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 P(2)O(5) 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 T(g) 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% P(2)O(5) precipitated a calcium bridged trimetaphosphate (Na(4)Ca[PO(3)](6)) at the sodium oxide contents of 25 and 20 mol%, but at the 15 mol% level two phases formed, NaCa[PO(3)](3) and Ca(2)P(2)O(7). The 50 mol% P(2)O(5) compositions showed two sodium phosphate-rich phases [NaCa(PO(3))(3) and NaPO(3)] for the lower calcium containing compositions, and a calcium phosphate phase [CaP(2)O(6)] for compositions with higher CaO mol%. The 55 mol% P(2)O(5) compositions, exhibited similar phases for the lower calcium containing compositions, and a single calcium phosphate phase (CaP(2)O(6)) was identified for the higher calcium containing composition. NMR analysis revealed the presence of Q(1) and Q(2) species in the 45 mol% P(2)O(5) compositions, and Q(2) species present in the 50 and 55 mol% P(2)O(5) compositions. The non-linear data obtained from the thermal and solubility analyses conducted were attributed to the packing density of the 45 mol% P(2)O(5) 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 Ca(2+) ions into solution. (C) 2003 Elsevier Ltd. All rights reserved.