# Wearable Plasma Pads for Biomedical Applications
## 3 Results and Discussion
### Wound Healing Effect of the Plasma Pad  
To evaluate the in vivo wound healing effect of the plasma pad, treatment was applied at each site after full-thickness excisional wounds were made on mouse back skin; wound closure in each group was observed using a stereomicroscope and the wound area was observed for 21 days after treatment.  
Plasma treatment significantly enhanced the rate of wound closure at Days 6 and 9 compared to that in negative controls (Figure 6a). The rate of wound closure in the plasma-treated group reached about 85.8% and 94.8%, respectively (\({}^{*}\)\(P<\) 0.05) compared to that in the control group (72% and 84%). This might be due to rapid re-epithelialization resulting in the promotion of cell proliferation and/or migration, thereby facilitating wound healing. Additionally, we assume that the increased exogenous NO in the wound area and around tissues promoted angiogenesis and enhanced cellular growth for wound healing. This is supported by several previous studies reporting that NO resulted in angiogenesis triggering cellular growth and differentiation in a wound model [38; 39; 40; 41].  
As shown in Figure 6b, the wounded skin fully recovered without any contraction or crusting in plasma-treated mice, whereas some crusting was found in the negative control group at Day 21.  
To confirm wound healing efficacy, recovery was evaluated by using the rate of skin re-epithelialization, remodeling, and repair in each slide sample after staining with H&E. The rate of wound repair in the plasma-treated group was 1.3-fold higher than that in the negative control group, calculated as 12.5% in negative controls and 16.7% in the plasma-treated group. This indicates that plasma treatment induced accelerated wound repair at Day 21 compared to the controls. Histological analysis also exhibited the same result as shown in Figure 6c. The histological images of skin treated with plasma showed re-epithelialization with thick epidermis and increased dermal fibroblasts, resulting in dense dermal fiber, remodeling with some skin adnexa including hair follicles and dense dermal fibroblast, and complete wound repair with skin adnexa and increased hair follicles. Hair follicles in anagen and catagen stages were significantly increased compared with the control group, as shown in Figure 6d. On the other hand, compared with the plasma-treated group, the negative  
Figure 5: Exogenous nitric oxide (NO\({}_{2}^{-}\)) and in vitro capillary tube formation with plasma treatment. (a) Quantitative analysis of NO\({}_{2}^{-}\) generated by a plasma pad (\(n=4\), \({}^{*}\)\(P<\) 0.005, \({}^{**}\)\(P<\) 0.0005 compared to control); (b) Images of capillary tube formation by HDMVECs with plasma treatment and quantitative analysis of capillary tube length (\(n=5\), \({}^{*}\)\(P<\) 0.005, \({}^{**}\)\(P<\) 0.0005 compared to control). Scale bars are 100 \(\upmu\)m.  
control group showed re-epithelialization of thin epidermis, skin remodeling with fewer dermal fibroblasts, less deposition of collagen, and wound repair with fewer total hair follicles and increased telogen-stage follicles.  
The overall rate of wound healing in the plasma-treated group was enhanced in comparison with that in negative controls. These results indicate that remodeling of skin tissue through re-epithelialization is faster in the plasma-treated group than in the negative control group, resulting in an increased rate of wound repair.