Fluorescence based immunochromatographic sensor for rapid and sensitive detection of tadalafil and comparison with a gold lateral flow immunoassay.

Tadalafil (TDL) is an illegal additive drug found in drinks and functional foods that could threaten public health. There was a great concern whether the adulteration occurred in coffee added with similar type of herbs. Here we have developed a rapid, simple, sensitive, and semi-quantitative lateral flow immunoassay (LFIA) based on gold and fluorescence labelled monoclonal antibody (mAb) for detection of TDL in coffee sample. Under optimal conditions, the cut off limits using gold nanoparticles labelled mAb (GLM) was found to be 250 ng/mL and 100 ng mL using fluorescent labelled mAb (FLM) in coffee samples. The coffee samples were spiked with TDL, and the LFIA with GLM gave average recoveries of 92-105.3% (intra-assay) and 96.6-105.9% (inter-assay), meanwhile with FLM gave recoveries 97.9-107.3% (intra-assay) and 98.3-108.9% (inter-assay). Results gave LFIA with FLM more sensitive than with GLM and all the test can be completed within 10 min, which would be an option for convenient and rapid assay of TDL detection.