Construction Of Paracrine System Based On Photo-Crosslinked Hydrogel Microsphere Carrier And Its Application In Skin Wound Repair

Skin wound is very common in clinical practice.Wound dressing is a material used for covering sores,wounds or other damage,which has a barrier outer structure,which can prevent microbial invasion in the environment and prevent wound from cross infection and secondary damage.The main strategy of current hydrogel dressings for skin wound repair is to load anti-inflammatory or restorative drugs into hydrogel dressings by chemical or physical methods,but hydrogel dressings loaded with slowrelease factors also face the problem of limited load and cannot guarantee the successful release of factors on hydrogel scaffolds.After in-depth exploration of the literature in the field of skin wound healing,we found that continuous production of pro-repair factors by living cells is a better strategy to improve the pro-repair performance of wound dressing.This paper explores the preparation and application of a threedimensional cell culture system that simulates the main components of extracellular matrix.The culture system is explored in three parts:Firstly,the gelatin was grafted with methylacrylylation to a certain extent,and the proportion of collagen and polysaccharide in the cytoplasmic matrix was simulated.The gelatin and methylacrylylation gelatin were uniformly blended with sodium alginate,respectively,to explore the effect of group grafting on cell proliferation and factor secretion behavior.A complete and regular cell-carrying composite gel microsphere was prepared in the experiment.It was found that the thermosensitive crosslinking gelatin/sodium alginate composite gel microsphere had an obvious promoting effect on cell proliferation,while the photocrosslinking methylacryylated gelatin/sodium alginate composite gel microsphere had an obvious advantage in promoting the expression of parasecretation-related genes in cells.Then,based on the preparation method of photocrosslinking hydrogel,the concentration of GelMA was controlled,and the concentration of SA was changed(0.5%in the low content group and 2.0%in the high content group)to regulate the content of polysaccharide in the cell culture environment,and the influence of polysaccharide on cell proliferation and factor secretion behavior was compared.It was found that the relative gene expression of paracrine cells was positively correlated with the polysaccharide content in the composite gel microspheres,in other words,the composite gel microspheres with higher polysaccharide content were more conducive to the paracrine effect of paracrine cells.Mouse mononuclear macrophage leukemia cells(RAW264.7)was to inhibit inflammation and help the wound successfully pass the inflammatory period,while the main effect adipose tissue-derived stromal cells(ADSCs)were reflected in the cell proliferation period,helping the wound to accelerate tissue growth and matrix remodeling.Scratch test and wound tissue staining showed that the wound healing effect was the best when the two cells acted together.In addition,the results of mouse organ staining showed that the treatment of the experimental group did not cause organ damage.No abnormalities in basic signs were observed in the blood tests and weight monitoring results of the mice.In summary,the paracrine effect system prepared in this paper,constructed by paracrine cells and composite gel microsphere carrier,has been applied in both in vitro and in vivo models of skin trauma after optimizing the cross-linking mode and polysaccharide content of the carrier,which indicates that the paracrine effect system we studied has the function of promoting skin wound repair.