Adhesion of yeasts and bacteria to fluoro-alkylsiloxane layers chemisorbed on silicone rubber

Indwelling voice prostheses are most often made of silicone rubber. However, the silicone rubber surface attracts huge quantities of adhering yeasts and bacteria and their colonization on the valve side of voice prostheses leads to frequent malfunctioning. On average, indwelling voice prostheses have to be replaced every three to four months. In this paper, we report on the in vitro adhesion of yeasts and bacteria to fluoro-alkylsiloxane layers chemisorbed on silicone rubber surfaces, as measured in a parallel plate flow chamber. Silicone rubber surfaces were first oxidized with an argon plasma treatment (Ar-SR). In a second step, organic layers were created by chemisorption of fluoroalkyltrichlorosilanes onto the Ar-SR surfaces, denoted as Ar-SR-CF3 and Ar-SR-C8F17, respectively. Physico-chemical properties of the chemisorbed layers were studied by using water contact angle measurements, X-ray photoelectron spectroscopy (XPS) and attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR). Using a parallel plate flow chamber, adhesion of Streptococcus salivarius, Staphylococcus epidermidis, Candida albicans and Candida tropicalis strains, isolated from explanted voice prostheses, was investigated to the chemisorbed fluoroalkylsiloxane layers with and without a salivary conditioning film. Ar-SR-CF3 and Ar-SR-C8F17 surfaces showed significantly reduced microbial adhesion as compared to original silicone rubber, both with respect to initial deposition rates and adhesion in a stationary end-point. Furthermore, adhering microorganisms were more easily detached when applying an air-liquid interface. Silicone rubber surfaces with chemisorbed, long fluorocarbon chains (Ar-SR-C8F17) showed the greatest reduction in microbial adhesion, probably because of their low surface free energy combined with a higher surface mobility. (C) 1998 Elsevier Science B.V

A new method for in vivo evaluation of biofilms on surface-modified silicone rubber voice prostheses

A new method is presented that permits a rapid and accurate in vivo evaluation of biofilm formation on surface-modified silicone rubber voice prostheses. The method is based on partial modification of a Groningen button voice prosthesis by exposing half of the prosthesis to an argon plasma. This results in one side of the prosthesis becoming hydrophilic while leaving the unmodified side hydrophobic as a control. Modified prostheses were placed in patients for an evaluation period of approximately 4 weeks. Despite making the silicone rubber surface hydrophilic, biofilm formation was stimulated when compared to unmodified, hydrophobic silicone rubber. Findings show that biofilm formation on voice prostheses is influenced by hydrophobicity of a silicone rubber surface. The method of partial surface modification used was seen to be suitable for demonstrating such influences regardless of nutrition and other variations in the patient's lifestyle. Microbiological analysis of the biofilms on both sides of the prosthesis valve did not show any changes in microbial composition, with Candida albicans, streptococci and staphylococci being the most commonly isolated strains