Phosphate glasses for tissue engineering: Part 1. Processing and characterisation of a ternary-based P2O5-CaO-Na2O glass system.
This paper presents the results of a study of the thermal properties, X-ray powder diffraction (XRPD), NMR and solubility of a range of phosphate-based glasses. Ion release and pH measurements were also obtained. The compositions were limited by fixing the P2O5 mol% content at 45, 50 and 55 mol%, and varying the CaO mol% at 30, 35 and 40 mol%. Initial data collected from thermal analysis showed an increase in the Tg values, with increasing CaO mol%, as expected. An increase in crystallisation temperatures with increasing CaO mol% was also observed, with sharp peaks indicating the presence of single and/or double phases. Initial XRPD data revealed that the 45 mol% P2O5 precipitated a calcium bridged trimetaphosphate (Na4Ca[PO3]6) at the sodium oxide contents of 25 and 20 mol%, but at the 15 mol% level two phases formed, NaCa[PO3]3 and Ca2P2O7. The 50 mol% P2O5 compositions showed two sodium phosphate-rich phases [NaCa(PO3)3 and NaPO3] for the lower calcium containing compositions, and a calcium phosphate phase [CaP2O6] for compositions with higher CaO mol%. The 55 mol% P2O5 compositions, exhibited similar phases for the lower calcium containing compositions, and a single calcium phosphate phase (CaP2O6) was identified for the higher calcium containing composition. NMR analysis revealed the presence of Q1 and Q2 species in the 45 mol% P2O5 compositions, and Q2 species present in the 50 and 55 mol% P2O5 compositions. The non-linear data obtained from the thermal and solubility analyses conducted were attributed to the packing density of the 45 mol% P2O5 compositions. The solubility was seen to decrease with increasing CaO mol%, for all the glasses investigated, and all the compositions showed a gradual decrease in pH with time, and this was accounted for by the release of Na+ and Ca2+ ions into solution.
Department of Biomaterials and Tissue Engineering, Eastman Dental Institute, University College London, 256 Gray's Inn Road, London WC1X 8LD, UK.
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Ahmed
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Lewis
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Olsen
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Knowles
D001672:Biocompatible Materials / Q000737:chemistry; D002118:Calcium / Q000737:chemistry; D002130:Calcium Phosphates / Q000737:chemistry; D005898:Glass / Q000737:chemistry; D006863:Hydrogen-Ion Concentration; D007477:Ions; D009682:Magnetic Resonance Spectroscopy; D010087:Oxides / Q000737:chemistry; D010710:Phosphates / Q000737:chemistry* / Q000494:pharmacology; D017680:Potassium Compounds / Q000737:chemistry; D012964:Sodium / Q000737:chemistry; D017670:Sodium Compounds / Q000737:chemistry; D012995:Solubility; D013696:Temperature; D013997:Time Factors; D023822:Tissue Engineering / Q000379:methods*; D014961:X-Ray Diffraction
D001672:Biocompatible Materials; D002130:Calcium Phosphates; D007477:Ions; D010087:Oxides; D010710:Phosphates; D017680:Potassium Compounds; D017670:Sodium Compounds; C096707:sodium oxide; C068440:potassium oxide; C020243:calcium phosphate; D012964:Sodium; C018279:sodium phosphate; D002118:Calcium