Thorough analysis of silicon substitution in biphasic calcium phosphate bioceramics: A multi-technique study

S Gomes,E Jallot,F Babonneau,J.-M Nedelec,G Renaudin,A Mesbah,C Bonhomme

doi:10.1016/j.actbio.2010.02.034

Abstract

Four samples of composition Ca(10)(PO(4))(6-x)(SiO(4))(x)(OH)(2-x), with x=0.0, 0.1, 0.2 and 0.5, were prepared and characterized using powder X-ray and neutron powder diffraction, and (1)H, (31)P and (29)Si nuclear magnetic resonance (NMR) spectroscopy. The composition of the Si-substituted HAp phases was determined by joint Rietveld refinements from powder X-ray and powder neutron diffraction data. Taking into account electroneutrality, a chemical formula for the Si-substituted HAp phases with indication of the incorporated silicate amount is proposed. Solid-state (29)Si NMR confirms the presence of only Q(0) species, in good agreement with the presence of substituted HAp and beta-TCP phases only. Thanks to NMR spectroscopy, two types of protons in the Si-substituted HAp phase were identified, the new site corresponding to species engaged in hydrogen bonding with silicate anions. This allowed further refinement of the formulae for these phases with very good quantitative agreement for populations derived from the refinement and integration of NMR data.

Highlights

Biphasic calcium phosphate (BCP) ceramics, composed of a mixture of hydroxyapatite (HAp, Ca10(PO4)6(OH)2) and b-tricalcium phosphate (b-TCP, b-Ca3(PO4)2), are interesting candidates in reconstructive surgery
Bone mineral mass is dominated by nanocrystalline multisubstituted calcium phosphate apatite [1,2,3]
The type and amount of ionic substitutions in the apatite phase of bone vary from the weight per cent level to the parts per million level

Summary

Introduction

Biphasic calcium phosphate (BCP) ceramics, composed of a mixture of hydroxyapatite (HAp, Ca10(PO4)6(OH)2) and b-tricalcium phosphate (b-TCP, b-Ca3(PO4)2), are interesting candidates in reconstructive surgery. Bone mineral mass is dominated by nanocrystalline multisubstituted calcium phosphate apatite [1,2,3]. The type and amount of ionic substitutions in the apatite phase of bone vary from the weight per cent (wt.%) level (for carbonate substitution [4]) to the parts per million (ppm) level (for strontium or barium substitutions, for example [5]). The role of many of these ionic species in hard tissues is not fully understood owing to the difficulties encountered in monitoring and quantifying their amounts, which vary according to dietary alteration, and to physiological and pathological causes [6]. HAp is widely used as a biomaterial in clinical applications

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