Glass surfaces were modified by end-grafting poly(ethylene oxide) (PEO) chains having molecular weights of 526, 2000, or 9800 Da. Characterization using water contact angles, ellipsometry, and X-ray photoelectron spectroscopy confirmed the presence of the PEO brushes on the surface with estimated lengths in water of 2.8-, 7.5-, and 23.7-nm, respectively. Adhesion of two bacterial (Staphylococcus epidermidis and Pseudomonas aeruginosa) and two yeast (Candida albicans and Candida tropicalis) strains to these brushes was studied and compared to their adhesion to bare glass. For the bacterium P. aeruginosa and the yeast C. tropicalis, adhesion to the 2.8-nm brush was comparable to their adhesion on bare glass, whereas adhesion to the 7.5- and 23.7-nm brushes was greatly reduced. For S. epidermidis, adhesion was only slightly higher to the 2.8-nm brush than that to the longer brushes. Adhesion of the yeast C. albicans to the PEO brushes was lower than that to glass, but no differences in adhesion were found between the three brush lengths. After passage of an air bubble, nearly all microorganisms adhering to a brush were removed, irrespective of brush length, whereas retention of the adhering organisms on glass was much higher. No significant differences were found in adhesion nor retention between experiments conducted at 20 and those conducted at 37 degrees C.

Aims: The effects and extent of adhesion of four different bacterial and two yeast strains isolated from explanted voice prostheses to silicone rubber with and without an adsorbed rhamnolipid biosurfactant layer obtained from Pseudomonas aeruginosa DS10-129 was studied. Methods and Results: The ability of rhamnolipid biosurfactant to inhibit adhesion of micro-organisms to silicone rubber was investigated in a parallel-plate flow chamber. The anti-adhesive activity of the biosurfactant at different concentrations was significant against all the strains and depended on the micro-organism tested. The results showed an effective reduction in the initial deposition rates, and the number of bacterial cells adhering after 4 h, for all micro-organisms tested at the 4 g l )1 undiluted rhamnolipid solution. Maximum initial reduction of adhesion rate (an average of 66%) occurred for Streptococcus salivarius GB 24/9 and Candida tropicalis GB 9/9. The number of cells adhering after 4 h on silicone rubber conditioned with biosurfactant was reduced to 48% for Staphylococcus epidermidis GB 9/6, Strep. salivarius GB 24/9, Staphylococcus aureus GB 2/1 and C. tropicalis GB 9/9 in comparison to controls. Perfusing the flow chamber with biosurfactant containing solution followed by the passage of a liquid-air interface, to investigate detachment of micro-organisms adhering to silicone rubber, produced high detachment (96%) of adhered cells for all microorganisms studied, except for Staph. aureus GB 2/1 (67%). Significance and Impact of the Study: It is concluded that biosurfactant represent suitable compounds that should be considered in developing future strategies to prevent the microbial colonization of silicone rubber voice prostheses. is uncomfortable, costly, time consuming and may lead to damage of the shunt with scar tissue formation, insufficiency or stenosis. Less frequent replacements of voice prosthesis therefore would be advantageous and has resulted in general interest in finding techniques to inhibit biofilm formation and prolonging the lifetime of voice prostheses Elving et al. 2000; Rodrigues et al. 2004a,b). Everaert et al. (1999) studied, in vivo, the influence of perfluoroalkylsiloxane (PA) surface modification of silicone rubber voice prostheses on biofouling, with 18 consecutive patients with laryngectomies, and found that chemisorption of long-chain PAs reduces biofilm formation. Additionally, Rodrigues et al. (2004a) developed a promising strategy to lengthen lifetime of the voice prostheses as it was demonstrating that the use of biosurfactants obtained from probiotic bacteria inhibit biofilm formation and the occurrence of increased airflow resistances.Surfactants of microbial origin, referred to as biosurfactants, are surface-active compounds that have some influence on interfaces. With regard to an anti-adhesive effect of biosurfactants, hypotheses have been forwarded in which adsorption of biosurfactants to a substratum surface alters the hydrophobicity of the surface and causes interference in m...

Micron-sized particles adhering to collector surfaces can be detached by passing a liquid−air interface over the adhering particles. Theoretically, the efficiency of particle detachment depends on the interface velocity, the liquid surface tension, the viscosity, and the particle−substratum interaction forces. In this study we perfuse an air bubble through a parallel-plate flow chamber to study detachment of polystyrene particles from a quartz collector surface, at different interface velocities and liquid surface tensions and upon multiple air bubble passages. A linear relation was found between particle removal and the liquid−air interface velocity, with negligible removal at elevated velocities. Linear relations were also found between particle removal and the liquid−air surface tensions, with different slopes for different air bubble velocities. Particle removal could be increased by the passage of multiple air bubbles. In summary, this study shows that liquid−air interfaces can be employed to detach micron-sized particles from collector surfaces. The detachment process can be optimized by adjusting the air bubble velocities, the surface tensions, and the number of bubbles applied.