Peroxidase-Mimetic Activity of Pollutant-Soot-Derived Cytocompatible Onion-like Nanocarbon for Colorimetric Detection of H2O2 and Sequential Sensing of Epinephrine

Abstract Herein, we report a peroxidase-mimic activity of pollutant-soot-derived onion-like nanocarbon (ONC). The functionalized version of ONC (Oxi-ONC) showed good peroxidase activity and was used for the colorimetric detection of hydrogen peroxide (H2O2) using 3,3′,5,5′-tetramethylbenzidine (TMB) as a chromogenic substrate. Oxi-ONCs exhibit peroxidase-like activity that oxidizes TMB to its blue-colored product via the generation of reactive oxygen species (ROS). Batch experiments under optimized conditions exhibit colorimetric detection of H2O2 with an LOD of 0.25 μM and a linear range of 2.5–50 μM. Furthermore, the oxidized TMB separated from the Oxi-ONC–TMB conjugate has been used to detect epinephrine (adrenaline), in which, upon addition of epinephrine, the blue complex fades to colorless, with an LOD of 0.18 μM and a linear range of 2.5–30 μM. The viability of the proposed sensor for detecting H2O2 in a real milk sample and for EP in a human saliva sample has also been demonstrated. In continuation, Oxi-ONC showed cytocompatibility, as assessed by hemocompatibility, MTT, and LDH assays (evaluating the viability of NIH 3T3 fibroblast cells), with no specific toxicity observed at the higher concentration.