Zinc containing bioactive glasses with ultra-high crystallization temperature, good biological performance and antibacterial effects

Novel bioactive glasses with different amount of zinc oxide (ZnO), namely 2, 3.8 and 5 mol%, were designed, produced by a melt-quenching route and investigated in terms of biological performance. Proper amounts of ZnO were added to a previously developed bioactive glass containing strontium and magnesium, characterized by an ultra-high crystallization temperature. Thus, the aim of the work was to obtain a bioactive glass with high crystallization temperature in view of an eventual thermal treatment, as well as antibacterial properties (due to the antimicrobial effect of zinc, as reported in the literature). Bioactivity was investigated by immersion in Simulated Body Fluid (SBF), which is a commonly used protocol to evaluate samples' bioactivity in vitro. Additionally, in order to exclude the possible cytotoxicity of Zn containing bioactive glasses, a biological investigation using MLO-Y4 cells was carried out, both by direct (NR uptake) and indirect (MTT) contact tests. Finally, the antibacterial effects of the produced bioactive glasses against Staphylococcus epidermidis (Gram-positive), Pseudomonas aeruginosa and Escherichia coli (both Gram-negative) were investigated.