Toxicity and Antimicrobial Properties of ZnO@ZIF-8 Embedded Silicone against Planktonic and Biofilm Catheter-Associated Pathogens

A ZnO@ZIF-8 powder on a gram scale was prepared via treatment of ZIF-8 with silver nitrate to induce spontaneous formation of ZnO nanorods on the surface of the ZIF-8 crystals. The crystal structure, phase purity, and physicochemical characteristics of ZnO@ZIF-8 were determined by X-ray diffraction, high-resolution electron microscopy, energy-dispersive spectroscopy, and nitrogen adsorption. The antimicrobial potential of ZnO@ZIF-8 for reduction of microorganisms often implicated with catheter-associated urinary tract infections (CAUTIs) was studied in detail using four target pathogens, Escherichia coli, Klebsiella pneumoniae, Proteus mirabilis, and Staphylococcus aureus. The ability of the compound to kill all four microorganisms in suspension was established, and a minimum bactericidal concentration of 0.25 mg mL–1 was determined for each microorganism. ZnO@ZIF-8 compound was found to be no more toxic to Galleria mellonella than distilled water, which was assessed by injection of Galleria with 10 μL of ZnO@ZIF-8 of concentrations of up to 2 mg mL–1. ZnO@ZIF-8 suspensions (2 mg mL–1 concentration) were able to reduce well-established biofilms of all four organisms containing between 107 and 109 CFU mL–1 to below limit of detection (BLD) over a 24 h period. Silicone-embedded ZnO@ZIF-8 (2 or 4 wt % ZnO@ZIF-8 loading) also demonstrated antimicrobial properties with all four microorganisms being eliminated from the surface within 24 h. The ZnO@ZIF-8 high potency and rapid antibiofilm activity against all four test organisms coupled with its nontoxicity offer a new avenue for control of microbial colonization of catheters, which would ultimately result in reduction of CAUTIs.