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The problem of acoustic feedback in hearing aids could be solved potentially by applying a compliant hydrogel to the outer surface that would conform to the ear canal and block feedback. With this objective, several formulations of hydrogels were developed and their swelling and mechanical properties investigated. Hydrogel formulations were polymerized from hydroxyethyl methacrylate (HEMA) and N-vinyl-pyrrolidone (NVP), with various photo-initiators, crosslinkers, and swelling agents. The hydrogel that swelled most rapidly and yet remained undissolved in water had a monomer composition of 40 mol% HEMA, 60 mol% NVP, with 1 wt% polyethylene glycol dimethacrylate as a crosslinker, and 0.5 wt% 2,2-dimethoxy-2-phenyl-acetophenone as the photo-initiator. The tensile modulus, strength, hardness, and durability of the dry hydrogels were not a strong function of composition. In the swollen state, the mechanical properties were much reduced. The potential use of these materials on hearing aids has been discussed in this article. [ABSTRACT FROM AUTHOR]

Microbial infections on implanted medical devices are difficult to treat. Application of 70 kHz ultrasonic irradiation to gentamicin treatment greatly enhanced the action of the antibiotic in terms of reduced viable bacterial concentrations. Ultrasonic irradiation was carried out at various insonation intensities that were noninhibitory in the absence of antibiotic. Synergistic killing was observed to be a function of ultrasonic intensity. Greatest killing (approximately 5 log reduction in viable population) was realized at full intensity (4.5 W/cm2), and decreased with reductions in power density. At lowest intensity (10 mW/cm2), no significant acoustic enhanced killing was noted.

Extended wear soft contact lenses have been implicated in the increased occurrence of corneal bacterial infections. This research investigated the effects of polymer chemistry, water content, and pre-sorbed proteins upon the adherence of Pseudomonas aeruginosa to model hydrogels with chemistries similar to those of extended wear soft contact lenses. The hydrogels were exposed to washed suspensions of P. aeruginosa in a laminar flow cell. Albumin, fibrinogen, desialylated fibrinogen, or mucin were deposited on the hydrogels before exposure to the bacteria. Results showed that with or without protein pre-exposure, bacterial adhesion decreased as water content increased. In the presence of the sorbed protein, the number of adherent bacteria increased by about 45%, and all four proteins caused similar increases in adhesion. Bacterial adhesion was not significantly influenced by the presence of sialic acid residues in the pre-sorbed protein.