Immuno-Graphene Field-Effect Transistor-Based Cortisol Bioelectronics Using a Novel Cortisol Antibody

Cortisol plays an important role as a stress biomarker in human biological fluids, affecting the blood pressure, glucose levels, carbohydrate metabolism, and immune response mechanisms. Increased cortisol levels cause various diseases, including obesity, diabetes, hypertension, chronic fatigue, menstrual irregularity, and increased appetite. Moreover, mental healthcare can be controlled by controlling cortisol levels. Herein, an immuno-graphene field-effect transistor (IGFET) bioelectronic for cortisol detection was developed using a side-gate FET system based on the conjugation of a novel cortisol scFv-Fc antibody (Ab), produced from M13 bacteriophage display method, via oligo(phenylene-ethynylene)amine (OPE) interfacial chemical. The improved performance was obtained from the increased binding affinities between Ab and cortisol and the enhanced carrier mobility via formation of covalent bonds between OPE and graphene, and the IGFET bioelectronics showed excellent sensing performance with a limit of detection of 500 fM, a sensing monitoring range from 500 fM to 100 nM, a rapid detection time of 20 s, and a high-selective detection that enabled the detection of 10³ times lower cortisol concentrations than those of interference substances. In addition, the cortisol detection and monitoring were evaluated using artificial sweat, achieving similar performance to that of standard detection monitoring. Based on the results, this IGFET bioelectronics can be utilized to the stress-related assistance indicator and for the rapid observation of changes in cortisol levels.