Self-Healing Injectable Hydrogel Based On Natural Polymers For Applications As Cell Scaffold

Hydrogels are usually prepared by structural modification,physical interaction or chemical crosslinking.The triggering of various environmental factors,such as temperature,pH,ionic strength and physicochemical interaction,has also been used to form physical hydrogels.It includes multiple processes of coagulation(frequent freezethaw cycles leading to the formation of frozen gel)and ion interaction.In addition,photopolymerization,enzymatic reaction,and chemical crosslinking methods using glutaraldehyde,borate,glyoxal and other crosslinking agents through polymerization,copolymerization and covalent chemical interaction have been used to manufacture chemical hydrogels,which can achieve enhanced stability and excellent mechanical strength.Another method is to use radiation grafting,including gamma radiation,ultraviolet radiation,and high-energy electron beam radiation,depending on the time and intensity of the radiation.Crosslinked hydrogels are highly stable,have a permanently fixed shape at rest,and are usually irreversible.The hydrogel based cell scaffold can provide a specific cell survival environment similar to the target tissue.The specific topological structure and internal structure of hydrogel can conduct passive mechanical stimulation from the boundary surface of biomaterials,and allow to regulate the tissue morphology,promote cell aggregation,and promote multi cell interaction,thus triggering the formation of three-dimensional microstructures.The materials used to form hydrogels should be biocompatible,easy to regulate and promote cell growth,and have structural characteristics similar to real tissues.Hyaluronic acid and chitosan are polysaccharides widely used in tissue engineering applications.Both hyaluronic acid and chitosan are glycosaminoglycan types composed of similar disaccharide repeating units.Glycosaminoglycans are commonly used in the formulation of biomaterials due to their involvement in cell signal transduction and communication.Both polymers are biodegradable and non-toxic,despite their poor mechanical stability.No single polymer material can summarize the complexity of the microenvironment and natural extracellular matrix in vivo.Natural polymers contain bioactive signals that promote cell growth and proliferation,but they can vary due to their poor mechanical and stability issues.The stability and modulus of hyaluronic acid and chitosan can be changed by utilizing their hydroxyl groups and amino groups.In this work,self-healing injectable hydrogels were prepared by Schiff base reaction between N,O-carboxymethyl chitosan(NOCC)and oxidized aldehydecontaining hyaluronic acid(A-HA).The obtained hydrogels were characterized by Fourier transform infrared spectroscopy and scanning electron microscopy.The rheological property,swelling property and self-healing property of the hydrogel were determined.Hydrogels have interconnected porous structure,high swelling ratio and excellent self-healing ability.Cytotoxicity test and zebrafish embryo toxicity test proved the biocompatibility of hydrogel.Human umbilical cord blood mononuclear cells were encapsulated in hydrogel,and after 21 days of culture,high cell viability of more than50% was obtained,which demonstrated the positive effect of NOCC/A-HA hydrogel on cell survival in vitro.The scald model of mice was made to evaluate the potential of cell carrying hydrogel in wound healing.Compared with the control group and the hydrogel group,the cell loaded hydrogel group showed faster epidermal regeneration,reduced inflammation and more new blood vessels,which indicates that human umbilical cord blood monocytes are conducive to skin re epithelization.It was confirmed that NOCC/A-HA hydrogel combined with cord blood mononuclear cells significantly enhanced the neovascularization of the wound surface of mice without scar formation in the treatment of deep second degree scald model in mice.Therefore,NOCC/A-HA hydrogel encapsulating human umbilical cord blood mononuclear cells may be a promising treatment for burns or scalds.In conclusion,this work focuses on the preparation of self healing injectable hydrogel cell scaffolds with good biocompatibility by using simple methods.By exploring the effects of different material ratios on the structure,rheological properties,swelling properties and biocompatibility of hydrogels,we can obtain the most suitable hydrogel for use.The combination of hydrogel cell scaffold and human umbilical cord blood mononuclear cells in the application of deep second degree scald wounds has potential application prospects in wound repair and scar reduction,which lays a foundation for further application in clinical treatment.