(680d) Electroless Deposition of Copper on Quaternized Chitosan Coatings for Antibacterial Application

Surface modification techniques are useful for the development of various functional materials, while preserving the bulk properties. In this work, we seek to develop antimicrobial surface coatings that can help to reduce the transmission of pathogens within a clinical environment. Our focus is on chitosan derivatives since chitosan is an inexpensive, nontoxic naturally derived polysaccharide which is known to possess broad antimicrobial activity. The quaternization of chitosan greatly increases its solubility in water as well as its antimicrobial efficacy. Quaternized chitosan (QCS) modified with acrylate groups were grafted on polymer films under UV irradiation to give highly stable, non-cytotoxic QCS coatings. When bacteria-contaminated droplets were placed in contact with these coatings, about 90% of the bacterial cells were killed after 2 h. We hypothesized that the antibacterial efficacy could be further increased by the introduction of copper on the QCS-grafted films. Electroless deposition of copper on the QCS coatings was carried out, with and without catalytic pre-treatment using acidic PdCl₂. The total copper content of the coatings with and without PdCl₂ pretreatment was similar at ~ 4 µg/cm², after 1 h of electroless deposition. Thus, the positively charged quaternary ammonium groups of QCS promoted deposition of copper on the surface without the necessity of catalytic pre-treatment. XPS analyses showed that majority of the copper on the surface was Cu(0) species. Copper-containing QCS coatings reduced bacterial count by 95% and 100%, when placed in contact with contaminated droplets for 1 h and 1.5 h respectively. Additionally, the copper-containing films were found to have no significant cytotoxic effects on fibroblast cells placed in contact with these films. Thus, these copper-containing films with high antibacterial efficacy can potentially be placed over high-touch areas in hospitals to prevent pathogen transmission.