Study On Enzyme-controlled Mineralization Of Natural Polymeric Scaffolds And The Bone Inducing Properties

In recent years,due to congenital malformations,osteoarthritis and trauma caused by accident and other causes of bone defects in the number of patients increasing,the demands for its bone tissue engineering graft materials have been gradually increased.Bone tissue engineering scaffold material as a carrier of bone defects and bone injury material has always been the soul of bone tissue engineering.Therefore,it is necessary conditions to prepare the ideal composite scaffold material with bone conduction and inducing ability to successfully repair bone defect and bone injury.According to the structure and composition of natural bone,natural macromolecule/hydroxyapatite composite scaffolds synthesized by biomimetic mineralization with natural active macromolecules are the hotspots and core of this research field.The biomineralization method can simulate the morphology,size and crystallinity similar to apatite in natural bone to a certain extent,and make the composite scaffold material achieve the ideal mechanical and biological activity.Based on the study of a large number of literatures and the study of the research group itself,this paper selected two kinds of natural bioactive polymers such as Collagen and Chitosan as organic templates,the organic-inorganic composite bone repairing materials with three-dimensional porous structure and excellent properties were prepared by in situ polymerization of hydroxyapatite inorganic minerals in organic matrix scaffolds by dialysis method.Further,the differences between the two kinds of macromolecule organic template in nano-hydroxyapatite in biomineralization system were compared.In addition,n-HAP / COL composite scaffolds were used in the study of dorsal subcutaneous ectopic osteogenesis in rats and n-HAP / CS Composite scaffolds for the repair of femoral defect in New Zealand rabbits without the addition of growth factors and seed cells,and to indirectly compare the two kinds of composite scaffolds for bone regeneration and repair.This paper through the use of different organic matrix template,characterized by XRD,FTIR,TEM,SEM,TG/DTG,porosity and compression strength test,to study the changes in composition,structure,porosity,biocompatibility and mechanical properties for three-dimensional porous scaffold;The study of n-HAP / COL composite scaffolds in vivo mineralization experiments and rat subcutaneous ectopic osteogenesis experiments;and the n-HAP / CS composite scaffolds were used for the culture of MC-3T3 osteoblasts and the repair of femoral defect in New Zealand rabbits.The results show that the two kinds of composite scaffolds have abundant calcium and phosphate salts in the surface and internal pores,and these calcium phosphate salts are nano-hydroxyapatite.The composite scaffolds have interconnected pore structure and good mechanics strength,The porosity of aged 72 h n-HAP / COL was 72.78 ± 0.23%,compressive strength and compressive modulus were 230.23 ± 0.81 kPa and 465 ± 0.9kPa;and the porosity of dialysis 72 h n-HAP / CS was 96.0 ± 1.0%,compressive strength and compressive modulus were 0.44 ± 0.01 MPa and 0.20 ± 0.01 MPa,respectively.The in vivo study of n-HAP/COL composite scaffolds demonstrated the feasibility of in vivo mineralization of COL+Ca-GP group,but there was no ectopic osteogenesis ability of COL+Ca-GP+ in vitro ALP group;and the n-HAP / CS composite scaffolds in the animal body showed that the n-HAP / CS composite scaffold was more able to promote the repair of bone defects than the pure CS scaffold.After 12 weeks of implantation,Micro-CT and histomorphological staining showed that the repair of bone defect in n-HAP / CS group was basically completed.In addition,both n-HAP / COL and n-HAP / CS composite scaffolds have good histocompatibility in vivo.