Autogenous bone grafts are widely used in the repair of bone defects. Growth factors such as bone morphogenetic protein 2 (BMP-2) can induce bone regeneration and enhance bone growth. The combination of an autogenous bone graft and BMP-2 may provide a better osteogenic effect than either treatment alone, but BMP-2 is easily inactivated in body fluid. The objective of this study was to develop a technique that can better preserve the in vivo activity of BMP-2 incorporated in bone grafts. In this study, we first prepared BMP-2/poly(lactic-co-glycolic acid) (PLGA) delayed-release microspheres, and then combined collagen, the delayed-release microspheres, and rat autologous bone particulates to form four groups of composite grafts with different combinations: collagen in group A; collagen combined with bone particulates in group B; collagen combined with BMP-2/PLGA delayed-release microspheres in group C; and collagen combined with both bone particulates and BMP-2/PLGA delayed-release microspheres in group D. The four groups of composite grafts were implanted into the gluteus maximus pockets in rats. The ectopic osteogenesis and ALP level in group D (experimental group) were compared with those in groups A, B, and C (control groups) to study whether it had higher osteogenic capability. Results showed that the composite graft design increased the utility of BMP-2 and reduced the required dose of BMP-2 and volume of autologous bone. The selection of bone particulate diameter had an impact on the osteogenetic potential of bone grafts. Collagen prevented the occurrence of aseptic inflammation and improved the osteoinductivity of BMP-2. These results showed that this composite graft design is effective and feasible for use in bone repair.

The aim of this study was to develop a superior bone engineering material for repair of bone defects. A composite of calcium polyphosphate fiber (CPPF)/calcium phosphate cement (CPC)/micromorselized bone was prepared. A scanning electron microscope was used to observe the structure of the composite and measure its porosity. Seventy-two pieces of the material were placed in phosphate buffer solution and changes in pH were measured over time, and compressive strength was also measured. In vivo experiments were carried out on 72 rabbits divided into six groups: bone implantation with CPPF/CPC/micromorselized bone, CPC/micromorselized bone, micromorselized bone, CPPF/CPC, CPC, respectively; and no implantation (control). The implants were assessed with X-ray film and histologically, and bone density and biomechanical strength were measured. The study period was 12 weeks. The addition of CPPF increased apertures of the composite. The bone defects in the CPPF/CPC/micromorselized group compared with the other groups had significantly higher radiographic grading and significantly greater bone density (p < 0.05) and biomechanical strength (p < 0.05). The new composite improves the speed and quality of bone formation. The addition of CPPF improved the mechanical properties of the scaffold material and created higher porosity.