A neoteric antibacterial ceria-silver nanozyme for abiotic surfaces

Abstract

Community-associated and hospital-acquired infections caused by bacteria continue to yield major global challenges to human health. Bacterial contamination on abiotic surfaces is largely spread via high-touch surfaces and contemporary standard disinfection practices show limited efficacy, resulting in unsatisfactory therapeutic outcomes. New strategies that offer non-specific and broad protection are urgently needed. Herein, we report our novel ceria-silver nanozyme engineered at a molar ratio of 5:1 and with a higher trivalent (Ce³⁺) surface fraction. Our results reveal potent levels of surface catalytic activity on both wet and dry surfaces, with rapid, and complete eradication of Pseudomonas aeruginosa, Staphylococcus aureus, and methicillin resistant S. aureus, in both planktonic and biofilm form. Preferential electrostatic adherence of anionic bacteria to the cationic nanozyme surface leads to a catastrophic loss in both aerobic and anaerobic respiration, DNA damage, osmodysregulation, and finally, programmed bacterial lysis. Our data reveal several unique mechanistic avenues of synergistic ceria-Ag efficacy. Ag potentially increases the presence of Ce³⁺ sites at the ceria-Ag interface, thereby facilitating the formation of harmful H₂O₂, followed by likely permeation across the cell wall. Further, a weakened Ag-induced Ce-O bond may drive electron transfer from the E_c band to O₂, thereby further facilitating the selective reduction of O₂ toward H₂O₂ formation. Ag destabilizes the surface adsorption of molecular H₂O₂, potentially leading to higher concentrations of free H₂O₂ adjacent to bacteria. To this end, our results show that H₂O₂ and/or NO/NO₂^-/NO₃^- are the key liberators of antibacterial activity, with a limited immediate role being offered by nanozyme-induced ROS including O₂^•- and OH^•, and likely other light-activated radicals. A mini-pilot proof-of-concept study performed in a pediatric dental clinic setting confirms residual, and continual nanozyme antibacterial efficacy over a 28-day period. These findings open a new approach to alleviate infections caused by bacteria for use on high-touch hard surfaces.

Keywords: Agent; Antibacterial; Biocidal; Biofilm; Ceria; Disinfection; Infection; Silver.