contact area with water molecules. Furthermore, the A549 lung carcinoma cells are used to verify the inactivation effect induced by PAW treated by underwater single-hole and multi-hole bubble plasma, respectively, and the results show that the multi-hole plasma would induce cell apoptosis reaching up to 57.4%, while only 31.2% apoptosis efficiency for single-hole plasma. This mainly contributes to the high concentration of key species (NO2-, H2O2, ONOO-/O2-, and ·OH) produced by multi-hole plasma. This study is helpful to insight into the influence of underwater bubble on chemistry activity of PAW, and promoting the wide applications in biomedical field.