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°) and reduced polymerization heat (about 41.9℃), 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.