Multiphysics modeling of gas plasma-based wound healing process

Wound healing is one of the promising applications of atmospheric pressure gas plasmas in medicine. Recent clinical studies show a significant reduction of bacterial load in treated wounds without any side-effects. [1] Plasma-generated reactive oxygen and nitrogen species (RONS) are thought to be directly or indirectly responsible for the bacterial elimination. We have been developing a multiphysics model of plasma-based wound healing process. In this study, we focus on surface micro-discharge (SMD) [2] and developed a zero-dimensional fluid model with approximately 50 species and over 500 reactions. Our simulation results indicate that various reactive species are generated, including O, OH, O₂*, O₃, H₂O₂, HO₂, NO, NO₂, HNO₂. Previous experimental results indicated that those reactive species have temporal and long-term bactericidal effect. [2-4] In order to investigate the short- and long-term antimicrobial effect of plasmas on wound healing, we adapted a five species mechano-chemical model of epithelial wound healing. [5] The model follows the spatial and temporal profiles of oxygen, chemo-attractants, capillary sprouts, blood vessels, fibroblasts, and extracellular matrix. We assumed that a wound is exposed to SMD for 5 minutes at every 12 hours. The plasma treatment has the initial reduction of bacterial load and the delay of bacterial growth rate. The reduction of bacterial load increases oxygen concentration in wound and promote the healing process. Our preliminary simulation result shows that the prolonged effect of plasmas is important and that the initial reduction in the bacterial population may not be sufficient for improved healing. Although our current model is still in the early stage, the present results suggest several important directions for coupling plasma models with models of tissue biochemical responses.