Layer-by-layer deposition of antimicrobial silver nanoparticles on textile fibers

Antimicrobial silver nanoparticles were immobilized on nylon and silk fibers by following the layer-by-layer deposition method. The sequential dipping of nylon or silk fibers in dilute solutions of poly(diallyldimethylammonium chloride) (PDADMAC) and silver nanoparticles capped with poly(methacrylic acid) (PMA) led to the formation of a colored thin film possessing antimicrobial properties. The layer-by-layer deposition was monitored by measuring the K/S value, which is the ratio between the sorption coefficient (K) and the scattering (S) of the coated fibers, with a reflectance spectrophotometer. The K/S values for both silk and nylon fibers were found to increase as a function of the number of deposited layers. Although the film growth was observed on both fibers, the K/S value of the nylon fiber was significantly lower than silk fibers. Scanning electron microscopy studies of both fibers confirmed that the layer-by-layer coating on the nylon fibers was not as uniform as on the silk fibers. Antimicrobial tests against Staphylococcus aureus bacteria were performed and antimicrobial activity was demonstrated for both coated fibers. The deposition of 20 PDADMAC/PMAcapAg layers onto the fibers resulted in 80% bacteria reduction for the silk fiber and 50% for the nylon fiber. Although the film growth was more efficient on the silk fibers, these results suggest that this technique could be used in the design of new synthetic or natural technical fibers where antimicrobial properties are required. (c) 2006 Elsevier B.V. All rights reserved.