Evaluating the roles of OH radicals, H₂O₂, ORP and pH in the inactivation of yeast cells on a tissue model by surface micro-discharge plasma

Abstract

Surface micro-discharge (SMD) plasma holds great potential as an effective, economical and safe method for the treatment of diverse skin infections. Although the antimicrobial effect of SMD plasma is undisputed, the factors most responsible for the inactivation effect and their corresponding killing mechanisms are still not fully understood. Herein, we evaluate the roles of hydroxyl radicals (•OH), hydrogen peroxide (H 2 O 2 ), oxidation-reduction potential (ORP) and pH in the inactivation of yeast cells on an agarose tissue model by helium SMD plasma over different irradiation distances and time periods. The •OH distribution pattern shows that •OH is mostly produced in the center of every hexagon mesh electrode, whose concentration is closely related to humidity and is markedly increased at a shorter irradiation distance and longer treatment time. Meanwhile, the killing pattern of yeast cells corresponds to •OH distribution and the inactivation efficiency has a similar trend to that of •OH concentration. The results of Pearson correlation analysis reveal that the inactivation efficiency is more dependent on •OH and pH compared with H 2 O 2 and ORP. Furthermore, we investigated the effects of •OH and pH on yeast cell viability, membrane integrity and intracellular ROS and pH homeostasis by using a specific •OH scavenger D-mannitol (D-man) and phosphate buffer solution (PBS). The results showed that D-man could significantly reduce the inactivation efficiency by maintaining cell membrane integrity and intracellular ROS and pH homeostasis, while PBS only slightly mitigates the plasma-caused damage on yeast cells. Based on the results, it is concluded that •OH contributes most to the inactivation of yeast cells on a tissue model by helium SMD plasma studied here.

Multi-Hollow Surface Dielectric Barrier Discharge for Bacterial Biofilm Decontamination

“…The inactivation of bacteria is dependent on biofilm thickness, the penetration depth of active particles and induced secondary products. Thus, hydrogen peroxide and OH radicals are very important in the process [ 2 , 11 , 37 ]. To test the effect of plasma-activated media compared to water vapor, we exposed the S. aureus biofilm to condensates and physiological solution (control sample).…”

“…The OH radical itself directly impacts microorganism cell membranes and provides inactivation of various pathogens [ 10 , 11 ] due to its highest oxidation potential [ 12 ]. Various LTPs have been developed to generate OH radicals by water molecule dissociation.…”

Cold atmospheric plasma applications in dermatology: A systematic review

“…Antifungal treatment is another scope for plasma treatment in dermatology since the excellent killing of the most clinically relevant fungal strains by CAP has been shown in vitro. A significant reduction of fungal targets after plasma treatment has also been shown on fungal infection model nails and toenails [52–54]. Taken together, these studies indicate a promising application of CAP as an innovative therapy for onychomycosis.…”

Atmospheric pressure plasma treatment induces abscisic acid production, reduces stomatal aperture and improves seedling growth in Arabidopsis thaliana

“…Temperature and humidity of the chamber during the experiment were monitored with temperature and humidity sensors, and O 3 concentration in the chamber was measured with an O 3 detector (NGP5‐50‐O 3 ; Ningbo Gaopin Technology, Ningbo, China). Following Xu et al (2019). The pH of the aqueous solution was determined with a pH meter (LE438; Mettler‐Toledo, Zurich, Switzerland); OH was measured using terephthalic acid; H 2 O 2 concentration was determined using a Hydrogen Peroxide Assay Kit (Beyotime, S0038, Beijing, China).…”