A better approach for biofilm-control: atmospheric-pressure He/O2 plasma jet

The vast majority of bacteria in nature are attached to the surface of living or non-living items and grow in the form of biofilms. A bacterial biofilm has a high resistance to antibiotics and host immune defense systems leading to serious clinical problems, such as biofilm-contaminated human skins, canal roots, and biomedical-device-driven chronic and refractory infections. Among these, the S. aureus biofilm is the main cause of medical implant infections which largely compromises wound treatment.

Atmospheric-pressure low temperature plasma is an electrically neutral medium composed of unbound positive and negative reactive particles and is proven to be an effective approach in microbial biofilm inactivation due to merits including high efficiency, no toxic residues, and low treatment costs.

(b) SYTO 9/PI stained CLSM images on bacterial membrane integrity of the He/O2 (0.5%) APPJ treated S. aureus biofilms for different plasma dose and biofilm layers.

(a) SYTO 9/PI stained CLSM images on bacterial membrane integrity of the He/O2 (0.5%) APPJ treated S. aureus biofilms for different plasma dose and biofilm layers.

In this work, we study the antimicrobial effects and associated mechanism of plasma inactivation on S.aureus biofilm, which is the synergistic effect due to APPJ generated ROS (Reactive Oxygen Species) and the induced intracellular endogenous ROS (reactive O and ·OH, etc.). Bacterial surface morphology, metabolic capacity and the membrane integrity of the biofilm S. aureus after plasma treatment have changed dramatically.

(a) HDCFDA stained CLSM images acquired from the 6th layer of the He/O2 (0.5%) APPJ treated S. aureus biofilms. The highly fluorescent DCF serves as an indicator of intracellular ROS.

(b) H2DCFDA stained CLSM images acquired from the 6th layer of the He/O2 (0.5%) APPJ treated S. aureus biofilms. The highly fluorescent DCF serves as an indicator of intracellular ROS.

Interestingly, we find that some intact S. aureus cells are in areas with high concentrations of ROS, which signifies higher resistance to ROS of these bacteria. In the following work, we will focus on this point and sort these bacteria thus detecting its gene expression. Maybe the progeny bacteria would inherit the feature of high resistance to intracellular ROS, even higher? It would be a breakthrough if the related gene expressions of the progeny bacteria really changed. In that condition, the biological safety issue which plasma treatment could bring about in curing microbial biofilm-related diseases should be taken into account in clinical applications.

About the authors

Zimu Xu is lecturer in the School of Resources and Environmental Engineering at the HeFei University of Technology, China. He gained his B. S and Ph. D in the University of Science and Technology of China and his research focuses on biological and environmental applications of low temperature atmospheric pressure plasmas.

Jie Shen is associate professor in the Institute of Plasma Physics, Chinese Academy of Sciences, China. His research interests include experimental plasma and gas discharge diagnostics, discharges in liquid phase, and plasma applications in medicine and biology.

Cheng Cheng is associate professor in the Institute of Plasma Physics, Chinese Academy of Sciences, China. His research interests include low-temperature plasma sources, plasma diagnostics, plasma medicine, surface modification, as well as nanostructured materials.

Shuheng Hu is associate professor in the School of Resources and Environmental Engineering at the HeFei University of Technology, China. She focuses on the environmental application of low temperature plasma technology.

Yan Lan is associate professor in the Institute of Plasma Physics, Chinese Academy of Sciences, China. Her research interests include various plasma excitation technique, plasma applications in chemical synthesis, plasma medicine, air pollution abatement, ion exchange membrane preparation and surface modification.

Paul K Chu is Chair Professor of Materials Engineering in the Department of Physics and Materials Science in City University of Hong Kong. His research is quite diverse, encompassing plasma and materials science & engineering.


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Categories: Journal of Physics D: Applied Physics, JPhys+

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