Synthesis, characterization and modelling of zinc and silicate co-substituted hydroxyapatite.

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Friederichs, Robert J  ORCID logo
Chappell, Helen F 
Shepherd, David V 
Best, Serena M 

Experimental chemistry and atomic modelling studies were performed here to investigate a novel ionic co-substitution in hydroxyapatite (HA). Zinc, silicate co-substituted HA (ZnSiHA) remained phase pure after heating to 1100 °C with Zn and Si amounts of 0.6 wt% and 1.2 wt%, respectively. Unique lattice expansions in ZnSiHA, silicate Fourier transform infrared peaks and changes to the hydroxyl IR stretching region suggested Zn and silicate co-substitution in ZnSiHA. Zn and silicate insertion into HA was modelled using density functional theory (DFT). Different scenarios were considered where Zn substituted for different calcium sites or at a 2b site along the c-axis, which was suspected in singly substituted ZnHA. The most energetically favourable site in ZnSiHA was Zn positioned at a previously unreported interstitial site just off the c-axis near a silicate tetrahedron sitting on a phosphate site. A combination of experimental chemistry and DFT modelling provided insight into these complex co-substituted calcium phosphates that could find biomedical application as a synthetic bone mineral substitute.

calcium phosphate, hydroxyapatite, modelling, silicate, silicon, zinc, Durapatite, Hot Temperature, Models, Chemical, Silicates, Zinc
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J R Soc Interface
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The Royal Society
This work was supported by a NSFGRFP grant (DGE-1042796) (RJF) and a Cambridge International Scholarship (RJF). The modelling work was performed using the Darwin Supercomputer of the University of Cambridge High Performance Computing Service (, provided by Dell Inc. using Strategic Research Infrastructure Funding from the Higher Education Funding Council for England and funding from the Science and Technology Facilities Council. HC would like to thank the UK Medical Research Council (Grant number U105960399) for their support.