Green synthesis of hydroxyapatite nanoparticles for biomedical application: a brief review

Hydroxyapatite [Ca10(PO4)6(OH)2] (HAp) is a calcium phosphate mineral of great interest in biomaterials development because it is the main component of the mineral phase of bones and teeth’s of animals and humans. HAp plays a key role in the biomedical field due to its non-toxicity, anti-inflammatory property, osteointegrity, biocompatibility, and other properties. Some of its applications in tissue engineering involve bone repair, bone augmentation, coating of implants, and fillers for bones and teeth. Besides, HAp can function as a drug delivery system due to its porous nature, which gives the nanoparticles a larger surface area. However, the use of organic templates in order to obtain HAp nanoparticles with a specific shape, morphology, size, and textural properties makes it impractical from an ecological and cost-effective standpoint. Throughout the last decade, several attempts to improve synthetic procedures have been under development. Recently, special attention has been given to the application of plant extracts as substitutes for organic templates, though they are not extensively reported in literature. Therefore, this brief review aims to examine the existing routes for synthesis of hydroxyapatite nanoparticles. Then the focus shifts to an overview of greener procedures and an outlook of their benefits in biomedical applications.