Color-coded Adrenaline Assay Based on GNP@MnO2 Core-shell Nanoparticles with Dark-field Microscopy

Highly sensitive visual colorimetric sensor for xanthine oxidase detection by using MnO2-nanosheet-modified gold nanoparticles

In this study, a highly sensitive colorimetric assay has been constructed for the determination of xanthine oxidase (XOD) activity by the GNP@MnO₂ core-shell nanoparticles as probe. In the presence of XOD, xanthine can be oxidized to produce H₂O₂, which makes the MnO₂ shell fallen off. With the single particle detection (SPD) based dark field microscopy (DFM), the scattering color of GNP@MnO₂ NP probe shows obvious change before and after etching process. At the single particle level, noticeable color change of the single probe can be easily detected in the existence of trace XOD. This SPD-based colorimetric strategy displays broad linear dynamic range (0.02-4 mU/mL) and low detection limit of 7.82 μU/mL, which is more sensitive than the results from ensemble sample measurement. In addition, we tested the inhibitory effect of quercetin on the activity of XOD and obtained good inhibition effect. As a consequence, this SPD-based colorimetric strategy provides new perception for the ultrasensitive detection of molecules in complex system.