Advancements in hydroxyapatite synthesis and surface modifications for emerging biomedical applications

This review provides a comprehensive examination of advancements in hydroxyapatite (HA) synthesis, surface modifications, and emerging applications across various biomedical domains. This paper begins with an introduction and history of the fundamental composition and significance of HA in biomedical research, detailing the objectives and structure of this review. It then focuses on HA synthesis techniques, exploring traditional methods and innovative strategies that derive HA from natural resources, such as eggshells, animal bones, and marine sources. The discussion also highlights enhancements in the controlled synthesis under mild conditions, revealing the evolution of fabrication methods. The objectives of HA surface modification are provided and relevant techniques, such as silanisation, polymer grafting, and amino acid grafting, to enhance the efficacy of biomedical applications, are introduced. The impact of these techniques on HA performance was analysed, focusing on substituted forms, such as multi-substituted, sodium, and magnesium, compared with pure HA. The perspectives identified obstacles inhibiting the widespread acceptance of HAs, identified gaps in current knowledge, and predicted future developments in HA applications. These findings indicate that HAs possess significant potential to enhance existing biomedical interventions and pioneer innovative approaches in the healthcare sector.