A Novel Branch-Type Electrochemical-Colorimetric Sensor Based on Bifunctional Aupt/Nife-Pba Nanoenzymes Synergized with Peony-Like Au/Znni Nfs

Abstract

Herein, a novel branch-type electrochemical-colorimetric dual-mode sensor, which utilizes the synergistic effect of bifunctional AuPt/NiFe-PBA and Au/ZnNi NFs, was developed to detect Ochratoxin A (OTA). It was verified that the prepared AuPt/NiFe-PBA not only provides excellent redox signals in electrochemical mode, but also exerts strong catalytic activity in colorimetric mode, which makes it an ideal bifunctional signal probe. To further improve the signal response, we designed and constructed a branch-type DNA structure. This structure effectively increases the participation of the bifunctional probe AuPt/NiFe-PBA and achieves signal amplification. Magnetic separation technology was effectively utilized to separate the electrochemical and colorimetric channels, enabling dual-mode detection. In addition, peony-like Au/ZnNi NFs were used as electrode modification materials, which provided a large number of active sites and high conductivity, resulting in a significant electrochemical signal enhancement of 41%. This dual-mode sensor improves the reliability of detection by mutual validation of the two detection modes. In electrochemical mode, the linear range of the sensor for the detection of OTA was 0.001-500 ng/mL with a detection limit of 0.40 pg/mL. In colorimetric mode, the linear range of the sensor was 0.001-500 ng/mL with a detection limit of 0.29 pg/mL. The sensor has good selectivity, repeatability and reproducibility, and has been successfully applied to the determination of OTA in corn flour, wine and quality control samples of coarse rice powder and wheat flour.

Keywords: Electrochemical-colorimetric dual-mode sensor, AuPt/NiFe-PBA, Branch-type DNA structure, Peony-like Au/ZnNi NFs