Na-Ca-phosphate glasses have been developed for a variety of biomedical applications, including fibers used in bio-composites [1]. More recently, Na-Ca-borate glasses have been developed for soft-tissue applications [2].  Phosphate glasses congruently dissolve in neutral aqueous environments by releasing metal cations and the long phosphate anions that constitute the glass structures, and the local pH that results can be acidic for glasses with greater phosphate concentrations [3]. Borate glasses also congruently dissolve to release metal cations and borate anions, and these glasses tend to increase the local pH [4].  In the present study, the structure and properties, including dissolution behavior, of several series of Na-Ca-borophosphate glasses will be described. The compositions were designed so that upon their dissolution, local pH’s varied from acidic to basic depending on the P₂O₅:B₂O₃ ratio.  Information about the constitution of the borophosphate glass network was obtained by MAS NMR, Raman, and High Performance Liquid Chromatography (HPLC) techniques, and Raman and HPLC analyses were also used to characterize the release of different anions from the glasses into aqueous environments. This information then will be used to explain the compositional dependence of glass properties, including the role played by tetrahedral borate units in a borophosphate network controlling the dissolution rates.

1.       J.C. Knowles, J. Mater. Chem., 13[10] 2395 (2003).

2.       M.N. Rahaman, D.E. day, et al., Acta Biomaterialia, 7[6] 2355 (2011).

3.       L. Ma, RK Brow, and ME Schlesinger, to be published Eur. J. Glass Sci. Tech., (2018).

4.       J.L. George and R.K. Brow, J. Non-Cryst. Solids, 426, 116 (2014).