Silver zeolite-loaded silicone elastomers: a multidisciplinary approach to synthesis and antimicrobial assessment

Abstract

A multidisciplinary approach has been applied to the preparation of antibacterial Ag zeolite/silicone elastomer composites aimed at products that satisfy a range of requirements, namely good mechanical properties after zeolite incorporation and strongly antibacterial. Zeolite X was synthesised and used as antibacterial agent after ion-exchange with silver. The high level of silver (14 wt%) within the zeolite enabled the preparation of antibacterial composites containing a relatively low level of zeolite (2 wt%). The composites showed strong efficacy against Escherichia coli and Staphylococcus epidermidis. Organic functionalization of the zeolite with organo-silanes prior blending with the matrix usefully improved composite mechanical properties and reduced color development in Ag zeolite containing silicone elastomers. Organo-silane modification did not substantially affect the antibacterial performance of the materials; the number of viable cells of both Gram-positive and Gram-negative bacteria was reduced to beyond detection limits within 24 hours of incubation. Efficacy of the Ag zeolite containing composites against the yeast Candida albicans was found to be substantially less than observed with the two bacteria. This study demonstrates that evaluation of polymer composites needs to be performed via a multidisciplinary approach in order to avoid compromising a particular aspect of the materials' design, characteristics or performance, including the use of reliable testing methods to determine the latter.