Preparation and characterization of antibacterial P2O5-CaO-Na2O-Ag2O glasses

60P(2)O(5)-20CaO-(20 - x) Na2O-xAg(2)O and 60P(2)O(5)-30CaO-(10 - x) Na2O-xAg(2)O glasses, x = 0, 0.5,1, and 2 mol % were prepared using normal glass melting technique. The antibacterial activity of pressed disks of powdered glass (undoped and silver-doped glass) was investigated against S. aureus, P. aeruginosa, and E. coli micro-organisms using agar disk-diffusion assays at 37 degrees C for 24 h. The antibacterial activity was deduced from the inhibition zone diameter (IZD), zone of no bacterial growth, measured under the stated experimental conditions. The antibacterial activity increases with the increase in IZD and vice versa. Dissolution of glass in water at 37 degrees C, pH changes of water during glass dissolution, and concentrations of silver ions released from silver-doped glasses into water during their dissolution were determined. An increase in the concentration of silver ions released from silver-doped glasses into water was observed with increasing time of glass dissolution and with increasing Ag2O content. The tested silver-free and silver-doped glasses demonstrated different antibacterial activity against the tested micro-organisms. For silver-free glasses, an increase in IZD was observed with the increase in the glass dissolution rate and with the decrease in pH of water. Also, the IZD showed an increase with increasing Ag2O content of silver-doped glasses. (C) 2011 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 98A: 132-142, 2011.