Detection of Biomarkers for Human Health Monitoring Using an Easy-to-Use Array Sensor Based on Fluorescent Organic Molecules in Human Saliva

Monitoring stress biomarkers (dopamine, norepinephrine, adrenaline, and cortisol) and renal function indicators, like creatinine, in biological fluids, such as saliva, is crucial for non-invasive medical diagnostics. This work presents a portable, array-based sensor device designed for point-of-care (PoC) applications, combining ease of use, versatility, and on-site analysis capability. The system operates via optical output using fluorescent chemical probes—BODIPY, naphthalimides, and rhodamine—selected for their spectral properties and ability to interact with target analytes through non-covalent interactions. Probe–analyte interactions were tested in the solid state using an optical fiber to directly acquire fluorescence emission spectra. After validation in an aqueous solution, the device successfully detected dopamine, cortisol, adrenaline, and creatinine in real saliva samples. The system delivers quantitative results in under 40 minutes, with a detection limit in the pM range, and enables clear discrimination between cortisol, dopamine, and adrenaline. Thanks to its compact design and compatibility with smartphones or portable optical fibers, it allows rapid, real-time data acquisition without complex sample preparation or specialized personnel. The procedure includes 1) calibration in water; 2) calibration in artificial saliva; 3) measurements on real saliva; and 4) validation against ELISA. By relying on chemometric interpretation of fluorescence patterns from cross-reactive probes, the device avoids signal amplification, minimizing false positives. With a cost of approximately 5 EUR per test and no need for sample pre-treatment, it offers a cost-effective, scalable solution for clinical settings.