A Cost-Effective Paper-Based SERS Device for the Detection of Cortisol in Saliva

Cortisol levels in saliva is an important biomarker of stress and its rapid detection is a significant need for overall management of health and wellness. Herein, we demonstrate two novel SERS-based approaches for the detection of cortisol directly in saliva using regular and novel hexagonal gold nanoparticles (AuNPs) on a paper substrate. Using the direct SERS method, we first show the detection of cortisol by mixing the cortisol solution with highly concentrated AuNPs on a Parchment paper surface as an active SERS substrate. We also propose an alternate lateral flow SERS (LFS) approach, which employs paper as a chromatographic channel to reduce interference from background saliva matrix for the detection using SERS. A rapid detection of spiked cortisol in saliva down to 100 µg/ml concentration by employing the 'lateral flow SERS' (LFS) platform is shown. Results indicate a promising route for point-of-care detection of stress biomarkers.