In vivo evaluation of injectable calcium phosphate cement composed of Zn- and Si-incorporated β-tricalcium phosphate and monocalcium phosphate monohydrate for a critical sized defect of the rabbit femoral condyle.

Zinc (Zn) enhances bone formation with mineralization and is an essential element of osteoblastic proliferation. Silicon (Si) is important in apatite formation coupled with the promotion of osteogenesis. The primary focus of this work was the assessment of the bone healing capacity of calcium phosphate cements (CPC) composed of Zn- and Si-incorporated β-tri calcium phosphate (TCP) and mono calcium phosphate mono hydrate (MCPM). Zn- and Si-incorporated β-TCP was synthesized through a sol gel process with varying amounts of Zn: (3, 6, or 9% w/w) and 15% w/w Si. Fabricated CPC samples were characterized by scanning electron microscopy, setting time, injectability, compressive strength and initial pH change with time. Compositional analysis and the effects of Zn and Si on cellular interaction were evaluated by energy dispersive X-ray spectroscopy mapping, viability determination and F-actin assay. The data were used to optimize the CPC formulation. The efficacy of bone healing was investigated via implantation into critical sized rabbit femoral condyle defects for 4 and 8 weeks. CPC cement with 6% (w/w) Zn content was the best candidate for faster bone healing (bone to tibial volume ratio in 8 weeks: 22.78% ± 0.02). Significantly faster degradation was also revealed. Bone healing was significantly delayed when CPC cement with 9% (w/w) Zn was used.