Protein-based hydroxyapatite materials: tuning composition toward biomedical applications

Synthetic hydroxyapatite (HAp) has been successfully produced with the aim of obtaining biomaterials that meet the biomechanical requirements for bone tissue engineering, while being compatible with the surrounding biochemical and cellular environment. Combining proteins with HAp can generate improved composite biomaterials, which are environmentally friendly, renewable, and biocompatible. In this context, HAp/protein-based composite materials have been widely exploited since the late 20th century to the present day. In this review, we explore the biomedical relevance of the association of HAp with several proteins of interest such as fibroin, sericin, fibrin, and keratin. The processing strategies for their synthesis and effect on the obtained shape and physicochemical, mechanical, and biological performance are herein discussed. This work can provide useful information for the design of HAp-based biomaterials with specific emphasis on bone tissue regeneration characteristics for biomedical applications.