Strontium substituted bioactive glasses for tissue engineered scaffolds: the importance of octacalcium phosphate

Porous bioactive glasses are attractive for use as bone scaffolds. There is increasing interest in strontium containing bone grafts, since strontium ions are known to up-regulate osteoblasts and down regulate osteoclasts. This paper investigates the influence of partial to full substitution of stron...

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Main Authors:	Sriranganathan, Danujan, Kanwal, Nasima, Hing, Karin A., Hill, Robert G.
Format:	Online
Language:	English
Published:	Springer US 2015
Online Access:	https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4690837/

id	pubmed-4690837
recordtype	oai_dc
spelling	pubmed-46908372015-12-31 Strontium substituted bioactive glasses for tissue engineered scaffolds: the importance of octacalcium phosphate Sriranganathan, Danujan Kanwal, Nasima Hing, Karin A. Hill, Robert G. Biomaterials Synthesis and Characterization Porous bioactive glasses are attractive for use as bone scaffolds. There is increasing interest in strontium containing bone grafts, since strontium ions are known to up-regulate osteoblasts and down regulate osteoclasts. This paper investigates the influence of partial to full substitution of strontium for calcium on the dissolution and phase formation of a multicomponent high phosphate content bioactive glass. The glasses were synthesised by a high temperature melt quench route and ground to a powder of <38 microns. The dissolution of this powder and its ability to form apatite like phases after immersion in Tris buffer (pH 7.4) and simulated body fluid (SBF) was followed by inductively coupled plasma optical emission spectroscopy (ICP), Fourier transform infra red spectroscopy (FTIR), X-ray powder diffraction (XRD) and 31P solid state nuclear magnetic resonance spectroscopy up to 42 days of immersion. ICP indicated that all three glasses dissolved at approximately the same rate. The all calcium (SP-0Sr-35Ca) glass showed evidence of apatite like phase formation in both Tris buffer and SBF, as demonstrated after 3 days by FTIR and XRD analysis of the precipitate that formed during the acellular dissolution bioactivity studies. The strontium substituted SP-17Sr-17Ca glass showed no clear evidence of apatite like phase formation in Tris, but evidence of an apatite like phase was observed after 7 days incubation in SBF. The SP-35Sr-0Ca glass formed a new crystalline phase termed “X Phase” in Tris buffer which FTIR indicated was a form of crystalline orthophosphate. The SP-35Sr-0Ca glass appeared to support apatite like phase formation in SBF by 28 days incubation. The results indicate that strontium substitution for calcium in high phosphate content bioactive glasses can retard apatite like phase formation. It is proposed that apatite formation with high phosphate bioactive glasses occurs via an octacalcium phosphate (OCP) precursor phase that subsequently transforms to apatite. The equivalent octa-strontium phosphate does not exist and consequently in the absence of calcium, apatite formation does not occur. The amount of strontium that can be substituted for calcium in OCP probably determines the amount of strontium in the final apatite phase and the speed with which it forms. Springer US 2015-12-24 2016 /pmc/articles/PMC4690837/ /pubmed/26704556 http://dx.doi.org/10.1007/s10856-015-5653-6 Text en © The Author(s) 2015 Open AccessThis article is distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made.
repository_type	Open Access Journal
institution_category	Foreign Institution
institution	US National Center for Biotechnology Information
building	NCBI PubMed
collection	Online Access
language	English
format	Online
author	Sriranganathan, Danujan Kanwal, Nasima Hing, Karin A. Hill, Robert G.
spellingShingle	Sriranganathan, Danujan Kanwal, Nasima Hing, Karin A. Hill, Robert G. Strontium substituted bioactive glasses for tissue engineered scaffolds: the importance of octacalcium phosphate
author_facet	Sriranganathan, Danujan Kanwal, Nasima Hing, Karin A. Hill, Robert G.
author_sort	Sriranganathan, Danujan
title	Strontium substituted bioactive glasses for tissue engineered scaffolds: the importance of octacalcium phosphate
title_short	Strontium substituted bioactive glasses for tissue engineered scaffolds: the importance of octacalcium phosphate
title_full	Strontium substituted bioactive glasses for tissue engineered scaffolds: the importance of octacalcium phosphate
title_fullStr	Strontium substituted bioactive glasses for tissue engineered scaffolds: the importance of octacalcium phosphate
title_full_unstemmed	Strontium substituted bioactive glasses for tissue engineered scaffolds: the importance of octacalcium phosphate
title_sort	strontium substituted bioactive glasses for tissue engineered scaffolds: the importance of octacalcium phosphate
description	Porous bioactive glasses are attractive for use as bone scaffolds. There is increasing interest in strontium containing bone grafts, since strontium ions are known to up-regulate osteoblasts and down regulate osteoclasts. This paper investigates the influence of partial to full substitution of strontium for calcium on the dissolution and phase formation of a multicomponent high phosphate content bioactive glass. The glasses were synthesised by a high temperature melt quench route and ground to a powder of <38 microns. The dissolution of this powder and its ability to form apatite like phases after immersion in Tris buffer (pH 7.4) and simulated body fluid (SBF) was followed by inductively coupled plasma optical emission spectroscopy (ICP), Fourier transform infra red spectroscopy (FTIR), X-ray powder diffraction (XRD) and 31P solid state nuclear magnetic resonance spectroscopy up to 42 days of immersion. ICP indicated that all three glasses dissolved at approximately the same rate. The all calcium (SP-0Sr-35Ca) glass showed evidence of apatite like phase formation in both Tris buffer and SBF, as demonstrated after 3 days by FTIR and XRD analysis of the precipitate that formed during the acellular dissolution bioactivity studies. The strontium substituted SP-17Sr-17Ca glass showed no clear evidence of apatite like phase formation in Tris, but evidence of an apatite like phase was observed after 7 days incubation in SBF. The SP-35Sr-0Ca glass formed a new crystalline phase termed “X Phase” in Tris buffer which FTIR indicated was a form of crystalline orthophosphate. The SP-35Sr-0Ca glass appeared to support apatite like phase formation in SBF by 28 days incubation. The results indicate that strontium substitution for calcium in high phosphate content bioactive glasses can retard apatite like phase formation. It is proposed that apatite formation with high phosphate bioactive glasses occurs via an octacalcium phosphate (OCP) precursor phase that subsequently transforms to apatite. The equivalent octa-strontium phosphate does not exist and consequently in the absence of calcium, apatite formation does not occur. The amount of strontium that can be substituted for calcium in OCP probably determines the amount of strontium in the final apatite phase and the speed with which it forms.
publisher	Springer US
publishDate	2015
url	https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4690837/
_version_	1613516639640223744

Strontium substituted bioactive glasses for tissue engineered scaffolds: the importance of octacalcium phosphate

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