Properties and cytotoxicity of water soluble Na2O–CaO–P2O5 glasses

Various compositions of Na2O–CaO–P2O5 glasses are prepared to estimate glass formation, dissolution properties and cytotoxicity. In the wide composition range of 40 mol% of P2O5 or more, clear glass samples were obtained. The estimated glass forming region was consistent with other ternary phosphate glass systems. The glass transition temperatures and crystallization temperatures decreased with increasing P2O5 content and increased with CaO content. Dissolution properties in distilled water and simulated body fluid (SBF) were measured. In distilled water, CaO free glasses showed extremely fast dissolution. The dissolution rate decreased with increasing CaO content and decreasing P2O5 content. This composition effect results from cross-link formation between the non-bridging oxygens of two different chains by Ca2+ ions which improves the phosphate network strength. In SBF, the dissolution rate followed a similar trend, but glass dissolution was suppressed. This suppression occurred due to the existence of soluble species of glass such as Na+, Ca2+ and HPO2-4. The cytotoxicity decreased with increasing CaO content and with decreasing PO2.5 content. This was the result of a change in pH and ion concentration in the medium.