Engineers and neuroscientists at the University of California San Diego have developed a soft, wearable fingertip patch that continuously tracks a patient's Parkinson's disease medication levels through their sweat. The device operates using chemicals in the patient's sweat - no batteries required. Its measurements were comparable to those obtained by standard laboratory blood tests.

The technology, published in Proceedings of the National Academy of Sciences, could enable doctors to precisely customize daily medication schedules for patients at home.

The patch monitors levodopa, the gold-standard drug for managing the loss of motor control caused by Parkinson's disease. Prescribing the right dose is challenging: reducing levodopa leaves patients unable to move, while too much triggers severe, uncontrollable jerking movements. Initially, the drug's effects can last several hours. But as the disease progresses, the therapeutic window narrows down to two hours. Currently, clinicians must rely on subjective patient diaries to adjust treatment. Unfortunately, these methods fail to catch dangerous dosing gaps.

The new wearable device offers a way to continuously track real-time concentrations of levodopa in the body. 

The research was led by study co-first author Tamoghna Saha, a postdoctoral researcher in the lab of Joseph Wang, professor in the Aiiso Yufeng Li Family Department of Chemical and Nano Engineering at the UC San Diego Jacobs School of Engineering. The engineering team developed the technology in joint collaboration with the lab of Irene Litvan, professor in the Department of Neurosciences at UC San Diego School of Medicine. 

The project is part of a longstanding collaboration between the Wang and Litvan teams to develop wearable levodopa monitors that can improve personalized care for people living with Parkinson's disease. 

The patch is worn on the fingertip, which is packed with a high density of sweat glands. The patch is equipped with a specially engineered absorbent gel that acts like a sweat sponge. The gel contains a highly concentrated mixture of salts and benign solvents - and that draws sweat out of the pores, since water naturally flows toward areas with higher salt concentrations.

When levodopa in the patient's sweat comes into contact with enzymes embedded in the patch, it triggers a chemical reaction, which in turn generates a small, measurable voltage. This chemical reaction is what powers the patch. The amount of voltage generated also serves as an indicator of the patient's levodopa level: lower voltage signals low levels, while higher voltage signals high levels. 

In clinical tests involving both healthy volunteers and patients with Parkinson's, the patch tracked levodopa levels as accurately as standard laboratory blood tests, which take days to return results. The data revealed that individuals with Parkinson's clear levodopa from their systems significantly faster than healthy individuals. This result explains why a patient's Parkinson's symptoms can deteriorate so suddenly, the researchers noted.

This technology lays the groundwork for a closed-loop system, where a levodopa monitoring patch could communicate with a pump to automatically deliver the precise doses of the drug right when the body needs it.

Source:

Journal reference:

A Wearable Patch for Continuous Levodopa Monitoring in Sweat: Towards Exertion and Power-Free Pharmacodynamic Assessment in Parkinson’s. Proceedings of the National Academy of Sciences. DOI: 10.1073/pnas.2610453123.