Hue Recognition Competitive Fluorescent Lateral Flow Immunoassay for Aflatoxin M 1 Detection with Improved Visual and Quantitative Performance.

Immunological detection of small molecules in a point-of-care (POC) format is of great significance yet remains challenging for accurate visual discrimination and quantitative analysis. Here, we report a novel hue recognition competitive fluorescent lateral flow immunoassay (HCLFIA) strip that allows both visual and quantitative detection of aflatoxin M 1 (AFM 1 ). The HCLFIA strip works on the basis of the ratiometric change of emission, arising from the overlap of fluorescence signals of two nanocomposites tagged with probe antibodies and coated antigens. A visually discernible orange-red-to-green fluorescence color change allows the naked eye semiquantitative readout of AFM 1 around the threshold concentration (0.05 ng mL -1 ), yielding a visible detection limit of 0.02 ng mL -1 . Moreover, using a custom smartphone-based device and color chart analysis, ultrasensitive quantitative detection of AFM 1 can be achieved with a low limit of detection at 0.0012 ng mL -1 , which is considerably better than those of the previously reported colorimetric and fluorescent strips. The accuracy performed in spiked milk samples ranged from 97.91 to 113.12% with a coefficient of variation below 7.8%, showing good consistency with the results from isotope dilution liquid chromatography-tandem mass spectrometry. Thanks to the unique hue recognition scheme, the HCLFIA strip holds great potential for POC detection of small molecules.