Signal-on lateral flow immunoassays for rapid detection of tetrodotoxin in pufferfish

Small-molecule biotoxins are frequently founded in grains, corns, peanuts, and different kinds of aquatic products, and they are harmful to human health. Lateral flow immunoassays (LFIAs) have been widely used for on-site detection of small-molecule biotoxins. However, most of the reported LFIAs approaches are signal-off type because each small-molecule biotoxin only has one antigen binding site due to the small size of the molecule. In this work, we demonstrate a signal-on LFIAs approach for on-site detection of small-molecule biotoxin based on the aptamer/antibody molecular recognition system, and the detection of tetrodotoxin (TTX) was selected as an example. A TTX specific aptamer with high affinity was modified on the gold nanoparticles (AuNPs) to act as the colloid gold labels, and a TTX specific antibody was immobilized on the testing line of the LFIAs to act as the capture antibody. This aptamer/antibody combinations not only allow qualitative screening by the naked eye but also enable semi-quantitative detection when combined with smartphone measurement of RGB values. The detection range was 8-100 ng/mL, with a detection limit of 8 ng/mL, and recoveries ranging from 99.00% to 110.95%. The RSD for intra-batch reproducibility was 6.98%, and the RSD for batch-to-batch reproducibility was 5.20%. Meanwhile, the proposed LFIAs was successfully demonstrated for the detection of TTX in globefish indicating that the aptamer sensor has good homogeneity for the detection of TTX.