Engineering Rechargeable Antibacterial Coatings on Stainless Steel for Efficient Inactivation of Pathogenic Bacteria in the Presence of Organic Matter

Worldwide, around 600 million people are affected by foodborne illnesses each year which highlights the importance of food safety. It is important to ensure the cleanliness of the working surfaces in food processing facilities. Stainless steel is widely used in the food industry as a food contact surface. Endowing stainless steel with a potent rechargeable antibacterial function offers the prospect of a reusable and clean surface. In this study, a clickable coating for stainless steel was developed. Quaternized azido-hydantoin (C1), quaternary ammonium compound (C2), and azido-hydantoin (C3) were bonded to stainless steel primed with the clickable coating to yield three samples: SSMC1, SSMC2, and SSMC3, respectively. The coating was stable during the chlorination process which was used to convert the immobilized C1 and C3 to their N-chloramine counterparts (SSMC1-Cl and SSMC3-Cl, respectively). It was shown that SSMC1-Cl had the best antibacterial activity with 100% reduction of E. coli and S. aureus after 1 and 2 h of contact, respectively. SSMC1-Cl also showed the best performance in high protein medium (HPM) against bacteria, demonstrating 100% and 99.9% bacterial reduction against E. coli and S. aureus, respectively, after 3 h of contact. After five cycles of chlorination-dechlorination, SSMC1-Cl sustained a kill efficiency of 100% for both E. coli and S. aureus within 2 h of contact. This result reveals that SSMC1-Cl has the ability to maintain its antibacterial activity after repetitive cycles, which emphasizes its rechargeable nature. Altogether, this study presents an effective quaternized N-chloramine-based biocidal coating on stainless steel (SSMC1-Cl) that is rechargeable, durable, and effective against Gram-positive and Gram-negative bacteria.