| Objective:The studies were carried out to investigate the biocompatibility and the effects on bone formation of three-dimensional porous poly(lactic-co-glycolic) (PLGA) (75:25). Whether the PLGA coated with Calcium Alginate gel (CAG) enhanced its biomechanics and optimizing the properties. Provide an experimental reference for the function of composites. Discuss the osteoinductive ability of scaffolds consisting of recombinat human bone morphogenetic protein-2 (rhBMP-2),vascular endothelial growth factor (VEGF) and CAG,and evaluate the prospective useage in orthopaedics,develop a new kind of absorbable osteosynthesis material.Methods:High porosity foams of PLGA were fabricated by lower-heating and compressive method,modified with CAG and that combined with rhBMP-2 or VEGF. Successive studies were done in such ways:1. Experimental studies on the biocompatibility of three-dimensional porous PLGA composites.In vitro biocompatibility test. Osteoblasts derived from the calvaria of neonatal Sprague-Dawley rats cultured with PLGA and PLGA/CAG. Samples were examined by light,enviromental scanning electronic microscope (ESEM) and MTT assay to evaluate the adhesiveness and proliferation of osteoblastic cells.2. Bone formation study of scaffolds.Bone defects of 1.0cm were made on the radial of New Zealand white rabbits,andPLGA,PLGA/ CAG,PLGA/ CAG / rhBMP-2,PLGA/ CAG /VEGF foams were implanted in the fields. The samples were examined by X-ray over the whole period,and the specimen were harvested in 2,6,12 week for histology test,scanning electronic microscope (SEM) evaluation test were done for the implantation after 2,6th week,the biomechanical test (bending strength) was employed to study the quality of bone formation for the 8,12 week one.Results:1. Materials cultured with osteoblastic cells revealed no cytotoxicity and polymers were tolerated by osteoblasts. Modification enhanced adhesiveness of osteoblastic cells;the results indicated synergic action of the combined use of PLGA or PLGA/CAG on the growth of osteoblasts. There were no difference in MTT between the PLGA and PLGA/CAG composite groups. Osteoblasts in vitro had the same morphological feature as in vivo,secreted AKP and synthesised collagen type I too.2. All the animals survived from the operation and the incisions healed without special treatment. Results obtained from radiographic bone formation,histologic analysis and biomechanical testing indicated me materials stimulated bone formations differently. X-ray examination demonstrated that new bone formation in the defects received PLGA/CAG/rhBMP-2 were more abundant than the other groups. No significant difference in new bone formation between the PLGA/CAG and PLGA/CAG/VEGF composite groups at the 12th week after implantation (P>0.05),better than the PLGA and control groups. Defects received PLGA grafts reached insufficient repair,and defects received no graft got little bone formation. Biomechanical testing also demonstrated the same results. Biodegradation was observed in all of the implants,remnant were found in the defects 6th week after the operation. Conclusion:l.The PLGA,PLGA/CAG,PLGA/CAG/rhBMP-2 and PLGA/CAG/VEGF scaffolds were suitable for bone defects repairing.2. In vitro test suggested PLGA,PLGA/CAG have satisfactory biocompatibility and promoted the adhension of osteoblasts.3. MTT assay is a good method for measuring the osteoblast proliferation. The rat osteoblasts could be used to study the cytocompatibility of biomaterials related to bone graft substitutes.4. PLGA coated with Calcium Alginate gel (CAG) enhanced its biomechanics and optimizing the properties. The PLGA/CAG composite has good osteoconductibility and improve the quality of novel bone formation. A composite of PLGA / CAG was a new valuable implant material of bone.5. The foam of PLGA coated with alginate calcium was good carrier for rhBMP-2 or VEGF,has the better osteoinductive ability. It produced a notable effect with regard to velocity,quantity and quality of bone formation.
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