Novel injectable and self-setting composite materials for bone defect repair

Although calcium sulfate bone cements possess favorable characteristics of excellent clinical handling and osteoconductivity, the rapid degradation and poor bioactivity limit their wide applications. This study reports a type of novel injectable and self-setting composite materials for bone defect repair. Magnesium substituted tricalcium phosphate nanoparticles (43.8±9.0 nm) and calcium sulfate hemihydrate micro-size particles (5–21 µm) were mixed with a polyvinyl alcohol solution with optimal compositions to obtain the composite materials, which showed reasonable initial setting time (11.7–19.2 min) and suitable compressed strength (2.28–6.33 MPa). By utilizing magnesium powder as a porogen, macro-pores (>100 µm) together with micro-pores were created in the final product after setting. In addition, MC3T3E1 cells extended well and exhibited numerous lamellipodia and long filopodia when cultured with the composite materials, indicating that they had no cytotoxicity. The in vivo results indicated that the injectable composite materials could achieve bone defect repair, when implanted in beagle femoral condyle defects for 10 months. Our results show that the new injectable composite materials are biocompatible and biodegradable, which possess great potential for bone defect repair.