A Portable Integrated Duplex Label-Free Electrochemical Immunosensor Constructed from a Nanozyme-Tuned Metal–Organic Framework for Dual Mycotoxin Detection

Point-of-need analysis devices are essential tools for mycotoxin detection, particularly given the frequent co-occurrence of mycotoxins in food and feed. Conventional methods capable of detecting only one mycotoxin are inadequate for comprehensive quality control of agricultural products. This study introduces, for the first time, a screen-printed duplex immunosensor for multiple detections of zearalenone (ZEN) and deoxynivalenol (DON) as a proof-of-concept using a label-free sensing platform. The immunosensor employs a UiO-66-embedded hemin nanozyme combined with amino-functionalized carbon nanotubes (UiO-66/Hemin-CNT(-NH₂)) as an electrode substrate, which not only facilitates efficient antibody immobilization but also enhances charge transfer and catalytic performance. Under optimal conditions, the immunosensor demonstrates excellent linear responses with low detection limits of 7.1 and 4.0 pg mL^-1 for ZEN and DON, respectively. The proposed duplex immunosensor also exhibits remarkable selectivity, reproducibility, and stability. The practicality of the immunosensor is validated through the analysis of real samples, including corn flour, wheat flour, and rice flour. Furthermore, the developed screen-printed dual immunosensor offers an affordable tool for on-site and real-time monitoring, leveraging a smartphone application integrated with a commercially available NFC-potentiostat. Its small size further enhances portability and usability, making it highly suitable for field applications.