Antibacterial Activity of Copper-Loaded Plasma-Treated Natural Zeolites

摘要

Copper-exchanged zeolites (CuZ) were prepared through ion exchange at varying concentrations of copper chloride (CuCl2) solutions. The samples were tested for their antimicrobial activity against representative microorganisms of Gram-positive Staphylococ-cus aureus and Gram-negative Escherichia coli. Enhanced ion exchange capacity of natural zeolite was achieved by irradiating sodium-exchanged zeolite (NaZ) with 13.56-MHz radio-frequency argon (Ar) discharged for 20 min at 25 W power. We compared the Cu uptake of pristine and plasma-treated samples soaked in 10,20, 30, 40, and 50 dim CuCL2, solutions using energy dispersive-X-ray fluorescence spectroscopy. An increase in Cu uptake was realized when NaZ was treated with Ar plasma. The physical effect of plasma treatment was observed under a scanning electron microscope. We found, in particular, that the Ar gas discharge was able to etch through the surface of the zeolite samples, creating more active sites for ion exchange. Mueller-Hinton antimicrobial assays further verified the successful incorporation of Cu into the zeolite framework by the appearance of inhibition zones in the E. coli and S. aureus cultures, an indication of antimicrobial activity due to the presence of Cu and its oxides.