Engineering defect-rich CeO₂-Pd nanozyme and investigating their ROS mediated antibacterial action.

Abstract

Uncontrolled antibiotic use increases bacterial resistance and poses threat to infectious disease management. It led to exploring nanotechnology-based antibacterial alternatives like nanozymes (Nz) which exhibit intrinsic enzyme-like catalytic action. Cerium oxide (CeO2) Nz and its composites have shown immense antibacterial potential due to their multi-enzymatic character. Nevertheless, their antibacterial potential may be enhanced through engineering CeO2 Nz that promotes bacterial adhesion along with enhanced localized-ROS generation precisely at the bacteria-nanozyme interface. Localized stress improves bactericidal efficiency at biologically safe H2O2 concentrations, addressing limitations associated with poor targeting and inefficient ROS utilization. In this context, the current study reports the engineering of defect rich CeO2-Pd Nz for enhanced ROS generation and antibacterial efficacy against Escherichia coli and Staphylococcus aureus through Pd loading. The pro-oxidative potential of the Nz was evaluated through colorimetric assays, and radical quencher/enhancer-based fluorescence assays. In vitro antibacterial efficacy of Nz was assessed using spread-plate method, live/dead staining, and biofilm studies. Loading Pd in CeO2 enhanced the oxygen vacancies and defects which consequently amplified its intrinsic peroxidase activity leading to high ROS generation. The engineered Nz demonstrated potent ROS mediated antibacterial activity against both E. coli and S. aureus. The presence of defective sites and surface roughness probably enhanced Nz-bacteria interaction and localized ROS generation which can also be observed through FE-SEM images. This close association induced oxidative stress in bacteria, leading to cell death. Furthermore, the nanozymes exhibited significant antibiofilm activity, effectively suppressing biofilm formation. The synthesized Pd loaded CeO2 Nz was highly selective in its antibacterial action and completely non-toxic toward L6 mammalian cells. The, synthesized Nz therefore, has potential to be used as a safe therapeutics for treating bacterial infections which can be explored in futuristic studies.

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