Washing resistant antibacterial composite coatings on cotton textiles

Several techniques have been developed to confer antibacterial properties to cotton textiles using silver nanoparticles. However, the antimicrobial performance of such a modified fabric can drastically decrease after a washing treatment. The aim of this work has been to develop antibacterial composite coatings with improved water resistance, deposited on cotton via the co-sputtering technique. The thin coatings, composed of a silica, alumina or zirconia matrix, with well embedded silver nanoclusters, were made to homogenously cover the cotton threads. The amount of silver was modulated, as was the power applied to the target, that is, 3 W for a lower amount and 5 W for a larger amount. The release of silver ions from the coatings into distilled water was very low, even after 14 days (less than 1 ppm) for all the coatings. The coated and uncoated cotton textiles were directly infected with the textile-colonizing pathogens Escherichia coli and Pseudomonas aeruginosa. After 24 h, a count of the colony forming units (CFU) revealed that the textiles coated with either the silver nanocluster/silica or zirconia matrix coatings were effective in preventing the adhesion and proliferation of E. coli bacteria, thereby preserving the textiles from contamination. However, P. aeruginosa was only absent in the case of the silica coatings or when the zirconia and alumina matrix coatings contained a large amount of silver. In all the considered cases, the CFU number was reduced with respect to the uncoated textiles. The durability of all the coatings was verified after ten washing cycles. Finally, coated textiles reported to be cytocompatible towards human fibroblasts and keratinocytes after simulating the release of toxic compounds or by directly seeding cells onto materials’ surface.