Synthesis and release of trace elements from hollow and porous hydroxyapatite spheres

Abstract

It is known that organic species regulate fabrication of hierarchical biological forms viasolution methods. However, in this study, we observed that the presence of inorganic ionsplays an important role in the formation and regulation of biological sphericalhydroxyapatite formation. We present a mineralization method to prepare ion-dopedhydroxyapatite spheres with a hierarchical structure that is free of organic surfactants andbiological additives. Porous and hollow strontium-doped hydroxyapatite spheres weresynthesized via controlling the concentration of strontium ions in a calcium and phosphatebuffer solution. Similarly, fluoride and silicon-doped hydroxyapatite spheres weresynthesized. While spherical particle formation was attainable at low and high temperaturefor Sr-doped hydroxyapatite, it was only possible at high temperature in theF/Si-doped system. The presence of inorganic ions not only plays an importantrole in the formation and regulation of biological spherical hydroxyapatite, butalso could introduce pharmaceutical effects as a result of trace element release.Such ion release results showed a sustained release with pH responsive behavior,and significantly influenced the hydroxyapatite re-precipitation. These ion-dopedhydroxyapatite spheres with hollow and porous structure could have promising applicationsas bone/tooth materials, drug delivery systems, and chromatography supports.