Novel continuous flow synthesis, characterization and antibacterial studies of nanoscale zinc substituted hydroxyapatite bioceramics

Abstract

Calcium phosphates predominantly hydroxyapatite (HA) has extensively been used as bone substitute material and as coatings on metallic implants because of its high biocompatibility and bioactivity in bone mineralization. In order to enhance bioactivity of HA, hydroxyapatite has been substituted with divalent cations and anions. In this research, zinc substituted hydroxyapatite powder (<100nm) was synthesized from aqueous solution of calcium nitrate tetrahydrate (with different concentration of Zn ions) and diammonium hydrogen phosphate in the presence of ammonium hydroxide solution through a novel continuous plastic flow synthesis (CPFS) at 70°C in 5min residence time at pH 11. The obtained powders were physically characterized using transmission electron microscopy (TEM), Scanning electron microscopy (SEM), BET surface area analysis, X-ray powder diffraction analysis (XRD), and FTIR and Raman spectroscopy. In addition, the particle size was evaluated by Dynamic light scattering (DLS). The chemical structural analysis of all as prepared samples was done using X-ray photoelectron spectroscopy (XPS).The present study showed that all nanoscale particulates had rod like morphology (at low Zn concentration), which changed to semispherical morphology with increasing Zn contents. It was also investigated that zinc substituted hydroxyapatite gave better antibacterial protection than pure HA. Thus, the CPFS system facilitated rapid production of high surface area nanoscale crystals of hydroxyapatite modified by Zn ions with controlled particle properties (crystallinity, size, shape) at (near) ambient conditions.