An accurate and amplifying competitive lateral flow immunoassay for the sensitive detection of haptens

We report a new competitive lateral flow immunoassay (LFIA) for hapten detection, which uses antibodies to bind antigens from a sample and form a coloured immune complex due to artificial antigens conjugated with gold nanoparticles; these were intercepted with SPA. Here, 2,4-dichlorophenoxyacetic acid (2,4-D) and gentamicin (GM) were selected as model analytes. The visual limit of detection of the 2,4-D strip was 25 ng/mL in tap water; the GM strip was 3.13 ng/mL in milk. This approach exhibits more than a 40-fold lower detection limit for 2,4-D and 3.2-fold lower for GM, which is compared to traditional LFIA using the same reagents. This approach can accurately control the amount of antibody, protect the activity of antibody and enhance the detection signal, thus improving the sensitivity of the LFIA and providing more and more sensitive methods for the development of LFIAs.