## 4 Discussion  
The term wound refers to the damage to the human body caused by an external force that cuts the skin or other tissues, or leaves a subsequent partial defect in the tissue [23]. The dressings that are used to protect the damaged surface of a wound by preventing any leak of body fluids or the entrance of bacteria are called wound dressings, wound camouflages, or skin substitutes. Wound healing is a complex process that occurs though a series of steps that involve a number of different cellular activities. These steps determine the rate of healing, which is influenced by the release of bioactive materials such as growth factors, enzymes, carbohydrates, and proteins, as well as the inflammatory response to infection. When the skin is wounded, it is essential that the tissue is restored early on in order for the wound to be repaired in such a way that it resembles the original skin structure. Early wound closure is therefore vitally important, as an open wound that remains untreated for a long time may lead to a secondary complication such as infection, or leave a severe scar even after closure, causing functional or cosmetic problems [24]. The general methods for the treatment of wounds involve applying an antiseptic to the wound until closure, using a gauze or band type wound dressing to simply protect the wound, or using a dressing material containing a wound healing promoter. Nevertheless, a limitation of currently available wound dressings is that they encourage passive tissue regeneration that relies on the inherent regenerative capacity of the wounded area. Currently, an effective regenerative therapy is being sought to overcome this limitation. There have been attempts to transplant cells or tissues from another individual, or even from animals, as a way to produce a regenerative therapy; however, such methods are of limited use owing to the problems of immune rejection and an inadequate supply of therapeutic agents. These issues have prompted research toward developing an effective regenerative therapy for damaged skin tissues using tissue-engineering techniques that employ biomaterials [25]. To treat skin defects, studies are underway to deliver genes, growth factors, or drugs that are effective at the regeneration stage. In particular, since they provide more stable and efficient regeneration than the transplant of cells alone, there have been numerous studies using wound dressings, where cells such as fibroblasts, keratinocytes, and the matrix cells of adipose tissue are used for transplantation, as well as wound dressings that incorporate growth factors [26]. However, the integration of transplanted cells with the follicles found in healthy skin and the surrounding tissues has presented a challenge, indicating there is still an urgent need for the development of an efficient treatment method. When the cells of the body are damaged, VEGF plays a key role in the cellular regeneration process that occurs in response to the insult. On day 1 after wounding, platelets are produced, followed by the proliferation of endothelial cells and recruitment of macrophages by day 2. Following this, on days 3-4, neovascularization occurs via the formation of new capillary vascular endothelial cells. On day 5, new fibroblasts emerge, and granulation tissues are formed, leading to wound healing. VEGF plays a key role in these processes since it induces the proliferation and migration of endothelial cells (vascular and lymphatic cells) leading to the release of other growth factors (PDGF, TGF-\(\beta\), EGF, and FGF) that facilitate healing, and thus, the various bioactive substances work together to orchestrate the accelerated wound healing process [27]. In the present study a novel oxygen-releasing wound dressing was developed that promotes angiogenesis to allow for rapid wound healing. Angiogenesis generally occurs on days 3-4 after wounding (the angiogenesis zone), and if a stable adequate oxygen level is maintained until that time, angiogenesis is likely to be enhanced.