An aptamer lateral flow assay for visual detection of Microcystins-LR residue in fish

Microcystin-LR (MC-LR) contamination in aquatic foods is a serious health threat to people. Here, a simple aptamer-based colorimetric lateral flow assay (LFA) was developed for on-site and visual detection of MC-LR for the first time. This detection system was designed on the basis of competition for Apt-A2C aptamer between MC-LR and its partial complementary sequence. Apt-A2C modified gold nanoparticles (AuNPs) were used as the signal reporter to realize the colorimetric readout by naked eyes, and the signal intensity of test line was inversely proportional to the concentration of MC-LR in the sample solution. Under optimized conditions, this aptamer-based LFA platform can visually detect MC-LR as low as 2.5 ng/mL with a linear range of 1-50 ng/mL, and an instrumental limit of detection of 0.84 ng/mL using a scanning strip reader. The whole assay can be finished within 5 min, starting from sample loading to color acquisition. The developed aptamer-based LFA was successfully applied in the detection of MC-LR in spiked fish tissue samples with the recovery rates ranged from 74.3% to 85.6%, and the results agreed well with those of tandem mass spectrometry. Besides, it had excellent selectivity toward MC-LR as the detection results were not affected by the potentially interfering molecules in real aquatic food matrix. Therefore, the LFA strip is an easy-to-use tool for instrument-free detection of MC-LR, and it can be applied to other toxins in aquatic foods with available aptamers.