Electrochemical Immunosensing of Saliva Cortisol

The detection of cortisol in saliva is an important screening tool for psychological stress and health monitoring, including the diagnosis of Cushing's syndrome, Addison's disease, and post-traumatic stress disorder (PTSD). In this work, a simple, low-cost, label-free, electrochemical immunosensing platform is explored for highly sensitive and selective detection of cortisol in saliva. Anti-Cortisol antibodies (Anti-C ab ) covalently immobilized on self-assembled monolayer (SAM) of dithiobis(succinimidylpropionte) (DTSP) modified microfabricated interdigitated microelectrodes (IDEs) were used for electrochemical detection of cortisol. The non-binding sites of immunosensor surface were blocked using ethyleneamine (EA). Electrochemical response studies as a function of cortisol concentrations were conducted using cyclic voltammetry (CV). The sensor exhibited a detection range from 10 pg/mL to 100 ng/mL, a detection limit of 10 pg/mL, and a sensitivity of 6 μA/(pg/mL) with the regression coefficient of 0.99. The obtained sensing parameters were in physiological range. The sensor was successfully tested on multiple specimen samples of saliva collected at different time intervals from two participants. The obtained cortisol concentrations from the developed electrochemical system correlate well with those were obtained using ELISA.