An electrochemical apta-assay based on hybridization chain reaction and aflatoxin B1-driven Ag-DNAzyme as amplification strategy

Herein, a novel electrochemical apta-assay based on hybridization chain reaction (HCR) and aflatoxin B1-driven Ag-DNAzyme was prepared. The combination of HCR and Ag-DNAzyme was designed for the first time as a dual signal amplification strategy for the detection of mycotoxins. The substrate DNA (sDNA) was fixed to the electrode surface, which contained the RNA A (rA) site and HCR initiation sequence. The sDNA opened the hairpin DNA structures and triggered a cascade of hybridization events. The DNA double strands formed by the HCR bound large amounts of methylene blue (MB). Aptamer and complementary DNA bound to Ag+ by C-Ag+-C complexes. AFB1 can drive Ag+ shedding, and Ag+ induced Ag-DNAzyme to shear the rA site of sDNA. The amount of binding MB decreased and the current signal decreased. Replaced biological enzymes with metal ion-mediated DNAzyme enhanced the stability of the prepared sensors while reducing the preparation cost. An adequate determination of AFB1 in corn flour, walnut powder, and other actual samples are validated, which indicated the good accuracy and potential application in real samples. The strategy is characterized by simple operation, good stability, and low preparation cost, and has good application prospects in food safety and quality control.