TiO2/CuInS2-sensitized structure for sensitive photoelectrochemical immunoassay of cortisol in saliva

Cortisol, a steroid hormone, has been confirmed as a kind of biomarker that reflects the stress response of psychobiology and related adverse health outcomes. Therefore, a sensitive and selective non-invasive assay to detect cortisol is needed. In this work, we developed a new photoelectrochemical immunosensor for determining cortisol levels in human saliva, based on evident photocurrent of the low-toxic CuInS2 quantum dots (CIS QDs) immobilized on the surface of TiO2 and significant signal amplification of the CdS/melamine network as a label. The photocurrent depended on the amount of label competing with cortisol antigen to bind the antibody on the electrode. The photocurrent decreased with the increment of cortisol concentration. Under the optimal conditions, this cortisol biosensor exhibited a broad linear range (0.01-100 ng/mL) with a low detection limit (7.8 pg/mL). Moreover, the methodology was implemented with good stability and high repeatability.

Automated summary

A new photoelectrochemical immunosensor was developed in this study for non-invasive detection of cortisol levels in human saliva. The method showed high sensitivity and selectivity, with a broad linear range and low detection limit.