2. Case Study: Hydroxyapatite–Titanium Bulk Composites for Bone Tissue Engineering Applications

The research on bulk hydroxyapatite (HA)-based composites is driven by the need to develop biomaterials with better mechanical properties without compromising biocompatibility properties. Despite several years of research, the mechanical properties of the HA-based composites still need to be enhanced to match the properties of natural cortical bone. In this regard, the scope of the present chapter is limited to discuss the processing and the mechanical as well as biocompatibility properties in the context of bone tissue engineering applications of a model system i.e. HA–Ti. It will be discussed as how hydroxyapatite-titanium (HA–Ti) based bulk composites can be processed to have better fracture toughness and strength together with uncompromised biocompatibility. On the materials fabrication aspect, the recent results are discussed to demonstrate that advanced manufacturing technique like, spark plasma sintering can be adopted as an advanced processing route to restrict the sintering reactions, while enhancing the mechanical properties. Various toughening mechanisms are discussed with an emphasis to synergize multiple toughening mechanisms, which requires careful tailoring of microstructure. The in vitro cytocompatibilty, as well as in vivo biocompatibility results are also reviewed.