Ratiometric Fluorescent Lateral Flow Immunoassay for Point‐of‐Care Testing of Acute Myocardial Infarction

We report the development of a highly sensitive ratiometric fluorescent lateral flow immunoassay (RFLFIA) strip for rapid and accurate detection of acute myocardial infarction biomarker, namely heart‐type fatty acid binding protein (H‐FABP). The RFLFIA strip works in terms of ratiometric change of fluorescence signal, arising from blending of fluorescence emitted by two composite nanostructures conjugated to capture and probe antibodies and inner filter effect of gold nanoparticles. In conjunction with using custom smartphone‐based analytical device and tonality analysis, quantitative detection of H‐FABP was achieved with a low limit of detection at 0.21 ng mL−1. The RFLFIA strip can generate a visually distinguishable green‐to‐red color change around the threshold concentration of H‐FABP (6.2 ng mL−1), thus allowing the semi‐quantitative diagnosis by the naked eye. Ratiometric fluorescent lateral flow immunoassay is achieved by inner filter effect‐mediated double‐signal‐reverse change, which not only enables highly sensitive quantitative analysis by combing with the smartphone platform, but also allows the visual readout of H‐FABP concentration by the naked eye. The developed strip can be used for rapid and accurate point‐of‐care testing of acute myocardial infarction.