Dopamine is a signaling molecule or neurotransmitter that is known to help control emotions. Dopamine levels are also a biomarker of certain diseases. Researchers have now developed a rapid test that can detect the levels of dopamine in a blood sample, without special processing on that sample. It works with an optical sensor that could become a cheap and effective screening tool for some types of cancer and neurological disease. The work has been reported in Science Advances.
"This plasmonic biosensor is extremely sensitive to low concentrations of biomolecules, which makes them a promising platform for specialized assays and point of care applications in remote locations," said senior study author Professor Debashis Chanda of the University of Central Florida NanoScience Technology Center, among other appointments. "In this work, we demonstrated an all-optical, surface-functionalized plasmonic biosensing platform for the detection of low concentrations of neurotransmitter dopamine directly from diverse biological samples, which includes protein solutions, artificial cerebrospinal fluid, and unprocessed whole blood."
Neurotransmitters serve many crucial functions, and although dopamine is sometimes known as a 'pleasure molecule,' it is thought to have an essential role in nearly all cognitive functions, including learning, motivation, and motor control. Dopamine and its receptors are known to have a role in Parkinson's disease, some neuropsychiatric disorders such as Tourette's Syndrome and schizophrenia, and could be influential in some autoimmune diseases. Because dopamine is also found at high levels in the gastrointestinal tract, it may relate to various bowel disorders including inflammatory bowel diseases as well.
Chanda noted that abnormal dopamine levels could also serve as biomarkers of some cancers. But we need reliable and precise ways to measure dopamine before we can use dopamine levels to diagnose disease. This effort may help scientists reach those goals.
Instead of a detection system like an enzyme or antibody that is attached to a molecule that changes color, this device relies on an aptamer, or DNA molecule, to detect dopamine. It is meant to identify dopamine in blood samples that have not been altered or prepared in any way. The scientists coated a sensor's active area with the aptamer, which can specifically and accurately identify a target molecule, which is determined by the aptamer's sequence.
This plasmonic sensor is made of a small gold pattern that triggers wave-like movements from electrons called plasmons, and the researchers used an optical setup to boost their strength. As a new molecule reaches the aptamer-coated sensor, the plasmon movement changes, affecting light reflection from the sensor. This can reveal the presence of the molecule.
These so-called plasmonic aptasensors could become highly accurate ways of monitoring disease, the study authors suggested.
"There have been numerous demonstrations of plasmonic biosensors but all of them fall short in detecting the relevant biomarker directly from unprocessed biological fluids, such as blood," noted first study author Aritra Biswas, PhD.
"This concept can be further explored in the detection of different biomolecules directly from unprocessed blood, such as proteins, viruses, DNA," added Chanda. "There may be great interest in developing countries where access to analytical laboratories is limited."
