Sensing of human stress biomarkers using BODIPY-functionalized carbon nanoparticles

Stress affects many aspects of human functioning, and its effects on cognition are particularly relevant in high performance scenarios such as military operations and space missions. Dopamine, noradrenaline, and cortisol are key biomarkers associated with stress, anxiety, depression, and cardiovascular disease, yet their qualitative and quantitative detection usually requires lengthy laboratory analyses and lacks a single, selective one-pot method. In this work, we developed a fluorescent nanosensor based on carbon nanoparticles functionalized with a BODIPY-based fluorophore (CNPs-Ar-BDPy) for the detection and discrimination of dopamine, noradrenaline, and cortisol in aqueous solution. The sensing platform exploits the carbon nanoparticle core as a structural scaffold and the BODIPY moiety as a recognition site, enabling specific interactions with catecholamines and cortisol through hydrogen bonding between the BODIPY fluorine atoms and the OH and C=O groups of the analytes. The CNPs-Ar-BDPy were synthesized, functionalized, and fully characterized by UV Vis and fluorescence spectroscopy, and their sensing performance was evaluated in aqueous media using fluorescent titration and FT-IR. Selectivity was further assessed using multivariate analysis by PLS-DA, demonstrating effective discrimination among the three biomarkers. In addition, the role of the covalent linkage between the carbon nanoparticle core and the BODIPY unit was investigated, and the obtained apparent affinity constants were compared with those of analogous nanoprobes featuring a non-rigid, non-preorganized spacer. The rigid aryl linked BODIPY proved to enhance binding by about two orders of magnitude, highlighting the importance of structural preorganization and fluorescence continuity across the core fluorophore interface. The proposed nanosensor thus represents a promising tool for rapid, selective monitoring of stress related biomarkers.