Preparation of Calcium Phosphate/Polyurethane Composite Porous Scaffolds for Bone Repair by in situ Self-foaming Method

One of the main technical problems in preparation of calcium phosphate/polyurethane (CaP/PU) compos- ite scaffold for bone repair is to obtain a porous structure with uniformly distributed pores. The reason for this is due to the heterogeneous dispersion of the added foaming agents within the composite resulting in the increasing viscosity of polymer precursor during the composite fabrication process. To solve this problem, we report a novel method through incorporation of calcium hydrogen phosphate (DCPD) with polymer phase to achieve a composite system in early period of the synthesis process of CaP/PU composite. The uniformly distributed crystal water from DCPD can be released when temperature reaches above 75 ℃ and serve as foaming agents to react with isocyanate group in the PU and generate CO2 gas. The generation of gas leads to a self-foaming process and consequently in- duces CaP/PU composite to form a porous scaffold. Scanning electron microscopy (SEM) observations show that CaP/PU composite scaffolds with uniform porous structure, high porosity and interconnectivity were obtained at 90 ℃. The mechanical strength can be doubled by re-curing treatment for the scaffold at 110 ℃ for 24 h. The re- sulting CaP/PU composite scaffolds with uniformly porous structure, high porosity and interconnectivity have shown potential applications in bone tissue engineering. Moreover, this simple and efficient method may provide new approaches for the preparation of polyurethane- based porous scaffolds.