Impedimetric Biosensor Based on Functionalized Borophene Nanosheets for Cortisol Diagnosis in Serum Biofluid

Cortisol, a stress biomarker, is released substantially into the bloodstream upon exposure to physiological and psychological stress. Delays in its detection can contribute to the onset and progression of various diseases, largely due to the lack of portable, rapid, and economical diagnostic tools. Addressing this challenge, we developed an electrochemical cortisol biosensor using amine-functionalized borophene nanosheets (NH 2 –BRPH) for the direct detection of cortisol at clinically relevant concentrations. NH 2 –BRPH nanosheets were synthesized via aminosilanization of BRPH nanosheets and subsequently deposited onto the surface of an indium tin oxide (ITO) electrode through electrophoretic deposition. Further, anti-CORT antibodies were covalently conjugated using EDC-NHS conjugation and then treated with BSA to avoid nonspecific binding, resulting in the successful development of the cortisol biosensor (BSA/anti-CORT/NH 2 –BRPH/ITO). Here, EIS was employed as the electroanalytical technique for the cortisol sensing study. The developed biosensor has a wider detection range of 1–960 ng mL –1, with a sensitivity of 0.184 Ω mL ng –1 cm –2, and offers a LOD of 1.0 ng mL –1 . Furthermore, the biosensor demonstrated excellent reproducibility, low interference, and stability exceeding 56 days under a controlled environment. The performance of the developed sensor was also investigated in serum biofluid, demonstrating a strong correlation with the standard samples.