A Review on Synthesis, Characterisation, and Applications of Hydroxyapatite Nanoparticles

Due to its outstanding bioactivity and biocompatibility, hydroxyapatite (Ca10(PO4)6(OH)2, HAp) is a well-known biomaterial that has been extensively employed in clinical applications as tooth implants and bone substitutes. There are various methods to synthesise HAp. Some of them are chemical precipitation, hydrothermal, sol–gel method, etc. When it comes to calcium phosphate materials, HAP is the most stable phase. HAP has a significant ion exchange capacity and can be substituted by different numbers of ions in the crystal structure. Each substitution modifies the parameters of HAP's unit cell, which in turn modifies the material's crystallinity, thermal stability, structural stability, micromorphology, and other physicochemical and biological characteristics. Additionally, this broadens the applicability of HAP and offers fresh suggestions for its modification. This review work illustrates different synthesis methods employed for HAp. It also states how the pH and temperature, calcium sources, and reagents employed may affect the formation of different morphological structures of HAp. Results reveal that HAp has a great potential and can be used in many fields.