The Study On The Carriers Of Bone Morphogenetic Protein-2

Reconstruction of segmental bone defects caused by trauma, tumors, congenital malformation or corrective osteotomies remains an urgent problem in the orthopaedic field and bone morphogenetic protein-2 (BMP-2) is known for its potent osteoinductive properties in bone regeneration. So. to construct osteo inductic e bioresorbable carriers of BMP-2 has become the development trend in bone tissue engineering. Therefore, this paper carried out the following two studies.1. In this study, H2SO4-chitosan microspheres were prepared based on the reversible ion interaction between chitosan molecules and sulfuric acid using an emulsion-chemical cross linking method, and then the microspheres were treated by NaOH solution to form NaOH-chitosan microspheres. After studying on the influencing factors, the optimal preparing conditions were confirmed. It was found that the NaOH-chitosan microsphere had similar structure with chitosan and lower crystallinity via SEM, IR, and XRD characterizations. In the adsorption study, the NaOH-chitosan microspheres exhibited higher adsorption capacity to model protein BSA compared to H2SO4-chitosan microspheres and chitosan. Then the composite scaffolds of NaOH-chitosan microspheres (CMs) and absorbable collagen sponge (ACS) were conducted to study the release effect of rhBMP-2 in vitro. The rhBMP-2-loaded composite scaffolds were implanted into critical radius defects of rabbits and the ability of bone-repair was evaluated systematically.2. In this study, sodium carboxymethyl cellulose (CMC-Na), hydroxypropyl methyl cellulose (HPMC) and polyvinyl alcohol (PVA) were used to improve the mechanical property of the original BMP-2 carrier-calcium phosphate cement (CPC). The effect of modification was characterized. Further in vivo animal test was carried out to compare the ectopic bone formation and study on the biocompatibility. On this basis, the critical rabbit bone defect model was built, and CMC-Na/CPC and HPMC/CPC composite scaffolds were implanted into the defects and the ability of bone-repair was evaluated systematically.