Development of Molecularly Imprinted Conducting Polymers for Stress Biomarker Cortisol Detection

Psychological stress is linked to various health conditions such as autoimmune disorders, cardiovascular diseases, and mental illnesses, often mediated by elevated levels of cortisol, a stress-associated glucocorticoid hormone. High chronic cortisol levels are implicated in diseases like Cushing syndrome and Addison's disease, highlighting the importance of measuring cortisol for stress management and clinical diagnosis. Existing detection methods, such as electrochemical immunosensors and enzyme-linked immunosorbent assays (ELISA), encounter limitations related to cost, stability, and scalability. To address these issues, we developed an electrochemical sensor using molecularly imprinted polymers (MIPs) for sensitive and selective cortisol detection. Utilizing functional monomer-target interactions without additional additives is also a cost-effective approach. Two conducting polymers, aniline and ortho-phenylenediamine (o-PD), were used and evaluated for their ability to form selective binding sites through electropolymerization to investigate the influence of monomer structure on imprinting efficiency. The resulting molecularly imprinted conducting polymer (MICP)-based sensors demonstrated a limit of detection (LoD) of 5.8 pM, which is more than three orders lower than the typical cortisol concentration in human fluid. The sensor's selectivity was confirmed in human fluids, and its practicality was validated through saliva testing, with results comparable to those of ELISA-based sensors. These findings suggest that MIP-based sensors offer a stable, cost-effective alternative for cortisol detection with potential applications in both clinical and high-stress environments.