Molecularly imprinted polymer wearable biosensing of cortisol in sweat for mental stress evaluation

Accurate detection of cortisol levels is crucial for stress management and the diagnosis of hypothalamic-pituitary-adrenal axis disorders. Current methods rely on invasive serum tests or immunosensors with complex procedures and are expensive. Here, we developed a molecularly imprinted polymer (MIP)-based electrochemical sensing system for label-free detection of cortisol in sweat, in which polypyrrole exhibited selective recognition of cortisol via hydrogen bonding, and prussian blue (PB) was embedded into the MIP as the redox probe. By optimizing parameters including the template, monomer, modification time, and excitation current, the MIP exhibited strong affinity for cortisol with an imprinting factor (IF) value of 7.7. The MIP sensors' sensitivity is also significantly enhanced, showing a wide linear range from 50 to 500 ng/mL, with the LOD and LOQ at 15.21 ng/mL and 46.09 ng/mL. The fully integrated system employs a flexible electrode for real-time cortisol analysis and enables wireless data transmission via circuitry and smartphones. Human sweat analysis was conducted in scenarios involving circadian rhythms and ice-water stimulation. The results were consistent with literature findings and validated the sensor's high accuracy compared to the gold standard measurement method. The proposed novel MIP sensing platform opened compelling possibilities for non-invasive stress tracking, offering significant potential for personalized stress prevention to achieve precision health protection.