Multifunctional Hydroxyapatite: Recent Progress and Future Prospects in Biomedicine and Materials Science

Abstract

One of the most studied biomaterials for biomedical applications is hydroxyapatite (HAp), a bioactive ceramic (Ca-P) with structural and compositional similarity to the mineral phase of human bones and teeth. HAp is investigated for various applications, such as bone regeneration, dental implants, tissue engineering, implant coatings, and controlled drug delivery systems, due to its excellent biocompatibility, osteoconductivity, and ability to accommodate ionic substitutions. This review accounts for an extensive overview of crystal chemistry, structure–property relationship, mechanical properties, and biological activity of HAp. The focus is given to the effect of ionic substitutions, microstructural characteristics, and processing parameters on the physicochemical and biomedical behavior of HAp-based materials. The review also covers the latest developments on composite biomaterials, additive manufacturing, multifunctional coatings, and nanostructured HAp systems for future healthcare applications. Furthermore, a processing–structure–property–performance (PSPP) framework is suggested for setting up correlations between material design, functional properties, and clinical performance. In addition, challenges in mechanical reliability, long-term stability, and clinical translation are discussed. Finally, future research directions for smart biomaterials, artificial intelligence-aided materials design, and patient-specific regenerative therapies are highlighted. This review aims to offer an integrated view of advanced HAp-based biomaterials for regenerative medicine and personalized health care.