Triple-enhancement of electropolymerized MIP on laser-induced graphene for point-of-care monitoring of sweat cortisol

Continuous, accurate, and stable detection of the steroid hormone cortisol is essential for evaluating and managing human physiological and psychological states. This study presents a wearable stress monitoring device (WSMD) that integrates gold nanoparticle (AuNP) modified Laser-Induced Graphene (LIG) with a custom low-power electronic system for wireless real-time cortisol monitoring. Precise control of gold nanoparticle (AuNP) growth on LIG via electrochemical deposition facilitated adhesion of the electropolymerized polypyrrole (PPy) MIP layer onto the electrode surface and enhanced embedment of Prussian blue (PB) as a built-in redox probe. This process endowed the fabricated flexible sensor with triple enhancement in electrochemical active surface area (ECSA), surface roughness, and redox activity, enabling a broad cortisol detection range of 1 pM to 100 µM (R² = 0.996) with high sensitivity (2790 nA/lg(C(nM))), reproducibility, and regenerability. ELISA validation confirms that WSMD enables real-time detection of cortisol concentrations in sweat samples in vitro, offering a feasible solution for daily stress monitoring.