SnO2 nanoflakes deposited carbon yarn-based electrochemical immunosensor towards cortisol measurement

Textile and garment-based biosensing approaches allow the integration of diagnostic devices in wearable format, which can be used to develop non-invasive approaches for quantitative measurement of biomarkers in body fluids. Anchoring nanostructured materials on textile materials is key in designing wearable electrochemical sensing devices as the nanomaterials provide multi-faceted application including bioreceptor immobilization and signal transduction. In this work, SnO2 nanoflake-integrated conductive carbon fiber (SnO2/CCY) was explored for biosensing of cortisol. Cortisol is known as a stress hormone and plays crucial role in human physiology and immune system. Accurate detection of cortisol is crucial in personalized health monitoring and quantitative estimation of acute and chronic stress levels in humans. Anti-cortisol antibodies were immobilized onto the SnO2/CCY for improving the selectivity of the detection. The response of the electrochemical immunosensor towards cortisol binding was monitored using an electroactive redox probe (Fe(CN)63−/4−). The oxidation current of the redox probe (− 0.42 V vs. Ag/AgCl) was probed for creating sensor calibration plot. The electrochemical immunosensor responded to a broad range of cortisol concentration (10 fg/mL to 1 µg/mL) and showed a good detection limit (1.6 fg/mL) towards cortisol detection. Under optimized conditions, the immunosensor has been evaluated to measure cortisol levels in human sweat. The sensor results were correlated using commercial chemiluminescence immunoassay (CILA) method.