Chitosan/Dextran/nano-Hydroxyapatite Composite Hydrogel For Conducting Bone Regeneration

Hydrogel as a scaffold material has been applied in the field of bone tissue engineering,but the solubility of natural hydrogel in physiological status is poor,the mechanical strength is weak,yet there only a few study of hydrogel's application on the large bone defect's repair.We choose modified chitosan and dextran to form the composite hydrogel as scaffold materials,for they can form dynamic covalent imine bonds(Schiff base)to gift the composite hydrogel the self-healing ability and the internal porous intertwined structure.Meanwhile,the mechanical strength is enhanced with the addition of nano-hydroxyapatite(nHAp),which can better suffer the pressure from surrounding tissues.In this study,we research the physical and chemical properties,biological properties,the function on bone defect regions of the composite hydrogel,to wonder if the composite hydrogel can be as the scaffold material on bone tissue engineering's application.Objective: In this study,we design chitosan/dextran/nHAp injectable composite hydrogel,and explore the physical and chemical properties and biological properties,the ability on bone defect repairing,in order to explore the mechanism of chitosan/dextran/nHAp as scaffold material,and the feasibility of its application in the field of bone tissue engineering.Methods: First,we prepare this two kinds of composite hydrogel precursor solutio n: N-carboxyethyl chitosan(CEC)and Oxidized Dextran(ODex),then test the physical and chemical properties,cell toxicity and biological compatibility.Suspend nHAp into CEC,then put this two kinds of precursor solution in the double-pipe syringe,inject the composite hydrogel into the bone defect area after the rats skull defect model finis hed,after 8 weeks and 12 weeks with X rays in vivo imaging and tissue slice staining to evaluate the cambium of the bone defect area.Results: The self-healing ability is attribute to the dynamic imine bonds as demonstrated by macroscopic observation.The rheological measurement indicate a fast gelation time,suitable strength.The free aldehyde of hydrogel and amine of surrounding tissue formation imine reaction to sustain tissue integration.In vitro cytotoxicity analysis and in vivo degradation demonstrate that it is promising for good tissue biocompatibility.After the material was injected into the bone defect region for 8 or 12 weeks,both results of X-ray in vivo imaging and histological sections show that the composite hydrogel with nHAp exhibits faster and better bone repair ability.Conclusion: This study indicates that the modified injectable self-healing composite hydrogel can promote bone repair ability on the bone defect regions,which can provide the basis on bone tissue engineering's application for hydrogel scaffold.