Biphasic calcium phosphate scaffolds with controlled pore size distribution prepared by in-situ foaming

In this study, a reproducible method of fabricating hierarchically 3D porous scaffolds with high porosity and pore interconnectivity is reported. The method is based on in-situ foaming of a dispersion of diisocyanate, polyol, water and hydroxyapatite (HA) to form a hard foamed HA/polyurethane composite which after heat treatment provided a bi-phase calcium phosphate scaffold. This technique, combining the advantages of polymer sponge and direct foaming methods, provides a better control over the macrostructure of the scaffold. A modification of the multi-scaled porous macrostructure of scaffolds produced by changing the ratio of input reactants and by sintering temperature was studied. The pore morphology, size, and distribution were characterized using a scanning electron microscope and mercury porosimetry. The pores were open and interconnected with multi-scale (from several nanometres to millimetres) sizes convenient for using in tissue engineering applications. The bioactivity was confirmed by growing an apatite layer on the surfaces after immersion in simulated body fluid. The material was biocompatible, as shown by using normal human adipose tissue-derived stem cells (ASC). When seeded onto the scaffolds, the ASC adhered and remained healthy while maintaining their typical morphology.