Salivary Electrochemical Cortisol Biosensor Based on Tin Disulfide Nanoflakes

Wai-Ching Liu,Sanford P C Hsu,Ching-Shu Lo,Yunqian Li,Yuehua Hong,Xinrui Liu,Xinke Liu,Sasza Chyntara Nabilla,Yu-Chien Lin,Chingpo Lin,Gang Zhao,Yi-Min Wang,Ren-Jei Chung,Zhiwen Li

doi:10.1186/s11671-019-3012-0

Abstract

Cortisol, a steroid hormone, is secreted by the hypothalamic-pituitary-adrenal system. It is a well-known biomarker of psychological stress and is hence known as the “stress hormone.” If cortisol overexpression is prolonged and repeated, dysfunction in the regulation of cortisol eventually occurs. Therefore, a rapid point-of-care assay to detect cortisol is needed. Salivary cortisol electrochemical analysis is a non-invasive method that is potentially useful in enabling rapid measurement of cortisol levels. In this study, multilayer films containing two-dimensional tin disulfide nanoflakes, cortisol antibody (C-Mab), and bovine serum albumin (BSA) were prepared on glassy carbon electrodes (GCE) as BSA/C-Mab/SnS2/GCE, and characterized using electrochemical impedance spectroscopy and cyclic voltammetry. Electrochemical responses of the biosensor as a function of cortisol concentrations were determined using cyclic voltammetry and differential pulse voltammetry. This cortisol biosensor exhibited a detection range from 100 pM to 100 μM, a detection limit of 100 pM, and a sensitivity of 0.0103 mA/Mcm2 (R2 = 0.9979). Finally, cortisol concentrations in authentic saliva samples obtained using the developed electrochemical system correlated well with results obtained using enzyme-linked immunosorbent assays. This biosensor was successfully prepared and used for the electrochemical detection of salivary cortisol over physiological ranges, based on the specificity of antibody-antigen interactions.

Highlights

Cortisol, a steroid hormone, is secreted by the hypothalamic-pituitary-adrenal (HPA) system
Cortisol levels follow a circadian rhythm over a 24-h cycle; the highest levels are observed early morning, and the levels progressively reduce by night [3–6]
The results demonstrate that this bovine serum albumin (BSA)/Cortisol antibody (C-Mab)/SnS2/glassy carbon electrodes (GCE) can be employed for electrochemical cortisol sensing in biologically relevant fluids such as saliva

Summary

Introduction

A steroid hormone, is secreted by the hypothalamic-pituitary-adrenal (HPA) system. It is a well-known biomarker of psychological stress and called the “stress hormone” [1, 2]. Cortisol levels follow a circadian rhythm over a 24-h cycle; the highest levels are observed early morning, and the levels progressively reduce by night [3–6]. Excessive levels of cortisol can cause Cushing’s disease, with symptoms of central obesity, purple striae, and proximal muscle weakness. Reduced levels of cortisol can lead to Addison’s disease, with chronic fatigue, malaise, anorexia, postural hypotension, and hypoglycemia [7–9]. Maintaining appropriate cortisol balance is essential for human health

Methods

Results

Conclusion