Lateral Flow Immunoassay with a Concave Test Spot for the Determination of Cortisol in Human Serum

Abstract

Monitoring cortisol levels is a key step in the investigation of stress-related diseases. Among the approaches that have been reported for this hormone, the lateral flow immunoassay (LFIA) is widely used due to its simplicity, portability, and rapidity. However, LFIA sensors for cortisol sensing generally require complicated readers, specialized reagents, or even post treatment methods to amplify the obtained signal. Herein, we report an LFIA device having a concave test zone (cLFIA) that directly enhanced the response as the flowing sample is substantially concentrated before passing through the immobilized antibodies, achieving a nearly two-fold sensitivity enhancement. Using smartphone-based detection, a linear calibration plot of this cLFIA was established from 5 to 5000 ng/mL with limits of detection (LOD) and quantification of 1.6 and 4.84 ng/mL, respectively. The sensor was also employed for human serum analysis, affording results that were in good agreement with a standard electrochemiluminescence protocol according to a statistical paired t-test. This cLFIA device provides a new platform for the determination of proteins with potential application in point-of-care testing.

Keywords:

• Lateral flow immunoassay
• concave test spot
• cortisol
• spectrophotometry
• colorimetric detection
• competitive immunoassay

Acknowledgments

This work was supported by the National Research Council of Thailand (NRCT): N41A640073 and Ratchadapiseksompoch Endowment Fund, Chulalongkorn University. In addition, NK and SC are also thankful for financial support from Chulalongkorn University (CU_GR_62_80_61_03).

Conflict of interest

There are no conflicts of interest to declare.