Effect of silver content on the structure and antibacterial activity of silver-doped phosphate-based glasses

Valappil, Sabeel P. and Pickup, David M. and Carroll, Donna L. and Hope, Chris and Pratten, Jonathan and Newport, Robert J. and Smith, Mark E. and Wilson, Michael and Knowles, Jonathan C. (2007) Effect of silver content on the structure and antibacterial activity of silver-doped phosphate-based glasses. Antimicrobial Agents and Chemotherapy, 51 (12). pp. 4453-4461. ISSN 0066-4804. (Full text available)

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http://dx.doi.org/10.1128/AAC.00605-07

Abstract

Staphylococcus aureus can cause a range of diseases, such as osteomyellitis, as well as colonize implanted medical devices. In most instances the organism forms biofilms that not only are resistant to the body's defense mechanisms but also display decreased susceptibilities to antibiotics. In the present study, we have examined the effect of increasing silver contents in phosphate-based glasses to prevent the formation of S. aureus biofilms. Silver was found to be an effective bactericidal agent against S. aureus biofilms, and the rate of silver ion release (0.42 to 1.22 mu g.mm(-2).h(-1)) from phosphate-based glass was found to account for the variation in its bactericidal effect. Analysis of biofilms by confocal microscopy indicated that they consisted of an upper layer of viable bacteria together with a layer (similar to 20 mu m) of nonviable cells on the glass surface. Our results showed that regardless of the silver contents in these glasses (10, 15, or 20 mol%) the silver exists in its +1 oxidation state, which is known to be a highly effective bactericidal agent compared to that of silver in other oxidation states (+2 or +3). Analysis of the glasses by P-31 nuclear magnetic resonance imaging and high-energy X-ray diffraction showed that it is the structural rearrangement of the phosphate network that is responsible for the variation in silver ion release and the associated bactericidal effectiveness. Thus, an understanding of the glass structure is important in interpreting the in vitro data and also has important clinical implications for the potential use of the phosphate-based glasses in orthopedic applications to deliver silver ions to combat S. aureus biofilm infections.

Item Type: Article
Subjects: Q Science > Q Science (General)
Divisions: Faculties > Science Technology and Medical Studies > School of Physical Sciences > Functional Materials Group
Depositing User: Bob Newport
Date Deposited: 16 Jul 2008 18:47
Last Modified: 03 Jun 2014 15:10
Resource URI: http://kar.kent.ac.uk/id/eprint/8234 (The current URI for this page, for reference purposes)
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