Aflatoxin B1 is one of the contamination indicators for food safety monitoring. The rapid and effective assessment and determination of AFB1 in food is of great importance to dietary safety. The lateral flow assay shows advantages in its simplicity, and rapidity, and provides a visual readout, while the available lateral flow assay for AFB1 requires a competitive format that produces readings inversely proportional to the AFB1 concentration, which is counterintuitive and may lead to a potential misinterpretation of the results. Herein, we developed a positive readout aptamer-based lateral flow strip (Apt-strip) for the detection of AFB1. This Apt-strip relies on the competition between AFB1 and fluorescein-labeled complementary DNA strands (FAM-cDNA) for affinity binding to limited aptamers against AFB1 (AFB1-Apt). In the absence of AFB1, AFB1-Apt hybridizes with FAM-cDNA. No signal at the T-line of the Apt-strip was observed. In contrast, AFB1-Apt binds to AFB1 in the sample, and then a part of the FAM-cDNA is hybridized with the free AFB1-Apt, at which time the other unreacted FAM-cDNA is captured by A35-Apt on the T-line. The signal was observed. This method achieved fast detection of AFB1 with a detection limit (DL) of 0.1 ng/mL, positive readout, and increased sensitivity.
Keywords: aflatoxin B1; aptamer; lateral flow assay; positive readout.