Substance P incorporation in calcium phosphate cement for dental alveolar bone defect restoration

A combination of osteoinductive neuropeptide substance P (SP) and osteoconductive bone cement of calcium phosphate (CPC) might provide an effective and lower-cost solution for complex alveolar bone defects restoration. The present study aims to investigate the key design considerations of SP delivery in CPC. In this study, CPC-based modular scaffolds were developed, where collagen type I was used as accessory organic ingredient to modulate the physical and biological characters. SP was directly mixed in the cement as free peptides, or was covalently immobilized with collagen component. The structural and mechanical properties of the scaffolds were assessed in vitro, and their osteogenic ability was observed in a rabbit model with alveolar bone defect. The results showed that SP could enhance the osteo-conductivity/inductivity of CPC. Collagen solution optimized biocompatibility of CPC, and meanwhile exhibited additive effects on the functions of SP. Nevertheless, immobilization of SP with collagen blocked their bioactivity in CPC. Collagen sponges created macro-porosity in CPC and achieved maximum bone ingrowth with the aid of SP. In conclusion, the present study primarily demonstrated that CPC scaffold can be functionalized by synthetic SP, and the biocompatibility and porosity of the scaffold are adaptable key factors determining their final osteogenic activities.