Bioactive strong biodegradable bone cement for rapid osteointegration and osteogenesis

Polymethyl methacrylate (PMMA) bone cement is one of the most successful biomaterials in orthopaedic fixation, however, the poor osteogenic/osteointegration and high exothermic temperature limited their wide applications especially the complex clinical bone diseases. In this study, a multifunctional bioactive bone cement reinforced with the poly(citrate-silicon) (PCS) nanospheres was developed for overcoming the limitation of PMMA bone cement (PMMA-PCS). Compared with traditional PMMA, PMMA-PCS cement showed the increased injectability (about 5.56 times), extended setting time (about 6.4 min), increased hydrophilicity (46.9 degrees) and reduced polymerization heat (about 41.9 degrees C), without affecting the stability and plasticity. The mechanical strength was also more matched to the bone, with a compression modulus of about 61.8% of PMMA, which was beneficial for reducing stress concentration at the bone implantation site. PMMA-PCS bone cement also had good degradability, with a degradation rate of about 34.79% in 6 weeks. PMMA-PCS bone cement possessed the antioxidant, in vitro fluorescence imaging, in vitro antibacterial, and in vitro biomineralization properties. The cellular experiments showed that PMMA-PCS bone cement showed the improved osteogenic differentiation, mineral deposition, good anti-inflammatory and pro-angiogenic properties. In a rat femoral condyle defect model, the results demonstrated that PMMA-PCS bone cement could significantly promote the new bone formation and bone ingrowth both at the cement-bone contact surface and inside the cement, through improving the osteogenic proteins and angiogenesis.