A colorimetric/electrochemical sensor based on coral-like CuCo2O4@AuNPs composites for sensitive dopamine detection

Abstract

As a central neurotransmitter, DA (dopamine) plays a vital part in human metabolism, and its accurate detection is of great significance in disease diagnosis. In this work, we used Cu/Co bimetallic metal-organic frameworks (MOFs) as templates and gold nanoparticles (AuNPs) to construct novel nanocomposite coral-like CuCo₂O₄@AuNPs with strong peroxidase activity and electrochemical response. The coral-like CuCo₂O₄@AuNPs showed excellent peroxidase activity, and the K_m value was as low as 0.358 mM. In the presence of H₂O₂, the colorless substrate 3,3',5,5', -tetramethylbenzidine (TMB) can be catalytically oxidized into a blue product. Simultaneously, coral-like CuCo₂O₄@AuNPs, as an electroactive substance, possess strong electrocatalytic activity, which enhances the electron-transfer rate and promotes excellent current response. In the presence of DA, coral-like CuCo₂O₄@AuNPs can catalyze the oxidation of DA to dopaquinone, which further enhances the electrochemical signal. In addition, DA captures hydroxyl radicals and inhibits the oxidation of TMB, resulting in an obvious color change (blue turns colorless) and realizing colorimetric detection with the naked eye. On this basis, we successfully established a dual-mode colorimetric/electrochemical sensor using coral-like CuCo₂O₄@AuNP nanocomposites as a dual-signal probe. Combining colorimetric and electrochemical detection, the sensor achieved a wide linear range (0-1 mM) and a low detection limit (0.07 μM) for DA concentration. It was also successfully used for the detection of DA in human serum and urine with good results. In summary, this work provides an intuitive, economical, sensitive, and promising platform for DA detection.

Keywords: Colorimetric sensor; Coral-like CuCo2O4@AuNPs; Dopamine detection; Electrochemical sensor.