Development of a Lateral Flow Strip with a Positive Readout for the On-Site Detection of Aflatoxin B 1 .

Aflatoxin B 1 is one of the contamination indicators for food safety monitoring. The rapid and effective assessment and determination of AFB 1 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 1 requires a competitive format that produces readings inversely proportional to the AFB 1 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 1 . This Apt-strip relies on the competition between AFB 1 and fluorescein-labeled complementary DNA strands (FAM-cDNA) for affinity binding to limited aptamers against AFB 1 (AFB 1 -Apt). In the absence of AFB 1 , AFB 1 -Apt hybridizes with FAM-cDNA. No signal at the T-line of the Apt-strip was observed. In contrast, AFB 1 -Apt binds to AFB 1 in the sample, and then a part of the FAM-cDNA is hybridized with the free AFB 1 -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 1 with a detection limit (DL) of 0.1 ng/mL, positive readout, and increased sensitivity.