Sol-gel coatings which elute bioactive silver ions are presented as a potential solution to the problem of biofilm formation on indwelling surfaces. There is evidence that high-temperature processing of such materials can lead to diffusion of silver away from the coating surface, reducing the amount of available silver. In this study, we report the biofilm inhibition of a Staphylococcus epidermidis biofilm using a low-temperature processed silver-doped phenyltriethoxysilane sol-gel coating. The incorporation of a silver salt into a sol-gel matrix resulted in an initial high release of silver in de-ionised water and physiological buffered saline (PBS), followed by a lower sustained release for at least 6 days-as determined by graphite furnace-atomic absorption spectroscopy (GF-AAS). The release of silver ions from the sol-gel coating reduced the adhesion and prevented formation of a S. epidermidis biofilm over a 10-day period. The presence of surface silver before and after 24 h immersion in PBS was confirmed by X-ray photoelectron spectroscopy (XPS). These silver-doped coatings also exhibited significant antibacterial activity against planktonic S. epidermidis. A simple test to visualise the antibacterial effect of silver release coatings on neighbouring bacterial cultures is also reported. r

Silver nanoparticles (AgNPs) were synthesised by reducing silver salts using NaBH 4 followed by capping with varying concentrations of -cyclodextrin (-CD) and were physically characterised. Antibacterial activity against Escherichia coli, Pseudomonas aeruginosa and Staphylococcus aureus was determined by a microtitre well method.The AgNPs were spherical under transmission electron microscopy, whilst dynamic light scattering showed average diameters of capped particles to be smaller (4-7 nm) than their uncapped equivalents (17 nm). Capped particles demonstrated superior photostability when exposed to intense ultraviolet radiation for 4 h as well as significantly (P < 0.05) higher (up to 3.5-fold) antibacterial activity. The influence of -CD concentration was seen to delay bacterial growth, indicating that a Trojan horse mechanism may be occurring owing to bacterial carbohydrate affinity, thereby enhancing silver ion absorption.

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