Study on the preparation and properties of silver-doped phosphate antibacterial glasses (Part I)

Silver-doped phosphate antibacterial glasses were prepared by the melting method. The antibacterial effects of some undoped and silver–doped glasses of compositions 65P2O5–10CaO–(25–x) Na2O, 70P2O5–20CaO–(10–x) Na2Oand (70–x) P2O5–30CaO, (where x = 0, 0.5, 1.2 Ag2O), against Staphylococcus aureus, Pseudomonas aeruginosa and Escherichia coli micro-organisms using agar disk-diffusion assays were investigated. The structures of some glasses were studied by XRD, FT-IR, and UV–VIS spectroscopy. The variation of pH with dissolution rate was studied. The tested silver-free and silver-doped glasses demonstrated different antibacterial effects against the tested micro-organisms. For silver-free glasses, an increase in inhibition zone diameter (zone of no bacterial growth) was seen with the decrease in water pH. Silver-doped glasses showed an increase in inhibition zone diameter with increasing Ag2O content. The low pH produced by glass dissolution was certainly a critical factor for glass antibacterial effect. The more the phosphate ions released the lower is the pH and the greater the antibacterial effect.

Graphical abstractPhotos of Petri dishes after conducting agar disk-diffusion assays at 37 °C for 24 h with (a) S. aureus, (b) P. aeruginosa and (c) E. coli as test micro-organisms. (For glasses containing 2 mol % Ag2O).Figure optionsDownload full-size imageDownload as PowerPoint slide