Saliva-Sensing Dental Floss: A Novel Tool for Assessing Daily Stress via On-Demand Salivary Cortisol Measurement Integrating Molecularly Imprinted Polymer and Thread Microfluidics

Abstract

Elevated stress negatively impacts health, increasing the risk of cardiovascular diseases, weak immunity, anxiety, and cognitive decline. Current lab-based methods lack real-time stress measurement, while saliva diagnostics offers a convenient and non-invasive alternative. This work proposes repurposing dental floss as a thread-analytical saliva diagnostic device. This method uses flossing to collect and transport saliva to a flexible electrochemical sensor via capillary microfluidics, where cortisol, a stress biomarker, is measured. By integrating an electropolymerized molecularly imprinted polymer specific to cortisol (cort-eMIP) on a porous-laser-engraved-graphene (PLEG) working electrode, the saliva-floss platform shows a detection range of 0.10-10000 pg mL-1 (R2 = 0.9916) with a detection limit of 0.023 pg mL-1 for cortisol (in buffer medium). The saliva-sensing dental floss provides results within 5 minutes. The thread-based microfluidic design minimizes interference and ensures consistent repeatability when testing artificial and actual human saliva samples, yielding 98.64 to 102.4 percent recoveries with a relative standard deviation of 5.01%, demonstrating high accuracy and precision. Validated using human saliva samples in a stress study, it showed a high correlation (r= 0.9910) with conventional ELISA assays. Combined with a wireless readout, this saliva floss offers a convenient way to monitor daily stress levels and can be extended to detect other critical salivary biomarkers.