Engineers at the University of California, San Diego, have developed a mouth guard that monitors health markers, such as lactate, cortisol, and uric acid, in saliva. The information can then be wirelessly transmitted to a smartphone, laptop, or tablet.
The UC-San Diego proof-of-concept device can be used to non-invasively monitor patients' health, athletes’ performance, and soldiers' or pilots' stress levels.
In a study, engineers focused on uric acid, which is a marker related to diabetes and to gout. Currently, the only way to monitor the levels of uric acid in a patient is to draw blood.
The university team created a screen-printed sensor using silver, Prussian blue ink, and uricase, an enzyme that reacts with uric acid. Because saliva is extremely complex and contains many different biomarkers, the researchers needed to make sure that the sensors only reacted with the uric acid.
Nanoengineers set up the chemical equivalent of a two-step authentication system. The first step is a series of chemical keyholes, which ensures that only the smallest biochemicals get inside the sensor. The second step is a layer of uricase trapped in polymers, which reacts selectively with uric acid. The reaction between acid and enzyme generates hydrogen peroxide, which is detected by the Prussian blue ink.
The information is then transmitted to an electronic board as electrical signals via metallic strips that are part of the sensor. The electronic board uses small chips that sense the output of the sensors, digitizes the output, and then wirelessly transmits data.
Researchers collected saliva samples from healthy volunteers and spread them on the sensor, which produced readings in a normal range. Next, they collected saliva from a patient who suffers from hyperuricemia, a condition characterized by an excess of uric acid in the blood. The sensor detected more than four times as much uric acid in the patient’s saliva than in the healthy volunteers.
The ability to monitor continuously and non-invasively saliva biomarkers holds considerable promise for many biomedical and fitness applications.