Hybrid BSA-PEO Nanofibers as a Stable Biointerface for Electrochemical Cortisol Immunosensing

The long-term stability of antibody immobilization remains one of the key limitations of electrochemical cortisol immunosensors. Herein, a hybrid bovine serum albumin-poly(ethylene oxide) (BSA-PEO) electrospun nanofiber matrix was employed as a stable and biocompatible platform for antibody immobilization and electrochemical cortisol detection. The nanofibrous biointerface was deposited directly onto Platinum (Pt) and gold (Au) electrodes, followed by anti-cortisol antibody immobilization and blocking. Structural and electrochemical characterization confirmed the formation of a homogeneous and highly functionalized sensing layer. The resulting immunosensors exhibited linear responses in the ranges of 0.1-15 μM (Pt) and 0.01-200 μM (Au), with the gold-based platform achieving a detection limit of 0.01 μM. High selectivity toward cortisol and satisfactory recoveries in human serum were obtained for both systems. Notably, the nanofiber matrix effectively preserved antibody activity and sensor performance, providing signal retention of 92.0% and 97.9% after 14 days for platinum- and gold-based immunosensors, respectively. These findings highlight the critical role of biointerface design in electrochemical immunosensing and demonstrate the potential of BSA-PEO nanofibers as stable immobilization matrices for cortisol monitoring in point-of-care and wearable applications.