Target-responsive aptamer-cross-linked hydrogel sensors for the visual quantitative detection of aflatoxin B

For the on-site detection of aflatoxin B1 (AFB1), a DNA hydrogel was prepared as a biosensor substrate, while an AFB1 aptamer was used as the recognition element. An AFB1-responsive aptamer-cross-linked hydrogel sensor was constructed using an enzyme-linked signal amplification strategy; AFB1 binds competitively to the aptamer, causing the hydrogel to undergo cleavage and release horseradish peroxidase (HRP). The addition of exonuclease I (ExoI) to the hydrogel causes the release of AFB1 from the aptamer, promoting additional hydrogel cleavage to release more HRP, ultimately catalysing the reaction between 3,3',5,5'-tetramethylbenzidine and H2O2. The hydrogel sensor exhibited an outstanding sensitivity (limit of detection, 4.93 nM; dynamic range, 0-500 nM), and its selectivity towards seven other mycotoxins was confirmed. The feasibility and reliability were verified by measuring the AFB1 levels in peanut oil (recoveries, 89.59-95.66 %; relative standard deviation, <7%); the obtained results were comparable to those obtained by UPLC-HRMS.