These tiny sensors, which can track dopamine in the brain for more than a year, will be invaluable in monitoring patients with Parkinson's disease and other neurological diseases. It is an “invention” by a team from the Massachusetts Institute of Technology (MIT) and a feat, because these sensors can remain in place for several months. Monitoring dopamine levels could help doctors deliver stimulation or treatment more selectively, and only when needed.
Dopamine, a signaling molecule used throughout the brain, plays a major role in regulating our mood and controlling movement. Many disorders, including Parkinson's disease, depression and schizophrenia, are linked to dopamine deficiencies. By designing this new means of measuring dopamine in the brain for more than a year, the researchers also hope, beyond the opportunity to better assess the response to treatments, to learn more about the role of dopamine in healthy and diseased brains. “Until then, it was impossible to follow the evolution of its levels, in particular with the clinical evolution of the associated medical conditions”, explains Ann Graybiel, professor at MIT and member of the McGovern Institute for Brain Research. .
Track dopamine over the long term:Dopamine is one of many neurotransmitters that neurons in the brain use to communicate with each other. Traditional systems measuring dopamine-carbon electrodes with a diameter of about 100 microns can only be used reliably for about a day because they induce scar tissue that interferes with the ability of the electrodes to interact with dopamine. . The duration of follow-up was therefore the real challenge for the MIT team. The team designed these tiny sensors about 10 microns in diameter and were able to implant up to 16 of them to measure dopamine levels in different parts of patients' striatum. The main goal was indeed to operate the sensors over a long period of time while "retrieving" daily data on dopamine levels. The challenge was to avoid any immune reaction, in order to avoid the scar tissue that interferes with the accuracy of the readings.
These tiny sensors are virtually invisible to the immune system , even over long periods of time. After implantation of the sensors, populations of microglia (immune cells that respond to short-term damage) and astrocytes, which respond over longer periods of time, are found to be unchanged and similar to that of non-implanted brain tissue. The demonstration is carried out in animals, with 3 to 5 sensors per animal, to a depth of about 5 millimeters, in the striatum. Readings were taken weekly, after stimulating the release of dopamine from the brainstem, which travels to the striatum. This is the first proof of concept of sensors that can operate for more than a few months.
One obvious application: monitoring Parkinson's disease: If developed for use in humans, these sensors could be useful for monitoring patients with Parkinson's disease, especially those receiving deep brain stimulation . This treatment involves implanting an electrode that delivers electrical impulses into a deep structure of the brain. Using a sensor to monitor dopamine levels could help doctors deliver stimulation more selectively, only when needed. Then other sensors could be developed to measure other critical neurotransmitters in the brain.