Synthesis and characterization of silver/silicon-cosubstituted nanohydroxyapatite

Favorable cell-material interaction and the absence of undesirable reaction from the host body defence system play a critical role in determining the success and long-term survival of the implants. Substitution of various elements into hydroxyapatite (HA) has been done to alter its chemical composition, thereby mimicking that of the bone mineral. In this study, a cosubstituted nanosized apatite (Ag/Si-HA) containing Ag (0.3 wt %) and Si (0.8 wt %) was synthesized by an aqueous precipitation technique. The synthesized Ag/Si-HA displayed a rod-like morphology of dimensions ~50 nm in length and ~15 nm in width, as observed from the transmission electron microscope image. With an increase in temperature, the aspect ratio of nanosized Ag/Si-HA decreased, whilst the size increased. Autoclaving was used to achieve sufficient crystallinity while maintaining the rod-like morphology and size that were comparable to that of the bone apatite. A pure Ag/Si-HA was produced without any undesirable secondary phases, as evidenced from the X-ray diffraction and thermal gravimetric results. The Ag/Si cosubstitution affected the lattice cell parameters, in particularly the a- and c- axes which further led to an expansion of the unit cell volume. In addition, the relative intensity of the hydroxyl vibrational bands was reduced. These results demonstrated that a stable phase-pure Ag/Si-HA was produced using an aqueous precipitation reaction.