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Physiological silicon incorporation into bone mineral requires orthosilicic acid metabolism to SiO44.

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Chappell, Helen F 
Jugdaohsingh, Ravin  ORCID logo
Powell, Jonathan J 


Under physiological conditions, the predominant form of bioavailable silicon (Si) is orthosilicic acid (OSA). In this study, given Si's recognized positive effect on bone growth and integrity, we examined the chemical form and position of this natural Si source in the inorganic bone mineral hydroxyapatite (HA). X-ray diffraction (XRD) of rat tibia bone mineral showed that the mineral phase was similar to that of phase-pure HA. However, theoretical XRD patterns revealed that at the levels found in bone, the 'Si effect' would be virtually undetectable. Thus we used first principles density functional theory calculations to explore the energetic and geometric consequences of substituting OSA into a large HA model. Formation energy analysis revealed that OSA is not favourable as a neutral interstitial substitution but can be incorporated as a silicate ion substituting for a phosphate ion, suggesting that incorporation will only occur under specific conditions at the bone-remodelling interface and that dietary forms of Si will be metabolized to simpler chemical forms, specifically [Formula: see text]. Furthermore, we show that this substitution, at the low silicate concentrations found in the biological environment, is likely to be a driver of calcium phosphate crystallization from an amorphous to a fully mineralized state.



bone structure, mineralization drivers, orthosilicic acid, silicon, Animals, Bone and Bones, Durapatite, Rats, Silicates, Silicon, X-Ray Diffraction

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J R Soc Interface

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The Royal Society


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Medical Research Council (MR/R005699/1)
HC would like to thank the UK Medical Research Council (Grant number U105960399) for their support and award of a Career Development Fellowship at MRC-HNR. RJ and JJP would like to also acknowledge the MRC for support (Grant number MR/R005699/1).