A novel immunocolorimetric probe for aflatoxin B1 based on multifunctional metal−organic frameworks

In this work, the Cu-based metal−organic frameworks composite, labelled as GOx@HKUST-1 @antibody, was prepared by simple reaction at room temperature to construct a competitive immunocolorimetric Aflatoxin B1(AFB1) sensor. In this assay, the HKUST-1 composite was given a triple function: glucose oxidase(GOx) stabilizer, peroxidase mimic and carrier material of AFB1 antibody. Under coordination modulation of benzoic acid, glucose oxidase encapsulated HKUST-1 presented octahedron with uniform size (average size: 10.3 µm), which was conducive to the immune reaction and magnetic separation. By immune combination and magnetic separation, GOx@HKUST-1 @antibody was redispersed and used as reactor of the cascade to amplify the detection signal. With the help of the external HKUST-1, GOx can catalyze glucose to produce hydrogen peroxide to oxidize 3,3′,5,5′-tetramethylbenzidine (TMB), which turns the solution blue. The target AFB1 can compete with AFB1-BSA-modified Fe3O4 nanoparticles for GOx@HKUST-1 @antibody, which can result to the decreasing of the color signal. The method showed ultra high sensitivity for AFB1 with a detection limit of 0.004 ng mL−1, and high stability owing to the protection effect of HKUST-1 on the GOx and antibody. In addition, such competitive immunoassays can be extended to the detection of other biotoxin targets.