Wound Healing Effect of Non-Thermal Atmospheric Pressure Plasma Jet on Rat Burn Wound Model

Introduction: Burn injury mortality across the world is very high. It is characterized by central zone of necrosis surrounded by zone of ischemia which will eventually become necrotic cells due to homeostasis impairment. Plasma medicine, which has been known for its positive effects in wound healing, was developed to cope with it. Plasma medicine is a new technology in medical field and have many medical purposes including wound healing and tissue regeneration. Reactive species produced by plasma can diffuse into the cell and cause oxidative stress. Therapeutic of this technology depends on the strength of oxidative stress. Moderate oxidative stress may result in wound healing promotion whereas excessive oxidative stress may result in toxic product. There have been many cases where reactive species have been proven to improve wound healing. In this study, we examined the effect of non-thermal atmospheric pressure plasma jet (NAPPJ) on rat brass comb burn model. Methods: Burn wound model was made by using pre-heated (100oC) brass combs with four prongs separated by three 5 mm notches that would produce 3 unburned sites (interspaces) between the 4 burned sites and then perpendicularly applied to the back skin without pressure for a period of 90 seconds. Interspaces of hairless rats were exposed to NAPPJ treatment for 2 minutes once per day. Skin biopsies were collected at day 0, 4 and 7 post wounding. The samples were subjected for histology and mRNA quantification analysis. Results: 6 rats were used in this study and a total of 18 interspaces were analyzed. We found that the percentage of interspace that underwent necrosis was higher in control group than plasma treated group (51.8 �� 20.5 versus 31.5 �� 19.0, P = 0.0000179). The exposure of interspace to NAPPJ also greatly reduced the number of infiltrating neutrophils. In addition, we also found that the number of interspace that underwent full-thickness necrosis in plasma treated group is smaller than control group (28% versus 67%). mRNA expression quantification also showed that plasma treatment could improve wound healing by significantly reducing the expression of pro-inflammatory cytokines (Tnf-�� [p value 0.044, 0.029, and 0.125, for day 0, 4, and 7 respectively] and Il-1�� [p value 0.009, 0.016, and 0.01, for day 0, 4, and 7 respectively]), upregulation of iNOS [p value 0.001 and 0.001, for day 0 and 4 respectively, and downregulation at day 7 with p value 0.01], anti-inflammatory cytokines (Tgf-�� [p value 0.017, 0.036, and