Polyelectrolyte multilayer films containing silver as antibacterial coatings

A facile approach to fabrication of transparent antimicrobial coatings based on polyelectrolyte multilayers (PEMs) is presented. Counterions existing in PEMs were utilized via ion exchange and in situ reduction to incorporate into the films silver ions and nanoparticles, and the antibacterial efficacy of the films against E. coli was assessed by the Kirby-Bauer method. The PEMs containing silver in the ionic form exhibited high activities in short terms, and the antibacterial effects depended on the ionic strength in the polyelectrolyte solutions used for the PEM fabrication. The PEMs loaded with silver nanoparticles showed lower initial bactericidal effects, but remained active after long periods of time, and the antimicrobial performance can be improved by increasing the silver loading through repeating the ion-exchange/reduction cycle for multiple times. The films were transparent in the visible region. Coatings containing multiple antimicrobial agents for possible synergistic effects can be fabricated in a single process using this method.