Broad-spectrum bactericidal activity of Ag2O-doped bioactive glass

Bioactive glass has found extensive application as an orthopedic and dental graft material and most recently also as a tissue engineering scaffold. Here we report an initial investigation of the in vitro antibacterial properties of AgBG, a novel bioactive glass composition doped with Ag2O. The bacteriostatic and bactericidal properties of this new material and of two other bioactive glass compositions, 45S5 Bioglass and BG, have been studied by using Escherichia coli, Pseudomonas aeruginosa, and Staphylococcus aureus as test microorganisms. Concentrations of AgBG in the range of 0.05 to 0.20 mg of AgBG per ml of culture medium were found to inhibit the growth of these bacteria. Not only was AgBG bacteriostatic, but it also elicited a rapid bactericidal action. A complete bactericidal effect was elicited within the first hours of incubation at AgBG concentrations of 10 mg ml(-1). 45S5 Bioglass and BG had no effect on bacterial growth or viability. The antibacterial action of AgBG is attributed exclusively to the leaching of Ag+ ions from the glass matrix. Analytical measurements rule out any contribution to AgBG-mediated bacterial killing by changes in pH or ionic strength or the dissolution of other ionic species from the biomaterials. Our observations of the dissolution profiles of Ag+ from AgBG in the presence and absence of bacteria are consistent with silver accumulation by the bacteria.