A novel sandwich-type electrochemical immunosensor for sensitive detection of zearalenone using NG/PDDA/HNTs and Ti-MOF-KB composites for signal amplification

In this work, a novel sandwich-type electrochemical immunosensor based on signal amplification was developed for the ultrasensitive detection of zearalenone (ZEA). The composite consisting of poly(diallyldimethylammonium chloride) functionalized nitrogen doped graphene, halloysite nanotubes and toluidine blue (Tb/NG/PDDA/HNTs), was synthesized for the first time. Then it was modified with gold nanoparticles (AuNPs) to bind the secondary antibody (Ab2, 10 μg mL-1) and form the tracer label. In addition, ketjen black (KB) was doped into titanium-based metal-organic framework (Ti-MOF), which provided large specific surface area and employed as the sensing platform to increase the immobilization of the primary antibody (Ab1, 10 μg mL-1). This immunosensor showed a wide linear range for ZEA from 10 fg mL-1 to 100 ng mL-1 with a limit of detection (LOD) as low as 0.57 fg mL-1, which was below the maximum tolerable levels (50∼100 µg kg-1) set by the United Nations Food and Agriculture Organization (FAO).