Enhanced oxidase-mimic constructed by luminescent carbon dots loaded on MIL-53(Fe)-NO2 for dual-mode detection of gallic acid and biothiols in food and humans

Monitoring of gallic acid (GA) in food and biothiols 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 biothiols 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 & PRIME;,5,5 & PRIME;-tetramethylbenzidine without 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/L-cysteine/homocysteine with the detection limit of 62/65/124 nM and 17/16/27 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.

Automated summary

This study successfully constructed a sensitive biosensor for the bimodal detection of gallic acid and biothiols. The biosensor was based on CDs@MIL-53(Fe)-NO2 prepared through a microwave treatment, and it utilized the excellent fluorescent and electron transfer properties of CDs for high sensitivity detection. The practicality of the method in real samples and its portability on a smartphone were demonstrated with reliable results.