The Preparation of Nanostructured Hydroxyapatite in Organic Solvents for Clinical Applications

Composite materials consisting of Hydroxyapatite (HAP) nano-crystals and biocompatible polymers have been widely used in orthopedic and dental application. These composite can provide both ease of use and superior mechanical properties of polymers, osteoconductivity and bioactivity of HAP. The formation of HAP in different organic solvents and water was investigated to fabricate such composites at moderate temperatures. HAP nano-sized crystals with high degree of crystallinity were formed at room temperature by rapid addition of (NH 4 ) 2 HPO 4 solution into Ca(NO 3 ) 2 .4H 2 O solution, filtration and subsequent drying at 40 oC. The effect of different organic solvents, addition mode and temperature on the characteristics of HAP was examined. The HAP powders were characterized using Fourier transform infrared spectrometer (FTIR), X-ray diffraction (XRD), and Transmission electron microscopy (TEM). The HAP crystal shape was governed by the type of solvent: fine regular spheres and rods were formed from organic solvents with lower dielectric constants while irregular particles were prepared using water with higher dielectric constant. The synthesized HAP rod crystals were between (20-100) nm length and (2-6) nm thickness. All the FTIR and XRD profiles of HAP fabricated from ethanol were in good agreement with the FTIR and XRD spectrums of commercial HAP. It is therefore feasible to fabricate HAP uniform nano-particles in organic solvents at room temperature, which would be of benefit for the fabrication of polymer-HAP composites for biomedical applications.