ABSTRACT
BACKGROUND: Nowadays complex bone defects have become a great challenge to orthopedists. A synergistic contribution of various growth factors and a crosstalk between their signaling pathways have been suggested as determinatives for the overall osteogenic outcome.OBJECTIVE: To develop calcium phosphate cement (CPC) incorporated with γ-polyglutamic acid/carboxymethyl chitosan (PGA/CMCS), and to evaluate its physical and chemical properties and sustained-release function. METHODS: The γ-PGA/CMCS polymer composites were prepared by graft copolymerization and spray freeze drying methods, and then loaded with recombinant human bone morphogenetic protein 2 (rhBMP-2) growth factor. CPC served as control group, and γ-PGA/CMCS-CPC containing different contents of rhBMP-2 as experimental groups. A γ-PGA/CMCS-CPC scaffold with regular blade-like crystalline structure was fabricated by injection compression molding. Before mixed with the liquid phase, the solid additives were properly mixed by wet method of CPC solid and the γ-PGA/CMCS carrier, then the pre-blended mix was freeze-dried. The setting time and compressive strength of bone cement in each group were detected, and the microstructure of the material surface was observed under scanning electron microscopy. In vitro release of rhBMP-2 was investigated. The effect of bone cement extracts on cell proliferation was determined through MTS assay.RESULTS AND CONCLUSION: γ-PGA/CMCS-CPC had the same physicochemical properties to the CPC. Initial and final setting time, compressive strength of bone cement had no significant differences among groups. The scanning electron microscope results showed that the γ-PGA/CMCS-CPC scaffold was covered by regular blade-like crystalline structure and the γ-PGA/CMCS particles were uniformly dispersed in the CPC crystals. A sustained release of rhBMP-2 was observed from the γ-PGA/CMCS-CPC. The cell experiments exhibited that the samples with regular blade-like crystalline structure had better cell response compared to CPC control groups with irregular crystalline structure. These findings indicate that γ-PGA/CMCS-CPC can maintain good physicochemical properties, and release growth factor or drug to promote bone formation.