Abstract: The shortage of skin for grafting continues to be a major problem in the treatment of serious skin injuries. 3D bioprinting provides a new way to solve this problem. However, current 3D printed skin is less effective in treatment of large wounds because of severe shrinkage and scarring. In this study, bionically designed bilayer skin was fabricated using an extrusion-based bioprinter and a gelatin/sodium alginate/gelatin methacrylate hydrogel with excellent physical and biological properties. Full-thickness skin wounds were created in the back of nude mice and treated with bioprinted skin or hydrogel. Bioprinted skin accelerated wound healing, reduced wound contraction and scarring, and facilitated wound skin epithelialization compared with the bioprinted hydrogel or untreated wound. The skin from the wound was collected 28 days after grafting for histology and immunofluorescence analysis. The thickness of the dermis and epidermis of the bioprinted skin was similar to that of nude mice. Microvascular formation in the dermis and dense keratinocytes in the epidermis of the bioprinted skin were observed. This study provides a potential treatment strategy for reducing skin contraction and scar in large skin wounds.

Key words: 3D bioprinting, bionic design, skin substitutes, wound healing, reducing scar