A fluorometric assay platform for caffeic acid detection based on the G-quadruplex/hemin DNAzyme

Abstract

In this paper, a fluorometric assay platform for fluorescence detection of caffeic acid was designed based on the peroxidase-mimicking activities of G-quadruplex/hemin DNAzyme. Under the catalysis of the formed G-quadruplex/hemin complex, H₂O₂ could be decomposed into hydroxyl radicals with strong oxidation properties. Then caffeic acid would be oxidized by the released hydroxyl radicals, resulting in the product caffeic acid–quinone. Normally, caffeic acid has no influence on the fluorescence of graphene quantum dots. But when mixed with the G-quadruplex/hemin complex and H₂O₂, the fluorescence of graphene quantum dots was obviously quenched by the oxidized caffeic acid. Under the optimized experimental conditions, the quenched fluorescence intensity was linearly correlated with the concentration of caffeic acid, ranging from 2 μM to 350 μM with a detection limit of 200 nM. The proposed method was applied to the determination of caffeic acid in human serum samples with satisfactory results.