Fabrication of N-doped multidimensional carbon nanofibers for high-performance cortisol biosensors

Abstract Cortisol, a stress biomarker, is an important hormone that regulates blood pressure, glucose levels and carbohydrate metabolism in humans. Abnormal secretion of cortisol can cause various symptoms and diseases closely linked to psychological and physical health. In this study, high-performance, field-effect transistor (FET)-based biosensors for cortisol detection were fabricated from large surface area, N-doped multidimensional carbon nanofibers. Biosensor morphology was controlled by tailoring the pressure conditions during vapor deposition polymerization (VDP). Thereafter, conductive channels in the FET were completed by thermal annealing, acid treatment, and antibody attachment. Changes associated with chemical processes were characterized by Raman spectroscopy, Fourier transform infrared (FT-IR) spectroscopy, X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM). The resulting transducers exhibited electron transport at the liquid-ion gate of the FET, resulting in a rapid response toward cortisol molecules with accurate selectivity, stable reusability, and high sensitivity. Limits of detection were as low as 100 aM with a wide linear detection range of 100 aM -10 nM due to the large surface area of the transducer and a correspondingly high number of antibody labels. The response and applicability of these cortisol biosensors were also assessed using saliva as a test matrix.