A robust dual-readout ratiometric assay for dopamine based on NiMn2O4-catalyzed DHNP fluorophore conversion

Abstract

Dopamine (DA), a critical biomarker closely associated with the onset and progression of neurological disorders, was sensitively quantified using dual enzyme-mimetic NiMn₂O₄ nanoflowers. The nanozyme simultaneously exhibits peroxidase- and oxidase-like activities, catalyzing a highly selective cyclization reaction between DA and 1, 3-dihydroxynaphthalene (DHNP). As the DA concentration increased, the intrinsic fluorescence of DHNP at 440 nm was progressively quenched, accompanied by the formation of a new optically active fluorophore with emission at 485 nm and a corresponding absorbance at 455 nm. This dual-mode ratiometric fluorescence–colorimetric sensing strategy enabled self-calibrated detection, effectively minimizing signal fluctuation and matrix interference. The platform displayed excellent linearity over the range of 0–250 µM for fluorescence and absorbance responses, allowing accurate, sensitive, and selective DA determination. Owing to its robustness and reliability, the proposed method is well suited for high-throughput dopamine analysis in diverse biological sample matrices.