Development of a Lateral Flow Strip with a Positive Readout for the On-Site Detection of Aflatoxin B

Aflatoxin B is one of the contamination indicators for food safety monitoring. The rapid and effective assessment and determination of AFB 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 AFB requires a competitive format that produces readings inversely proportional to the AFB 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 AFB. This Apt-strip relies on the competition between AFB and fluorescein-labeled complementary DNA strands (FAM-cDNA) for affinity binding to limited aptamers against AFB (AFB-Apt). In the absence of AFB, AFB-Apt hybridizes with FAM-cDNA. No signal at the T-line of the Apt-strip was observed. In contrast, AFB-Apt binds to AFB in the sample, and then a part of the FAM-cDNA is hybridized with the free AFB-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 AFB with a detection limit (DL) of 0.1 ng/mL, positive readout, and increased sensitivity.