Development of colorimetric paper-based analytical device for cortisol detection

Abstract

Nowadays, the detection of cortisol can play a key role in understanding stress-related diseases. Several competitive immunoassay formats have been reported for the detection of this small hormone molecule. Lateral flow immunoassay (LFIA) is one of the most widely used platforms that offer its simplicity and rapidity for such analysis. Unlike previous sensors for cortisol sensing that require complicated readers, specialized reagents, or even post-treatment methods to amplify the obtained signal, in this work, we employed a concave test zone constructed on the LFIA device (cLFIA) which can directly enhance the signal response as the flowing sample was substantially concentrated before passing through the immobilized antibody. Nearly 2-fold sensitivity enhancement was obtained using this straightforward immunoassay format. A smartphone was used as a detector and the linear calibration plot of this cLFIA was established in the range of 5 to 5,000 ng mL-1 with an LOD and LOQ of 1.6 and 4.8 ng mL-1, respectively. From the result, it could be concluded that this cLFIA device could be applied to detect cortisol in human serum effectively. In addition, This cLFIA device is believed to explore new possibilities for the determination of other protein compounds and exploit them in point-of-care testing.