Influence of partial replacing of CaO by SrO on structure and bioactivity of calcium-phospho-silicate glasses

New alkali-free bioglasses of the ternary 60SiO2 center dot 5P2O5 center dot 35CaO parent glass wherein Ca is partially substituted by Sr (up to 10 mol%) were prepared by sol-gel method. The replacement of Ca with Sr induced the tendency to crystallisation of an apatite type phase. The bioactivity tested in vitro depends on Ca/Sr replacement degree, despite the fact that the theoretical network connectivity does not change with Ca/Sr substitution. After seven days of incubation in simulated body fluid, only on the samples with x >= 5 mol% SrO was developed a layer assumed of combined Ca/Sr composition of carbonated hydroxyapatite. Bactericidal activity was observed exclusively in case of strontium containing samples, for both Gram positive and negative bacteria. Structural effects of partial replacing of CaO by SrO were investigated by X-ray diffraction and FTIR analysis both before and after samples incubation in simulated body fluid.