One-dimensional hydroxyapatite materials: preparation and applications

As one of the biominerals, hydroxyapatite (HAP) plays important roles in biology, and inspires researchers to investigate HAP-based materials for the applications in various biomedical fields. Among them, one-dimensional (1-D) micro-/nanostructured HAP materials have attracted great interest in the last decades. This review summarizes the preparation and applications of 1-D HAP materials, and discusses different aspects of 1-D HAP materials. Various synthetic methods have been developed to prepare 1-D HAP materials with different morphologies, sizes, surface properties and crystallinities. In addition, elements-substituted 1-D HAP materials and composites have also been prepared. Surfactants and additives are usually adopted to control the nucleation and growth of 1-D HAP materials, but the related mechanisms are not very clear yet. The applications of 1-D HAP materials have been widely investigated, and the biomedical applications show great prospect but still need further improvements. A new kind of highly flexible fire-resistant inorganic paper made of ultralong HAP nanowires has been developed and is a promising alternative of the traditional cellulose paper for valuable archives and important documents. Regardless of the advances, further studies should be made for preparing 1-D HAP materials with controlled structures, sizes and morphologies and for boosting their various applications.