The influence of local structure and surface morphology on the antibacterial activity of silver-containing calcium borosilicate glasses

A silver containing series of glasses starting from Ag-free 1.5B2O3·SiO·CaO parent glass and ending with 3mol% Ag2O was synthesized by the conventional melt quenching method and analyzed in order to correlate the composition and the structural peculiarities with the antibacterial effects. The structure and surface morphology of samples were characterized by X-ray diffraction (XRD), infrared (FTIR) and Raman spectroscopy, Scanning Electron Microscopy (SEM). X-ray photoelectron spectroscopy (XPS) was used to determine the nature of chemical bonding and the surface composition of the samples. The results indicate that all samples are vitreous and their local structure — mainly built by tetrahedral (BØ4‐), triangular (BØ3 and BØ2O−) borate species (Ø representing an oxygen atom bridging two boron atoms) and silicate Q1, Q2, Q3 units — is reactive to the silver oxide addition. Based on XPS data, both Ag+ and Ag0 ions are present on the surface of detected silver nanoparticles. Ag nanoparticles (AgNPs) embbeded in glasses were evaluated for their antimicrobial activity against the gram-positive and gram-negative bacteria, i.e. Staphylococcus aureus and Escherichia coli bacteria. The antibacterial effect of investigated samples increases simultaneously with the Ag2O content and AgNP dimension. The proposed mechanism is discussed in relation with the local structure, Ag+/Ag0 ratio and AgNP dimensions. •Melt-derived Ag2O–B2O3–SiO2–CaO bioactive glasses (x≤3mol%)•Silver influence on short range order, surface composition and morphology•Ag nanoparticles (AgNPs) developed on sample surface.•Antibacterial effect depends both on Ag2O content and sample structure.•Antibacterial effect increases with AgNPs dimension.