Development And Characterization Of Collagen-Based Artificial Skin

As the largest organ of the human body,the skin consists of epidermis and dermis.It’s difficult to heal the full thickness wound which caused by mechanical injury,burns and other factors.Skin grafts have been used for a long time as a solution to heal wounds.However,since the use of autografts,allografts,and xenografts have severe drawbacks,such as source limitations,immunological rejection and potential risks of virus transmission.The artificial skin constructed by tissue engineering has the advantages of wide sources,low immune rejection and no potential disease transmission.Therefore,it is currently an effective method for repairing the full-thickness skin wound.It’s difficult for the tissue engineering artificial skin with monolayer structure to mimic the epidermal-dermal structure of skin.As the main component of skin dermal,collagen has advantages of good biocompatibility,bioactivity and low immunogenicity,and can effectively promote the healing of skin wound.However,the existing collagen-based artificial skin has disadvantages such as poor mechanical properties and biotoxicity of crosslinking agents.Therefore,the construction of collagen-based artificial skin that simulates full-layer skin structure and has good biocompatibility has always been a research hotspot in biomedical and other fields.This thesis aims to design and develop collagen-based artificial skin with composite structure to achieve the purpose of bionic full-layer skin structure and function,and to study its mechanical properties,biological activity and ability to promote full-layer skin damage repair.The contents are as follows:1)Biomaterials with highly bionic skin multilayer structure are of great significance in the treatment of skin injury repair.We successfully constructed a collagen-based artificial skin to mimic the epidermis-dermis structure of skin.The structure of the artificial skin from top to bottom is silicone membrane layer,collagen membrane layer and collagen sponge layer,respectively.The collagen membrane-collagen sponge double-layer scaffold material prepared by gradient heating freeze-drying method and double cross-linking method simulates the dermis of skin,and the silica gel membrane layer above simulates the epidermis of skin.The structural characteristics,anti-dissolution,anti-swelling,anti-degradation and mechanical properties of dermis were systematically studied.We found that collagen-based artificial skin has a multi-layer structure with good interface bonding and appropriate pore size,which can play the role of outer barrier and internal scaffold in wound healing.The results of swelling ratio,dissolution rate and tensile strength showed that the dermis of the artificial skin had good mechanical properties,stable structure,water absorption and retention,and could transport nutrients and metabolites for wound repair.In addition,dermis materials have suitable degradation properties,which can provide a scaffold function while avoiding the problems of secondary debridement and material residue.The new collagen-based artificial skin has great potential in absorbing exudate of skin wound,transporting nutrients and promoting cell adhesion and proliferation.2)Biological evaluation of materials follows two major principles: biosafety and bioactivity.Good biological evaluation is the decisive factor of whether biomaterials can be used in clinical experiments.The biocompatibility and bioactivity of collagen-based artificial skin were studied by cytotoxicity,cell proliferation and material-cell interaction.The results of cytotoxicity,cell proliferation and live/dead cell imaging showed that the collagen based artificial skin had no cytotoxicity,promoting cell proliferation and good cell morphology.At the same time,artificial skin has good cell adhesion ability and can provide scaffold for suspended cells.The results indicated that the artificial skin can promoted the cells proliferation and migration.The collagen membrane layer could act as a secondary barrier to provide a suitable environment for the cells.The good biocompatibility and bioactivity of artificial skin are beneficial to tissue repair,regeneration and structural remodeling in full-thickness skin wound healing,which provides theoretical support for the replacement of full-thickness skin wound materials.3)The safety of artificial skin in vivo and its effectiveness in healing full-thickness skin wound are the important basis of artificial skin as wound defect repair material.The biosafety of the collagen-based artificial skin was investigated by pyrogen and hemolysis experiments,and their healing ability was studied by full-thickness skin wound model in SD rats.The collagen-based artificial skin is non-pyrogenic and has no hemolysis and good biosafety.The collagen based artificial skin was applied to the full-thickness skin injury model,and the wound was healed completely on day 25,and the new skin surface was smooth without hyperplasia.H&E staining results showed that the collagen-based artificial skin had good tissue regeneration ability.Masson staining results demonstrated that the collagen-based artificial skin has the ability to promote the expression of collagen fiber,which was conducive to the regeneration and repair of collagen fiber in the dermis of the wound,and effectively promoted the healing of the full-thickness skin wound.The collagen-based artificial skin with biosafety and tissue regeneration provides a new therapeutic strategy for full-thickness skin wounds,which has great potential in the field of biomedicine.