Reagent-Less Low-Concentration Cortisol Detection Enabled by Laser-Induced Graphene Electrodes

Electrochemical sensors are crucial for medical diagnostics and on-body biomarker monitoring due to their high sensitivity, low cost, and miniaturization capability. This study presents a novel reagent-less molecularly imprinted polymer (MIP)-based cortisol sensor using a laser-induced graphene (LIG) electrode. The LIG electrodes were fabricated by converting polyimide substrates with a CO2 laser and modified with Prussian Blue (PB) stabilized by Nickel Hexacyanoferrate (NiHCF). The high surface area and porosity of LIG enhanced the stability and adhesion of PB nanoparticles, leading to exceptional redox signal stability in 0.1 M KCl. Compared to a conventional screen-printed carbon electrode (SPCE), the LIG-based sensor exhibited higher sensitivity, a lower limit of detection (173.3 pM), and a wider dynamic range (1 nM - 100 μM) for cortisol detection, as demonstrated by square wave voltammetry (SWV). The LIG sensor effectively detected cortisol at 1 nM below the physiological range, suitable for real-time stress monitoring and medical diagnostics. This study highlights LIG as a superior transduction material, enhancing the MIP-based sensors' capability to detect low-concentration analytes. The findings offer a cost-effective and scalable approach for advanced biosensing applications.