Researchers at the University of California, San Diego (UCSD) said on the 28th that they developed a wearable sensor that automatically detects Parkinson's patients' medication doses from fingertip sweat, in the Proceedings of the National Academy of Sciences (PNAS).
Parkinson's patients must continue taking medication to avoid suddenly losing motor function. If the dose is too low, the treatment is ineffective, and if it is too high, side effects may occur, so the dose must be checked continuously. But because the check has relied only on the patient's memory, accuracy has inevitably suffered. Nor is it feasible to go to the hospital every day for blood tests.
The wearable sensor that sticks to a finger is not only convenient for patients to use, but its accuracy was similar to results obtained from hospital blood tests. The dose measured by the sensor is transmitted wirelessly to medical staff, enabling remote diagnosis. It opens the door to personalized treatment that adjusts drug doses for each patient.
◇ Tracking drugs that supplement dopamine
Parkinson's disease is a degenerative brain disorder first identified in 1817 by British physician James Parkinson. As nerve cells in the brain that secrete dopamine decrease, symptoms of motor impairment appear, such as trembling hands and feet and a shuffling gait. Dopamine is a neurotransmitter that finely controls body movements.
UCSD's Joseph Wang of the Department of Chemistry and Nanoengineering and Irene Litvan of the School of Medicine's Department of Neurosciences developed a sensor technology that detects levodopa, a Parkinson's treatment drug, in sweat. Once in the body, levodopa converts into dopamine, a neurotransmitter, to ease Parkinson's symptoms.
The fingertip patch developed by the researchers contains hydrogel, a jelly-like polymer material rich in moisture. Increasing the salt concentration of the hydrogel draws sweat from the pores at the fingertips. It uses osmosis, in which liquid moves from a lower to a higher concentration. The same principle explains why salting napa cabbage draws out moisture and wilts the leaves.
Sweat droplets drawn out by the hydrogel like a sponge travel through paper-made microchannels to the sensor. When the drug in the sweat reacts with enzymes on the sensor electrode, a tiny voltage is generated. A lower voltage indicates a lower drug concentration, and a higher voltage indicates a higher concentration. The sensor operates on the voltage it generates, so it needs no separate power source. However, a battery is required to wirelessly transmit the sensor's voltage changes to an external device.
◇ Simple yet as accurate as a blood test
The researchers developed a sensor to detect levodopa in the body because the proper dose varies by patient. If the dose is reduced too much, the patient cannot move, and if it is excessive, side effects such as convulsions occur. The dose must be checked continuously, but for now it is adjusted based on the patient's medication and symptom diary and a brief observation in the clinic. The fingertip patch can solve these problems.
The researchers tested the fingertip patch in three healthy people and four Parkinson's patients. In clinical trials, the fingertip patch determined levodopa levels in the body as accurately as blood tests that take days with specialized hospital equipment. It means Parkinson's patients can track drug levels in real time in daily life.
Both patients and healthy people showed individual differences in how fast the drug declined and in its half-life. The fingertip patch showed the potential to shift levodopa prescriptions—once reliant on patients' memories and symptom diaries—to personalized treatment based on objective, real-time data. However, the small clinical sample size is a clear limitation. The researchers noted that large-scale, long-term clinical trials are needed to reach the stage of determining actual doses with patch data or automatically administering the drug.
References
PNAS (2026), DOI: https://doi.org/10.1073/pnas.2610453123