Mechanism of incorporation of zinc into hydroxyapatite

Abstract

The atomic level mechanism of incorporation of Zn(2+) into hydroxyapatite (HAp), which is a potential dopant to promote bone formation, was investigated, based on first principles total energy calculations and experimental X-ray absorption near edge structure (XANES) analyses. It was found that Zn(2+)-doped HAp tends to have a Ca-deficient chemical composition and substitutional Zn(2+) ions are associated with a defect complex with a Ca(2+) vacancy and two charge compensating protons. Moreover, first principles calculations demonstrated that Zn(2+) incorporation into HAp can take place by occupying the Ca(2+) vacancy of the defect complex. The Ca(2+) vacancy complex is not only the origin of the calcium deficiency in HAp, but also plays a key role in the uptake of trace elements during mineralization.

Fine structure study on low concentration zinc substituted hydroxyapatite nanoparticles

“…The X-ray absorption fine structure (XAFS) technique is very useful to analyze the local coordination environment of the substituted atoms. The XAFS results prove that Zn 2+ inside HAP has a single coordination environment and the coordination number is close to 4 [24]. It is suggested that zinc favors to substitute in the Ca2 site over the Ca1 site in HAP according to DFT modeling [22].…”

Structural and morphological analysis of zinc incorporated non-stoichiometric hydroxyapatite nano powders

“…The chemical composition of nHAp is complicated in reality, however the general chemical formula can be presented as formula given in the equation (1) [9]. (1) Precipitated or synthetic hydroxyapatite (sHAp) and calcium deficient hydroxyapatite (CDHAp) are also categorized as Non-Stoichiometric Hydroxyapatite due to formation of vacancies or incorporation of foreign cations or anions in the atomic structure of HAp [10,11].…”

Preparation and characterization of Mg-doped fluorapatite nanopowders by sol–gel method

“…F − , CO3 2− , Na + , Mg +2 , Zn +2 ) are present in biological apatites [8]. Properties of HA, such as bioactivity, biocompatibility, solubility, and adsorption properties can be tailored over a wide range by modifying the composition via ionic substitutions [9,10].…”