Mechanical properties and cytocompatibility of poly(ε-caprolactone)-infiltrated biphasic calcium phosphate scaffolds with bimodal pore distribution

Biphasic calcium phosphate scaffolds have attracted interest because they have good osteoconductivity and a resorption rate close to that of new bone ingrowth, but their brittleness limits their potential applications. In this study, we show how the infiltration of biphasic calcium phosphate scaffolds with poly(ε-caprolactone) improves their mechanical properties. It was found that the polymer effectively contributes to energy to failure enhancement in bending, compressive and tensile tests. The main toughening mechanism in these composites is crack bridging by polymer fibrils. The presence of fibrils at two different size scales – as found in scaffolds with a bimodal pore distribution – results in a more effective toughening effect as compared to scaffolds with a monomodal pore size distribution, especially in the early stage of mechanical deformation. An optimized infiltration process allowed the preservation of micropore interconnection after infiltration, which is beneficial for cells adhesion. In addition, it is shown that biphasic calcium phosphates infiltrated with poly(ε-caprolactone) are cytocompatible with human bone marrow stromal cells, which makes them good candidates for bone substitution.