To realize real-time and quantitative detection of reactive oxygen species (ROSs) in live-cell assays is essential to understand their roles in cellular functions, which always involve more than one types of ROSs such as hydrogen peroxide (H2O2) and superoxide (O2-). Thus, it is of great importance in monitoring different kinds of ROSs simultaneously but there still lack multiple functional biomimetic enzymes. We present here the design of a bifunctional biomimetic enzyme towards H2O2 and O2- based on an aromatic molecule imidazole (Im), which induces manganese oxide (MnOx) comprising MnO and Mn3O4 on acidified carbon nanofiber (ACNF) that is further hybridized with Au nanoparticles (Au NPs) to form a nanocomposite of Au-MnOx/Im@ACNF. MnOx on ACNF is highly active towards reduction of H2O2 and oxidation of O2-, and Au hybridization reduces high-valent-state Mn for enhanced activity towards H2O2. The nanocomposite is used to fabricate electrochemical sensing chips, which achieve a wide detection range of 0.8 μM-300 mM and 6 nM-13 μM for H2O2 and O2- with low detection limit of 70 and 0.3 nM, respectively. The chips are further demonstrated their real-time and quantitative detection of H2O2 and O2- in live-cell assay.
Keywords: Bifunctional biomimetic enzyme; Electrochemical sensing; Live-cell assay; Nanocomposite; Reactive oxygen species; Sensing chip.
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