Development of an electrochemical surface enhanced raman spectroscopy (EC-SERS) fabric sensor to detect cortisol for early diagnosis of post-traumatic stress disorder

Abstract

Early diagnosis of Post-Traumatic Stress Disorder (PTSD) is challenging. Its prevalence rate in Canada is 9.2%. Experiencing stress for a sustained period can lead to a prolonged release of cortisol that causes negative feedback which leads to an eventual decrease in cortisol levels in PTSD patients. Electrochemical Surface Enhanced Raman Spectroscopy (EC-SERS) deals with enhancement of metal nanoparticles under application of voltage to detect the analyte signal. ECSERS is advantageous for detecting biological samples. Here we report using blend fabric (37% silk, 35% hemp, 28% organic cotton) for the development of a functional fabric sensor using ECSERS to detect cortisol for early diagnosis of PTSD. Cortisol is a glucocorticoid stress hormone and a challenging molecule to be detected with EC-SERS. The fabric sensor is comprised of a counter electrode, reference electrode, and working electrode. The counter electrode and working electrode are printed on fabric with carbon ink on top of silver ink and the reference electrode is imprinted on fabric with silver conductive ink. To provide effective SERS enhancement, silver nanoparticles were deposited on the working electrode area. For proof-of-concept studies, a 1 mg/mL analytical standard of cortisol in methanol was used for these investigations. Cortisol signal increased with an increase in the application of negative voltage. Quantitative analysis of signal intensity with cortisol concentration was also evaluated. To determine the relationship between peak intensity and analyte concentration, EC-SERS studies were conducted with 50 µL, 65 µL, 75 µL, and 100 µL of 1 mg mL^_-1 cortisol. In summary, a fabric-based EC-SERS sensor for the detection of cortisol was demonstrated, paving the way to a wearable sensor for early PTSD diagnostics.