Antimicrobial surface functionalization of plastic catheters by silver nanoparticles

Objectives: To test the antimicrobial activity and evaluate the risk of systemic toxicity of novel catheters coated with silver nanoparticles. Methods: Catheters were coated with silver using AgNO3, a surfactant and N,N,N ',N '-tetramethylethylenediamine as a reducing agent. Particle size was determined by electron microscopy. Silver release from the catheters was determined in vitro and in vivo using radioactive silver (Ag-110m(+)). Activity on microbial growth and biofilm formation was evaluated against pathogens most commonly involved in catheter-related infections, and the risk for systemic toxicity was estimated by measuring silver biodistribution in mice implanted subcutaneously with Ag-110m(+)-coated catheters. Results: The coating method yielded a thin (similar to 100 nm) layer of nanoparticles of silver on the surface of the catheters. Variations in AgNO3 concentration translated into proportional changes in silver coating (from 0.1 to 30 mu g/cm(2)). Sustained release of silver was demonstrated over a period of 10 days. Coated catheters showed significant in vitro antimicrobial activity and prevented biofilm formation using Escherichia coli, Enterococcus, Staphylococcus aureus, coagulase-negative staphylococci, Pseudomonas aeruginosa and Candida albicans. Approximately 15% of the coated silver eluted from the catheters in 10 days in vivo, with predominant excretion in faeces (8%), accumulation at the implantation site (3%) and no organ accumulation (<= 0.1%). Conclusions: A method to coat plastic catheters with bioactive silver nanoparticles was developed. These catheters are non-toxic and are capable of targeted and sustained release of silver at the implantation site. Because of their demonstrated antimicrobial properties, they may be useful in reducing the risk of infectious complications in patients with indwelling catheters.