Nano-hydroxyapatite for use in bone tissue repair

Abstract

Bone can be considered as a biological hybrid material composed of organic and inorganic components: collagen and rod-shaped hydroxyapatite (HAP) of 20–50 nm lengths. The synthetic hydroxyapatite (Ca10(PO4)6(OH)2) has been extensively used as a bone substitute material due to its chemical and structural similarities with natural mineral bone. One way to obtain HAP nanoparticles is by using self-assembled amphiphilic molecules as structure directors. This study involves different hexadecyltrimethylammonium bromide (CTAB) micellar-block copolymer organized networks. Inorganic precursors were added in sequence to the CTAB-polymer solution, followed by a hydrothermal treatment. The final product was separated from the suspension by filtration and then dried. The X-ray diffraction and infrared spectroscopy pattern of the materials synthesized corresponds to the HAP pattern. Transmission and scanning electron microscopy microphotographs show a fiber network composed by 37 nm length HAP nanorods. After treatment with simulated body fluid (SBF) a layer of HAP nanocrystals grew on the material surface; that is related to the bioactivity of the material. To confirm the samples' biocompatibility, calvarial osteoblasts obtained from neonatal rats were exposed to the material and then, viability and cell adhesion were evaluated. A new method of HAP nanocrystals with similar shape, morphology and chemical characteristics of bone were developed. After SBF immersion, material revealed a spherulitic-like HAP layer that implies a positive physiological response and good bond ability to the host tissue. Therefore, nanomaterials obtained by the proposed synthesis could have a wide range of biomedical applications.