Non-invasive electrochemical immunosensor for sweat cortisol based on L-cys/AuNPs/ MXene modified thread electrode

Thread-based electrochemical immunosensor is fabricated for non-invasive detection of cortisol in sweat by immobilization of anti-cortisol on L-cys/AuNPs/MXene modified conductive thread electrode. MXene and AuNPs increase the surface area of conductive thread electrode and facilitate anti-cortisol immobilization leading to enhanced sensor sensitivity. Anti-cortisol is immobilized on L-cys/AuNPs/MXene modified electrode by using 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide and N-hydroxysulfosuccinimide coupling agents. The electrochemical detection of cortisol is based on the decrease of oxidation current towards the antigen-antibody binding interaction owing to blocking of electron transfer process by cortisol. Under the optimal conditions, this immunosensor offers high sensitivity, a wide linearity of 5-180 ng mL^-1 and a detection limit of 0.54 ng mL^-1 with negligible effect from interferences. Furthermore, this immunosensor provides high reproducibility and long-term storage stability (≥6 weeks). Ultimately, this system is successfully applied for the detection of cortisol in artificial sweat with satisfactory results. Hence, this platform might be suitable to apply as a wearable electrochemical sensor for sweat cortisol by integrating on a wristband.