Tuning the ATP-triggered pro-oxidant activity of iron oxide-based nanozyme towards an efficient antibacterial...

An alarming increase in bacterial resistance towards various types of antibiotics makes it imperative to design alternate or combinational therapies to treat stubborn bacterial infections. In this perspective, emerging tools like nanozymes, nanomaterials with biological enzyme like characteristics, are being utilised to control infections caused by bacterial pathogens. Among several nanozymes used for antibacterial applications, Fe₃O₄ nanoparticles (NP) received great attention due to their effective peroxidase like activity. The pH dependent peroxidase activity of Fe₃O₄ NP results in generation of OH radical via the unique Fenton chemistry of iron. However, their pH dependent activity is restricted to acidic environment and dramatic loss in antibacterial activity is observed at near neutral pH. Here we describe a novel strategy to overcome the pH lacunae of citrate coated Fe₃O₄ NP by utilizing adenosine triphosphate disodium salt (ATP) as a synergistic agent to accelerate the OH radical production and restore its antibacterial activity over a wide range of pH. This synergistic combination (30 µg/mL Fe₃O₄ NP and 2.5 mM ATP) shows a high bactericidal activity against both gram positive (B. subtilis) and gram negative (E. coli) bacterial strains, in presence of H₂O₂, at neutral pH. The synergistic effect (Fe₃O₄ NP + ATP) is determined from the viability assessment and membrane damage studies and is further confirmed by comparing the concentration of generated OH radicals. Over all, this study illustrates ATP assisted and OH-mediated bactericidal activity of Fe₃O₄ nanozyme at near neutral pH.