A highly sensitive molecularly-imprinted electrochemical sensor based on a conducting PEDOT/SA hydrogel for the detection of cortisol with exceptional antifouling properties

Electrochemical biosensors offer a cost-effective and noninvasive approach for continuously monitoring cortisol in complex bodily fluids like blood, sweat, or saliva. However, their high sensitivity makes them vulnerable to biological contamination when used with biological samples. In this study, an electrochemical sensor was developed using an antifouling molecularly-imprinted hydrogel that combines the antifouling properties of a conducting polymer hydrogel with the recognition capabilities of a molecularly-imprinted polymer (MIP). The conductive hydrogel, composed of poly(3,4-ethylenedioxythiophene)/sodium alginate (PEDOT/SA), was synthesized through an electrochemical gelation technique. This hydrogel displayed a well-connected structure at the macroscopic level, leading to an increased effective surface area for the resulting electrochemical sensor. The MIP electrochemical sensor effectively minimized non-specific adsorption and demonstrated high sensitivity and selectivity in detecting trace amounts of cortisol in complex physiological fluids. Detection of the target analytes was accomplished using electrochemical impedance spectroscopy, with a linear range spanning from 10 –12 to 10 –8 M and a detection limit of 0.314 pM, as well as chronocoulometry, with a linear range from 10 –12 to 10 –7 M and a detection limit of 0.131 pM. The sensor showed commendable performance in accurately detecting cortisol in diverse bodily fluids such as saliva, sweat, and serum. By combining the MIP with a conductive hydrogel that resists biofouling, the electrochemical sensor exhibited high specificity, sensitivity, and exceptional resistance to interference when used in practical biological applications.