Effect of low-temperature plasma on wound healing of mouse skin

Objective: To compare the different doses of low-temperature plasma (LTP) on wound healing in BALB/c mice so as to discuss the effects of the optimal dose of low-temperature plasma dealing with wound in mice and the acting mechanism of wound healing. Methods: Adoptatmospheric pressure plasma jet discharged by the dielectric barrier was used to treat mouse skin wound. According to the processing time, the wounds were divided into 10 s, 20 s, 30 s, 40 s and 50 s experimental groups, while naturally healing wounds served as negative controls and the wounds dealt with recombinant human epidermal growth factor served as positive controls. We recorded the wound size every day, observed the histopathological changes, the expression level of type I collagen by immunofluorescence, and analyzed the composition of low-temperature plasma jet. Results: The wounds with plasma treatment time of 10 s, 20 s, 30 s, and 40 s showed significant daily improvement and almost complete closure at days 12, 10, 7, 13, respectively. However, the wounds with plasma treatment time of 50 s remained unhealed at day 14. The wounds in positive control group all healed, and the wound healing effect in positive control group could be achieved in 30 s group. HE staining and immunofluorescence staining assays showed the optimal result of epidermal cell regeneration, granulation tissue hyperplasia, and collagen deposition in histological aspect at day 7 in 30 s group. The low-temperature plasma jet contained highly reactive free radicals of nitrogen and oxygen, which play an important role in wound healing process. Conclusion: Appropriate doses of cold plasma can accelerate wound healing whereas over-doses of plasma can suppress wound healing. The process of wound healing may be related to reactive oxygen and nitrogen species in LTP.