Over time, stress and anxiety can build to a point where life’s challenges become overwhelming and cause physical effects. Now, in ACS Applied Materials & Interfaces, researchers report a dental floss pick with a built-in sensor that could monitor stress as part of a daily routine. The device, which accurately senses levels of the stress hormone cortisol in minutes, could help users recognise when it’s time to get help.

Unchecked chronic stress can lead to health conditions such as heart disease and mental disorders. Catching rising stress levels early is important, but daily blood tests at a doctor’s office aren’t feasible for most people, and self-reported questionnaires are subjective. That’s why researchers are developing point-of-care tests that measure cortisol levels in saliva, which mirror the hormone’s concentrations in blood.

Although the saliva tests are promising, many of them require people to remember to perform the complicated analyses or use a bulky mouthguard. In addition, the anxiety of performing a test can cause stress levels to spike. So, Sameer Sonkusale and colleagues took a completely different approach by integrating a cortisol sensor into a dental floss pick — something many people use every day.

The team’s dental pick features floss that collects saliva. The floss is connected to a microfluidic thread that transports saliva to a flexible electrochemical sensor embedded in the handle of the pick. The sensor is made of an electrode with an electropolymerized molecularly imprinted polymer (eMIP) on it. The researchers made the eMIP by embossing cortisol molecules into an electrically conductive film and then removing them, similar to a shoe leaving an impression in wet cement.

During tests, salivary cortisol binds in the impressions, decreasing the electrical current flowing through the sensor, which produces a signal that is wirelessly transmitted to a mobile device. The strength of the signal corresponds to the amount of cortisol in the saliva. Finally, the analysed saliva moves to an adsorbent waste pad next to the sensor, and the pick can be discarded.

The device takes around 10 minutes to report a result. In tests with cortisol-spiked artificial saliva, the dental pick was sensitive enough to detect small increases in cortisol that could be early indicators of stress. In tests with real human saliva samples, the dental flosser performed just as well as the commonly used ELISA saliva test for measuring levels of cortisol.

Overall, the researchers say that this device is one of the best-performing cortisol sensors reported so far, and it could someday be modified to detect other clinically important salivary molecules.