Surface air discharge used for biomedicine: the positive correlation among gaseous NO ₃ , aqueous O ₂ ⁻ /ONOO ⁻ and biological effects

Abstract

Abstract 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 NO 3 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 NO 3 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 NO 3 to aqueous ONOO aq − /ONOOH aq and O 2aq − 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 ONOO aq − /ONOOH aq and O 2aq − , and the density of gaseous NO 3 , implying that NO 3 might be very important for the production of aqueous short-lived reactive species as well as the biological effects induced by plasma-activated solutions.