Research Of Biomimetic Nanofibers For Chronic Wound Healing

Because the skin tissue is exposed on the surface of the body,it can be easily damaged.However,the wounds on the skin and even the chronic wounds threaten the life and health of people seriously and bring a heavy social medical burden.It is difficult for existing wound repair materials to meet the clinical needs,the ideal skin regeneration materials should be able to induce the cells to be involved in the repair process,which requires the material to maximumly simulate the natural skin extracellular matrix.The two most important features of the natural extracellular matrix are its structure and composition.Electrospun nanofiber membranes are an ideal wound dressing because the morphology and size characteristics of nanofibers prepared by electrospinning are similar to the collagen fibers in the natural extracellular matrix of skin tissue.Therefore,two types of electrospun nanofiber membranes were prepared in this study,including structural biomimetic nanofiber membranes and component biomimetic nanofibrous membranes.Through in vitro experiments and in vivo animal experiments,we are able to study the structure and composition effects of nanofibrous membrane on the regulation of different cells,as well as their effects on the healing process of refractory wounds,the main work and conclusions in this study are as follows:(1)We used PCL and type I collagen as raw materials,and crossed nanofibers were prepared by electrospinning with a flat-plate electrode to biomimetic the natural extracellular matrix of skin tissue.The interaction between nanofibers and human dermal fibroblasts was compared.The effect of random fibers,aligned fibers and crossed fibers on the migration and gene expression of fibroblasts in vitro was investigated.It was found that the morphology of the cells in the aligned fiber was elongated,while the cells in the crossed fibers were star-shaped and adherent to the fiber scaffold.At the same time,orieneted fibers can significantly promote the migration of HFFs and up-regulate the expression of genes related to wound healing,among which the crossed fibers have the most obvious regulation on cells and it has the potential to inhibit the formation of scar tissue.(2)The model of type I diabetic rats was constructed,and the nanofiber membranes with different orientations were used in the full thickness wounds.The wound healing rates were compared and analyzed among groups by pathological sections and immunochemical staining.We found that nanofiber membrane can promote wound healing to varying degrees and reduce the degree of inflammation.Among them,the aligned and crossed nanofibrous membranes can better promote the transition of macrophages from M1 to M2,thus helping to solve the inflammatory phase in wound healing process.Crossed nanofiber membrane can promote wound reepithelialization,and the crossed nanofiber membrane can accelerate the formation of new blood vessels in the wound site,so as to better provide nutrients and oxygen for granulation tissue.In summary,the crossed nanofibrous membrane can improve the healing rate of diabetic wounds and promote better wound healing.(3)Coaxial nanofibers with PLGA and type I collagen as the inner layer and PLGA and fibrinogen as the outer layer were prepared by coaxial electrospinning technique to simulate the dynamic changes of extracellular matrix components during wound repair process.The effects of this material on ASCs proliferation and gene expression as well as the effect of material-induced ASCs conditioned medium on macrophage polarization were investigated.We found that the nanofibers have a typical coaxial structure,and they can effectively up regulate wound repair related genes,angiogenesis related genes and immune-related gene expression.Meanwhile,ASCs induced by this coaxial fiber can secrete related cytokines to induce the conversion of macrophages from inflammatory phenotype(M1)to repair phenotype(M2),thereby promoting the process of refractory wound healing to the proliferative phase transition.In summary,we successfully prepared two kinds of nanofibers in this study,and through a series of in vitro and in vivo experiments showed that the fibers have good biocompatibility,and can promote better wound healing.We believe the aboved two kinds of nanofibers will provide new ideas for the treatment of clinical wounds.