(774b) Transparent Copper-Silica Nanoparticle-Chitosan Nanocomposite Coatings with Long-Term Antibacterial Efficacy

Bacteria-contaminated inanimate surfaces within hospitals/clinics result in transmission of pathogens via direct or indirect contact, leading to increased risk of healthcare-associated infections (HAIs). Although the use of antibacterial coatings is a potential way of reducing the bacterial burden, many surfaces like instrument panels and monitors necessitate the coatings to be transparent while being highly antibacterial. In this work, a layer of acrylated quaternized chitosan (AQCS) was covalently immobilized on commercially available transparent polyvinyl fluoride (PVF) films by UV-induced grafting. Silica nanoparticles (SiO₂ NPs) were grown in situ over the AQCS-coated PVF and followed with adsorption of copper ions on the modified substrates, where the NPs acted as “storage” sites for the copper ions. The coated PVF films were transparent and SiO₂ NP-containing coatings were found to possess higher visible light transmission as compared to AQCS-coated PVF. The copper content of the coatings increased from ~2 µg/cm² to ~16 µg/cm² with increase in the SiO₂ NP deposition time from 1 h to 4 h, when the copper adsorption time was fixed at 6 h. The copper-containing coatings reduced viable bacterial count by ~99 % and 100 %, when incubated with a bacteria-loaded droplet for 60 min and 120 min respectively. The SiO₂ NP-containing coatings after being wiped 100 times with a deionized water-wetted cloth still reduced bacterial count in bacteria-loaded droplets by ~96 %, after 60 min. The stability of these coatings were further improved with the deposition of another layer of quaternized chitosan (QCS) on the SiO₂ NPs, prior to copper adsorption. These coatings with an additional QCS layer showed no significant change in antibacterial efficacy even after 100 wipes, demonstrating its stability. Additionally, these coatings showed no significant toxicity to mouse fibroblast cells. Thus, the transparent coatings developed in this work hold great potential for application as long-term antibacterial coating for combating HAIs.