MnO2 cacti-like nanostructured platform powers the enhanced electrochemical immunobiosensing of cortisol

Abstract

Herein, we describe a label-free transition metal oxide based biosensor platform to detect both saliva and sweat cortisol levels at a point-of-care testing (POCT) perspective. The immobilization of ACAs on GCE/β-MnO2 CNs electrode is conducted by electrostatic interaction approach via isoelectric-point (IEP) of β-MnO2 (7.30) and cortisol antibodies (4.50), which establish a suitable atmosphere for effective immobilization. Bovine serum albumin (BSA) was served as blocking-agent for non-specific adsorption on the surface of MnO2 nanostructured electrode. Under optimized conditions, ACAs/beta-MnO2 cacti-like nanostructured (β-MnO2 CNs) electrode specifically interacted with cortisol molecules, which enabled rapid and sensitive electrochemical impedance detection of cortisol via 3D analyte diffusion profile at the electrode interface and also enhanced cortisol capture achieved by large specific surface of MnO2 nanostructures. This ACAs/β-MnO2 nanostructured electrode shows wide-linear EIS signals from 0.1 pM to 1500 pM with a limit of detection (LOD) of 0.023 pM (S/N = 3) and displays rapid binding kinetics with cortisol versus other glucocorticoids in terms of selectivity. Finally, the cortisol detection in human sweat, and saliva samples has been demonstrated for practical applicability and obtained results were compared with ELISA method.