A tiny, touch-based sensor uses sweat to detect the level of lithium in the body. Credit: Jialun Zhu and Shuyu Lin
Key Points:
- Current options for monitoring medication use have significant drawbacks, including invasiveness, accuracy and time.
- Scientists designed a tiny, touch-based sensor that uses sweat to detect the level of lithium in the body in 30 seconds.
- The technology could be the basis for other touch-based sensors.
Lithium can alleviate the symptoms of bipolar disorder and depression—if taken in just the right amount. Too little won’t work, while too much can bring on dangerous side effects. To precisely monitor the amount of this medication in the body, patients must undergo invasive blood tests.
Now, scientists presenting at the fall meeting of the American Chemical Society, report the invention of a tiny sensor that detects lithium levels from sweat on the surface of a fingertip in as little as 30 seconds, without a trip to the clinic.
Sweat can be difficult to use as a diagnostic fluid as it is only present ion minute amounts. While that may work for some biomarkers, the electrochemical sensing needed to detect charged particles of lithium requires a more aqueous environment. To provide it, the team engineered a water-based gel containing glycerol.
To trap the lithium ions after they traversed the gel, the research team used an ion-selective electrode. The accumulating ions generate a difference in electrical potential compared with a reference electrode. The researchers used this difference to infer the concentration of lithium present in sweat. Together, these components comprise a tiny, rectangular sensor that is smaller than the head of a thumbtack and can detect lithium in about 30 seconds.
After success using the sensor on an artificial fingertip, the team recruited volunteers to test it, including one person on a lithium treatment regimen. The scientists recorded the person’s lithium levels before and after taking the medication. They found that these measurements fell close to those derived from saliva, which prior research has shown to accurately measure lithium levels.
In future research, the team plans to study the effects of lotion and other skin products on the sensor’s readings. Additionally, Sam Emaminejad, the project’s principal investigator, who is at UCLA, is developing similar touch-based sensors to monitor alcohol and acetaminophen, among other substances. The complete sensing systems would then include additional features, such as encryption secured by a fingerprint, or—for substances like opioids prone to abuse—a robotic dispensing system that releases medication only if the patient has a low level in their bloodstream.
Information provided by ACS.