A Novel Cortisol Biosensor Based on the Capacitive Structure of Hafnium Oxide: Application for Heart Failure Monitoring

Assessing cortisol level in human bodies has become an essential tool to recognize heart failure (HF). In this work, the label-free detection of cortisol using a novel capacitive substrate based on hafnium oxide (HfO
₂
) was accomplished. In this context, the interaction between the cortisol with its corresponding polyclonal antibody (pAb) has been studied, and the detection event was followed by electrochemical impedance spectroscopy (EIS). Cortisol was detectable between a wide range of concentration from 2 ng/mL to 50 ng/mL. Moreover, the cross-selectivity study showed that the developed biosensor demonstrated to be highly selective toward cortisol when compared to some related biomarkers such as Tumor Necrosis Factor (TNF-α) and N-terminal pro B-type Natriuretic Peptide (NT-proBNP). To the best of our knowledge, this is the first biosensor that has been based on capacitive HfO
₂
for cortisol detection by EIS.