A comparative study of the major antimicrobial agents against the yeast cells on the tissue model by helium and air surface micro-discharge plasma

Abstract

Surface micro-discharge (SMD) plasma with a large-area and homogeneous discharge has attracted much attention in the skin disinfection due to its high antimicrobial efficiency and less side effects on tissues. Although SMD plasma sterilization is undisputedly attributed to the reactive oxygen and nitrogen species (RONS), the exact RONS speciation on the tissues and their individual contribution to the plasma inactivation are still not fully understood. Herein, we investigated the generation and distribution of hydroxyl radical (·OH), hydrogen peroxide (H2O2), ozone (O3), nitrite (NO2-), and peroxynitrite/peroxynitrous acid (OONO-/ONOOH) on the agarose tissue model and their contribution to yeast inactivation by helium (He) or air SMD plasma at different irradiation distances. The results show that He and air SMD plasma exhibited different RONS speciation and antimicrobial activity. The He SMD plasma mostly generated ·OH and H2O2 on the tissue model, which were concentrated in every hexagon micro-discharge unit and decreased with the irradiation distance, while the air SMD plasma mainly produced O3, NO2-, and OONO-/ONOOH, which were uniformly distributed on the whole tissue model. More importantly, the ·OH generation on the tissue model by the He SMD plasma was derived from the plasma delivery, while UV photolysis led to the in situ ·OH generation by the air SMD plasma. Additionally, the air SMD plasma has a higher inactivation efficiency than the He SMD plasma and the major antimicrobial agent for He and the air SMD plasma is, respectively, ·OH and O3 in this plasma-tissue interaction system.