Dual-Terminal Stemmed Aptamer Beacon for Label-Free Detection of Aflatoxin B1 in Broad Bean Paste and Peanut Oil via Aggregation-Induced Emission.

Aflatoxin B1 (AFB1) contamination ranks as one of the most critical food safety issues, and assays for its on-site monitoring are highly demanded. Herein, we propose a label-free, one-tube, homogeneous, and cheap AFB1 assay based on a finely tunable dual-terminal stemmed aptamer beacon (DS aptamer beacon) and aggregation-induced emission (AIE) effects. The DS aptamer beacon structure could provide terminal protection of the aptamer probe against exonuclease I and confer specific and quick response to target AFB1. In comparison to the conventional molecule beacon structure, the stability of the DS aptamer beacon could be finely tuned by adjusting its two terminal stems, allowing for elaborately optimizing probe affinity and selectivity. By the utilization of an AIE-active fluorophore, which would be lighted up by aggregating to negatively charged DNA, AFB1 could be determined in a label-free manner. The proposed method could quantify AFB1 in one test tube using two unlabeled DNA strands. It has been successfully applied for analyzing AFB1 in peanut oil and broad bean sauce, with total recoveries ranging from 92.75 to 118.70%. Thus, the DS aptamer beacon-based assay could potentially facilitate real-time monitoring and controlling of AFB1 pollution.