title: Synthesis, characterization and modelling of zinc and silicate co-substituted hydroxyapatite.
abstract: 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.
authors.affiliation: Department of Materials Science and Metallurgy, University of Cambridge, 27 Charles Babbage Road, Cambridge CB3 0FS, UK robert.friederichs@gmail.com.
authors.forename: Robert J
authors.identifier: http://orcid.org/0000-0002-6778-1927
authors.initials: RJ
authors.lastname: Friederichs
authors.affiliation: Department of Archaeology and Anthropology, University of Cambridge, Downing Street, Cambridge CB2 3DZ, UK MRC Human Nutrition Research, 120 Fulborn Road, Cambridge CB1 9NL, UK.
authors.forename: Helen F
authors.initials: HF
authors.lastname: Chappell
authors.affiliation: Department of Materials Science and Metallurgy, University of Cambridge, 27 Charles Babbage Road, Cambridge CB3 0FS, UK.
authors.forename: David V
authors.initials: DV
authors.lastname: Shepherd
authors.affiliation: Department of Materials Science and Metallurgy, University of Cambridge, 27 Charles Babbage Road, Cambridge CB3 0FS, UK.
authors.forename: Serena M
authors.initials: SM
authors.lastname: Best
mesh_terms: D017886:Durapatite / Q000138:chemical synthesis* / Q000737:chemistry*; D006358:Hot Temperature; D008956:Models, Chemical; D017640:Silicates / Q000737:chemistry*; D015032:Zinc / Q000737:chemistry*
chemical_list: D017640:Silicates; D017886:Durapatite; D015032:Zinc
keywords: calcium phosphate; hydroxyapatite; modelling; silicate; silicon; zinc