Researchers have developed a highly sensitive but low-cost method to detect dopamine, which may help in the early diagnosis of several disorders characterized by abnormal dopamine levels such as Parkinson’s disease, a study has found.
For the first time, the new detection method was able to measure dopamine in sweat, showing its potential to be part of portable, wearable technology to monitor dopamine levels in real-time.
The study, “Single-atom doping of MoS2 with manganese enables ultrasensitive detection of dopamine: Experimental and computational approach,” was published in the journal Science Advances.
Parkinson’s disease is caused by the impairment or death of nerve cells that produce dopamine — an important chemical messenger molecule in the transmission of nerve signals.
Abnormal dopamine levels also are associated with several other neurological disorders, including Alzheimer’s disease and schizophrenia, and as such, methods to measure dopamine levels may help with diagnosis.
While there are methods to detect dopamine, including urinalysis by lab testing, recent research has focused on developing non-invasive, low-cost, easy-to-use dopamine detectors that are highly sensitive and have a short response time.
“If you can develop a very sensitive, yet simple-to-use and portable, detector that can identify a wide range of dopamine concentration, for instance in sweat, that could help in non-invasive monitoring of an individual’s health,” Aida Ebrahimi, PhD, study co-author, said in a press release.
Ebrahimi, along with colleagues at Penn State University, and collaborators in New York, China, and Japan, chose to build a dopamine detector using a metal material that forms an ultra-thin, two-dimension layer called molybdenum disulfide (MoS2).
When a substance like dopamine binds to MoS2, it alters the electronic state of the material, which produces an electric signal that can be amplified and measured.
Metals such as gold can be added to improve the selective binding of dopamine and improve the sensitivity; however, given the costs and scarcity of these metals, it is necessary to find a lower-cost alternative.
In this study, the team added a more common, less-expensive metal called manganese (Mn) — known to react with dopamine — to the two-dimensional layers of MoS2, in a process known as single atom doping.
Manganese was added using a well-known, scalable method called electrodeposition (electroplating), which prepared the MoS2 for manganese doping.
“One challenge is to develop a scalable method to bridge fundamental studies and practical applications,” said Yu Lei, PhD, study co-lead, and doctoral candidate at Penn State. “Our method is based on electrodeposition, which has been widely used in industry, thus providing a scalable route to functionalize MoS2 in a scalable way.”
Testing showed that adding manganese to MoS2 improved the behavior toward dopamine. When mixed with ascorbic acid (vitamin C) and uric acid, two chemicals that coexist with dopamine in the central nervous system (brain and spinal cord) and serum, dopamine was selectively detected at different concentrations.
This is important “to selectively detect DA [dopamine] in the presence of these redox-active interferents,” the researchers wrote.
The Mn-MoS2 sensor achieved a low-end detection limit of 50 picomolar and was able to detect 50 nanomolar (nM) dopamine in artificial sweat and 5 nM dopamine in a solution of 10% blood serum.
“To the best of our knowledge, there are no reports on sensing [dopamine] in sweat despite the fact that many of the biomarkers found in blood are also found in sweat,” the researchers wrote.
The technique also supports the development of alternative non-invasive diagnostics with a goal to find other material combinations to detect a variety of different biomarkers, the scientists said.
“Our results provide the first step in demonstrating Mn-MoS2 as a low-cost sensitive material for non-invasive monitoring of [dopamine] levels in sweat using wearable technologies,” the researchers wrote.
“In future, we can envision a combined sensor/actuator that can detect the dopamine and provide therapy at the same time. The sensors can be integrated with miniaturized chips for integration of sensing, actuating, control and data processing,” Ebrahimi said.
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