Recent advances in research applications of nanophase hydroxyapatite

Hydroxyapatite, the main inorganic material in natural bone, has been used widely for orthopaedic applications. Due to size effects and surface phenomena at the nanoscale, nanophase hydroxyapatite possesses unique properties compared to its bulk-phase counterpart. The high surface-to-volume ratio, reactivities, and biomimetic morphologies make nano-hydroxyapatite more favourable in applications such as orthopaedic implant coating or bone substitute filler. Recently, more efforts have been focused on the possibility of combining hydroxyapatite with other drugs and materials for multipurpose applications, such as antimicrobial treatments, osteoporosis treatments and magnetic manipulation. To build more effective nano-hydroxyapatite and composite systems, the particle synthesis processes, chemistry, and toxicity have to be thoroughly investigated. In this Minireview, we report the recent advances in research regarding nano-hydroxyapatite. Synthesis routes and a wide range of applications of hydroxyapatite nanoparticles will be discussed. The Minireview also addresses several challenges concerning the biosafety of the nanoparticles. Biocompatible nanomaterials: Nano-hydroxyapatite materials combine the benefits of nanosized particles with the main organic phase of bone, hydroxyapatite. The advantages of nano-hydroxyapatite are biocompatibility, controlled delivery and capacity to couple with hydrophobic materials. This Minireview discusses the syntheses of nano-hydroxyapatite materials and their applications in the fields of hard tissue repair, drug delivery, antibacterial treatments, magnetic delivery and gene therapy.