One day, just a few tears may be enough to provide valuable insights into a person's neurological health. Researchers reporting in ACS Omega have developed a low-cost electrochemical sensor capable of detecting dopamine—a neurotransmitter involved in movement, learning, motivation, and emotional regulation. Tests using artificial human tear fluid showed that the device accurately measured dopamine across a clinically relevant range of concentrations. The technology could pave the way for new tools to monitor Parkinson's disease and other conditions associated with abnormal dopamine levels.

"By developing this sensor, we aimed to enable ultra-early detection of neurological disorders, allowing clinical intervention before the onset of major symptoms," said lead author Neftali Lenen Villarreal Carreño.

Changes in dopamine levels—whether too low or too high—are linked to a variety of neurological and psychiatric disorders. In Parkinson's disease, for example, dopamine levels decline. Current monitoring methods, such as blood or urine tests and implantable devices, can be time-consuming or invasive. Tears, however, offer a fast, painless, and non-invasive alternative for assessing health.

To create the sensor, the researchers used a laser to convert part of a thin plastic film into electrically conductive graphene. The postage stamp-sized device generates an electrical signal when dopamine interacts with the graphene surface.

During laboratory experiments, the team added dopamine to artificial human tears and evaluated the sensor's performance. The device accurately measured dopamine concentrations, including levels similar to those previously observed in the tears of people with Parkinson's disease. It also maintained its accuracy in the presence of other compounds commonly found in tears.

"Our sensor can detect dopamine concentrations that are significantly below normal or up to three times higher than normal," said co-author Lucas Minghini Gonçalves. "This capability allows us to identify the initial decline in dopamine levels at an early stage, which is crucial for timely therapeutic intervention."

According to the researchers, their findings lay the groundwork for future studies using human tear samples and could ultimately lead to the development of portable devices capable of monitoring neurological biomarkers through tear fluid.