Bioactive glasses 70SiO₂-(30-x)CaO-xZnO (x=1, 3, 5 mol.%) were prepared by the acid-free hydrothermal method in keeping with the green chemical technology. The synthetic glasses were investigated by TG-DSC, BET, XRD, and SEM-EDX. All synthetic glasses present mesoporous structures consisting of aggregates of nano-particles. The bioactivity of synthetic glasses was confirmed through the formation of the hydroxyapatite phase after in vitro experiment in the SBF solution. The effect of Zn addition is shown through the decrease in the bioactivity of synthetic glasses. Additionally, the ICP-OES analysis indicates that the Zn contents were completely released from the glassy networks after 5 days of immersion. The in vitro experiment in cell culture matter was performed for osteoblast cells SaOS₂. The results confirmed the biocompatibility of synthetic glasses and the role of Zn addition in the proliferation of living cells.