Defect-rich nickel-doped ceria nanozymes for ROS-mediated antibacterial therapy

Aim To synthesize defect-rich nickel-doped ceria (Ni-CeO2) nanocomposites with enhanced reactive oxygen species (ROS)-mediated antibacterial activityMaterials and methods Ni-CeO2 nanocomposite was synthesized through reduction of Ni2+ ions on ceria nanopowder using sodium borohydride (NaBH4). Structural and surface characterizations were performed using X-ray diffraction (XRD), Raman spectroscopy, transmission electron microscopy (TEM), energy-dispersive X-ray analysis (EDX), and X-ray photoelectron spectroscopy (XPS). Pro-oxidative (peroxidase and oxidase) mimic activity, ROS generation assay, antibacterial activity of nanocomposite against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus), and in vitro cytotoxicity on LNCaP and A431 cell lines were evaluated.Results Nickel doping increased the lattice strains (defects), enhanced oxygen-vacancy formation, and promoted Ce3+/Ce4+ redox cycling, resulting in significantly improved pro-oxidative mimic activity compared with CeO2. The Michaelis–Menten constant (Km) decreased from 0.3 to 0.1 mM, while Vmax increased 2.5-fold. The Ni-CeO2 nanozymes achieved 82.11% reduction of E. coli and 78.58% reduction of S. aureus at only 100 µM H2O2. Cytotoxicity studies confirmed biocompatibility at antibacterial concentrations.Conclusions Defect-rich Ni-CeO2 nanocomposite showed enhanced ROS-mediated antibacterial activity and represent promising antimicrobial nanozyme plateform for treating bacterial infections.