Effect of Additive Oxygen on the Reactive Species Profile and Microbicidal Property of a Helium Atmospheric Pressure Plasma Jet

Abstract

Microbial inactivation by cold atmospheric plasmas has been a subject of tremendous research interest in recent years, in part, due to the ambiguity concerning the plasma factors responsible for bacterial inactivation. This work investigated the efficacy of an atmospheric‐pressure plasma jet ignited in either helium or helium/oxygen mixtures in inactivating Escherichia coli on agar. The correlation of data obtained from inactivation experiments and a 2D model describing the gas dynamics and afterglow chemistry showed that the inactivation mechanisms differed qualitatively between the two gas compositions. This work also provides insight into the reaction pathways that lead to the production and destruction of the key active species and illustrates the importance in these processes of admixing ambient air.

Large-Scale Image Analysis for Investigating Spatio-Temporal Changes in Nuclear DNA Damage Caused by Nitrogen Atmospheric Pressure Plasma Jets

“…NO can also trigger the production of intracellular reactive oxygen species (ROS), which can initiate various pathways, including apoptosis. Similar observations of ring-shaped regions have also been reported in previous studies, such as the inactivation patterns of bacteria, the distributions of reactive species, theoretical modeling [42], and for a gas-shield, helium-based APPJ, during interactions with cancer cells [43]. After 8 h of incubation, the measured damage decreased, which was likely due to cell detachment.…”

Shielding‐gas‐controlled atmospheric pressure plasma jets: Optical emission, reactive oxygen species, and the effect on cancer cells

“…Due to low reactivity, O 3 is a long‐lived species, and it also has a slow rate of solvation into liquid; thus, the O 3 is able to travel in the He and shielding gas flow across the liquid surface. Larger plasma activation areas due to ozone production were also observed in our previous investigations when O 2 was premixed with He working gas . As for the ROS increase at shorter distances, even though atomic O quickly reacts with O 2 in the gas phase to produce O 3 , it can also be directly solvated into the liquid and converted into OH aq or O 3aq through O aq + H 2 O aq → OH aq + OH aq or O aq + O 2aq → O 3aq .…”

“…Acquiring this type of measurements is very challenging due to many technical issues, for example, liquid evaporation and surface deformation due to gas flow. To tackle these challenges and get a better understanding of effects on plasma species formation, computational efforts were used to assist in drawing conclusions . Here, we collected 2D high‐spatial‐resolution OES of the plasma jet that was directly in contact with liquid, and we created processing software to extract measurements of the intensity of a large number of emission lines as well as perform necessary chromatic aberration corrections.…”

Quantification of surface charging memory effect in ionization wave dynamics

“…This assumption takes into account the high repetition rate in experiments ( kHz) 71 . As in our previous works, the plasma model has been coupled with static flow COMSOL calculations 34 , 72 . For a similar jet system without target in Hofmans et al 57 , a comparison between flow calculations from the same model and radially-resolved Raman scattering measurements of air density (N + O ) has yielded a good agreement.…”