Graphene Oxide-Based Nanosensing Method for the Detection of Hydrogen Peroxide (H2O2) in Bacterial Cells

Abstract

      Reactive oxygen species (ROS) are pivotal mediators in numerous pathophysiological processes. An imbalance between ROS generation and the cellular antioxidant defense system can lead to a wide spectrum of disorders. Accurate and quantitative assessment of ROS is therefore essential for evaluating cellular oxidative status. Among ROS, hydrogen peroxide (H₂O₂) is widely regarded as a reliable biomarker of oxidative stress due to its relative stability, membrane permeability, and well-characterized role as an intracellular signaling molecule. In bacterial systems, elevated ROS levels contribute to antibiotic-induced cell death and may act as secondary mediators of cytotoxicity. Catalase, a primary antioxidant enzyme, preserves redox homeostasis by catalyzing the decomposition of H₂O₂ into water and molecular oxygen. Accordingly, the simultaneous quantification of H₂O₂ concentration and catalase activity is critical for a precise characterization of cellular redox balance. Conventional spectroscopic methods for measuring H₂O₂ and catalase are often limited by labor-intensive protocols, extensive sample preparation, and reduced sensitivity in complex biological matrices. In this study, we developed a graphene oxide–based nanosensor platform for the rapid and sensitive detection of intracellular H₂O₂. Graphene oxide, a two-dimensional carbon nanomaterial functionalized with oxygen-containing groups, possesses a high surface area and favorable electron transfer properties, making it an effective substrate for signal amplification. Its intrinsic oxidase-mimetic activity facilitates H₂O₂-dependent reactions, thereby enhancing analytical sensitivity. Moreover, the impact of silver nanoparticles on oxidative stress induction and intracellular H₂O₂ generation in Escherichia coli was investigated. Exposure to silver nanoparticles increased intracellular H₂O₂ levels, which were accurately quantified by the graphene oxide nanosensor through fluorescence emission. These results demonstrate that the proposed platform represents an efficient analytical tool for investigating oxidative stress mechanisms in microbial systems and provides a foundation for the development of redox-based diagnostic strategies in biomedical research and personalized medicine.