Enhanced Oxidase-Mimic Constructed by Luminescent Carbon Dots Loaded on Mil-53(Fe)-No2 for Dual-Mode Detection of Gallic Acid and L-Cysteine in Food and Humans

Abstract

Monitoring of gallic acid (GA) in food and L-cysteine (Cys) in humans is crucial for body health. Nanozyme-mediated colorimetric strategy for evaluating them has been widely applied nowadays, however, the inferior efficient and susceptible single-signal recognition limit its further application. Herein, a sensitive biosensor was first constructed for bimodal detection of GA and Cys based on CDs@MIL-53(Fe)-NO2, prepared through a facile and time-saving microwave treatment. Benefiting from the excellent fluorescent and electron transfer properties of CDs, CDs@MIL-53(Fe)-NO2 exhibited significant enhanced blue fluorescence and oxidase-like activity, which could oxide colorless 3,3',5,5'-tetramethylbenzidinewithout H2O2, and the blue product could quench the fluorescence of composite. The dual-mode assay based on such bifunctional nanozyme showed an extremely sensitivity towards GA/Cys with the detection limit of 62/65 nM and 9.2/9.4 nM in colorimetric/fluorescent modes, respectively. The practicability in real samples and portability based on a smartphone of the analysis has been investigated with reliable results.

Keywords: Oxidase-mimic, Carbon dots, Metal-organic framework, Fluorescence, Colorimetry, Gallic acid