Transparent Copper-Based Antibacterial Coatings with Enhanced Efficacy against Pseudomonas aeruginosa

Bacterial surface contamination is a major cause of hospital-associated infections. Antibacterial coatings can play an important role in reducing bacterial transmission via inanimate surfaces in healthcare settings. In this work, transparent copper-based antibacterial coatings were fabricated on commercial poly(vinyl fluoride) and stainless steel. Acrylated quaternized chitosan and ethylenediaminetetraacetic acid were covalently grafted on the substrate for complexation with copper ions. The number of viable Staphylococcus aureus in a droplet [containing ∼10⁴ colony forming units (CFU)], deposited on the copper-containing coating decreased by ∼96% within 60 min at 25 °C. With Pseudomonas aeruginosa, one of the most virulent and hardest to kill bacteria, no CFU could be observed within the same time span (killing efficacy >99.8% based on the detection limit). An increase in copper release from the coating was observed in the presence of P. aeruginosa, which was postulated to be due to the proteolytic activity of P. aeruginosa. The higher efficacy of the coating against P. aeruginosa compared to S. aureus is thus attributed to this increased copper release from the coating, which resulted in extensive bacterial membrane damage and death. The copper-containing coating on poly(vinyl fluoride) retained its antibacterial efficacy after 100 wipes with a water-wetted cloth or isopropanol wipes, demonstrating its durability and long-term efficacy. The coating did not exhibit significant cytotoxicity toward mammalian fibroblasts, further demonstrating its potential for mitigating bacterial transmission in a clinical setting.