Purpose: In this work we describe the design of polymeric antimicrobial coatings which incorporate N-halamine antimicrobial moieties which regenerate antimicrobial activity with exposure to halogenated sanitizers.
Methods: Using layer-by-layer deposition and coat-cure technologies, alternating polyamine and polyacrylic acid (or polyanhydride) polymers were deposited onto stainless steel, polyethylene, and polypropylene materials. Both dip and spray-on application techniques were explored. Material chemistry was characterized by Fourier transform infrared spectroscopy, colorimetric halamine quantification assays, and water contact angle. Antimicrobial activities were characterized by submerging coupons of coated substrates in an aqueous suspension of Listeria monocytogenes for varying contact periods. Experiments were performed in quadruplicate (n = 4) on at least two independent days to verify repeatability of results. Significance was determined using the general linear model followed by Tukey's pairwise comparisons using a confidence interval of 95%.
Results: We have introduced sufficient N-halamine functionality in these polymeric antimicrobial coatings to inactivate greater than 5-log cycles of Listeria monocytogenes. Materials were able to regenerate antimicrobial activity after 100 rechlorination cycles, and prolonged exposure to both acidic and alkali clean-in-place chemical agents. Tailoring the chemistry of the polymers used in the nanoscale coating process resulted in retained antimicrobial character even after chlorine dissociation from the surface.
Significance: Such rechargeable antimicrobial polymer coatings can aid in improving food safety by reducing cross-contamination of microorganisms from food processing equipment.