Synthesis, characterization and bioactivity evaluation of nano-structured hydroxyapatite

Abstract

Due to its biocompatibility and bioactivity, hydroxyapatite (HA) has a wide range of applications in medical engineering cases, such as bone repair and bone tissue regeneration. The use of artificial HA with a similar structure and chemical composition to biological apatite could increase the durability of the HA inside the natural hard tissues. The aim of the present work was to synthesis nano-structured HA via different routs, the comparison of their characteristics and enhancement of the bioactivity of HA by controlling its crystallite size and chemical composition. Nano HA was prepared by mechanical activation and sol gel routs. The x-ray diffraction technique (XRD), Fourier transform infra red spectroscopy (FTIR) and transmission electron microscopy (TEM) were used to characterize the HA powder. The synthesized powder was soaked in simulated body fluid (SBF) for various periods of time in order to evaluate its bioresorbability and bioactivity after immersion in SBF. Atomic absorption spectroscopy (AAS) was used to determine the dissolution of calcium ions in the SBF media. Results showed that the prepared HA powder had a nanoscale structure with a size of 29 nm for the powder prepared by mechanical activation and 25 nm for the powder that was prepared by the sol gel method. The ionic dissolution rate of nano-structured powder was higher than conventional HA (with micro scale size) and was similar to biological apatite. It could be concluded that bioactivity behaviour of HA powder is affected by its crystallite size. Using the nano-structured HA powder with less than 50 nm crystallite size, the optimum bioactivity and bioresorbability would be achieved.