Broad-Spectrum Bactericidal Activity of Ag ₂ O-Doped Bioactive Glass

Abstract

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 Ag 2 O. 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.Bioactive glasses are special glass systems which are generally composed of SiO 2 , CaO, P 2 O 5 , and Na 2 O. They can be produced by the traditional melting process or by the more versatile sol-gel process (14, 15). The bioactive behavior of these glasses is defined as the ability to bond to soft and hard tissues by means of a series of reactions, which produces a strong, compliant interface between the glass and the tissue (14). Due to their high level of tissue integration and regeneration (15, 34), bioactive glasses have been used clinically in a variety of situations. Bioactive glass devices are now available to treat conductive deafness and alveolar ridge resorption and bone loss due to periodontal disease and to fill cystic and surgically created defects, particularly in craniomaxillofacial sites (19,25,33).The material under investigation in the present work is a novel bioactive glass system composed of SiO 2 , CaO, P 2 O 5 , and Ag 2 O. The introduction of Ag 2 O into the bioactive glass composition is aimed at minimizing the risk of microbial contamination through the potential antimicrobial activity of the leaching Ag ϩ ions (7, 13). The introduction of silver has recently become one of the preferred methods to confer microbial resiliency on biomedical materials and devices (1,6,17,18,21), since the incidence of biomaterial-centered infections is one of the main causes of revision surgery (12). The production of the material via the sol-gel process allows the tailoring of the textural characteristics of the matrix in order to obtain a controlled Ag ϩ delivery system. Here we report an initial investigation of ...

Twenty-first century challenges for biomaterials

“…Localized control of bacteria and inflammation that lead to cellular de-differentiation is needed. The in vitro bioactivity and antibacterial action of a novel sol-gel-derived glass, AgBG, in the system SiO 2 -CaO -P 2 O 5 -Ag 2 O offer a new twenty-first century biomaterials approach towards solving these problems Bellantone et al , 2002Blaker et al 2004;Saravanapavan et al 2004;Lohbauer et al 2005a,b;Jones et al 2006c). The incorporation of 3 wt% Ag 2 O in the bioactive gel glass system confers antimicrobial properties to the glass without compromising its bioactivity.…”

Bioactive glass and glass-ceramic scaffolds for bone tissue engineering

“…Further studies using 45S5 Bioglass ® particles have shown encouraging results regarding potential angiogenic effects of Bioglass ® , i.e., increased secretion of vascular endothelial growth factor (VEGF) and VEGF gene expression in vitro, as well as enhancement of vascularization in vivo [53][54][55][56] (see §4). In addition, the incorporation of particular ions into the silicate network, such as silver [20][21][22] and boron [26,27], has been investigated in order 6 to develop antibacterial and antimicrobial materials. Bioactive glasses can also serve as vehicle for the local delivery of selected ions being able to control specific cell functions [30,[57][58][59][60][61][62][63][64].…”

“…The high amounts of Na 2 O and CaO, as well as the relatively high CaO/P 2 O 5 ratio make the glass surface highly reactive in physiological environments [11]. Other bioactive glass compositions developed over the years contain no sodium or have additional elements incorporated in the silicate network such as fluorine [13], magnesium [14,15], strontium [16][17][18], iron [19], silver [20][21][22][23], boron [24][25][26][27], potassium [28] or zinc [29,30]. Fabrication techniques for bioactive glasses include both traditional melting methods and sol-gel techniques [1, 3,4,10,[31][32][33], the latter are being highlighted elsewhere [34] and are not covered in this review.…”

Photocatalytic Antibacterial Effect of TiO2 Film of TiAg on Streptococcus mutans

“…5,9 Recently, Ag has attracted attention, and now it is widely used in medical materials owing to its antibacterial effects. 10 Therefore, it was hypothesized that a TiO 2 coating formed on a Titanium silver (TiAg) alloy might exhibit superior antibacterial activity against oral microorganisms to that formed on a Ti substrate alone.…”