Sensitive electrochemical detection of aflatoxin B1 using DNA tetrahedron-nanostructure as substrate of antibody ordered assembly and template of aniline polymerization.

A novel strategy for AFB1 detection in grains was proposed based on DNA tetrahedron-structured probe (DTP) and horseradish peroxidase (HRP) triggered polyaniline (PANI) deposition. Briefly, the DNA tetrahedron nanostructures were assembled on the gold electrode, with carboxylic group designed on top vertex of them. The carboxylic group was conjugated with the AFB1 monoclonal antibody (mAb) to form DTP. The test sample and a known fixed concentration of HRP-labeled AFB1 were mixed and they compete for binding to DTP. The HRP assembled on the gold electrode catalyzed the polymerization of aniline on DTP. AFB1 in grains could be determined by using PANI as electrochemical signal molecules. Interestingly, DNA tetrahedron-structure, which has mechanical rigidity and structural stability, can improve antigen-antibody specific recognition and binding efficiency through the use of mAb ordered assembly. Meanwhile, nucleic acid backbone with a large amount of negative charge is good template for aniline polymerization under mild conditions.