TE24 Health Desk:
Imbalances in brain chemistry are at the heart of many neurologic diseases. These same brain chemicals also play roles in gut health. So, scientists at Stanford have invented “NeuroString”—a soft implantable probe that can interface seamlessly with both brain and gut tissue. They describe the probe in a paper published June 2, 2022 in Nature. It has potential applications in depression, Parkinson’s disease, and intestinal diseases.
“The standard way individuals are attempting to comprehend the mind is to peruse and record electric signs,” says Jinxing Li, the paper’s most memorable creator. “Yet, synthetic signs assume similarly as critical a part in cerebrum correspondence, and they are additionally straightforwardly connected with sicknesses.” Li began and played out the work as a postdoc in Zhenan Bao’s lab in Stanford’s Department of Chemical Engineering; he is presently an associate teacher of biomedical designing at Michigan State University.
NeuroString estimates dopamine and serotonin, two compound couriers that adjust electrical signs in neurons. Dopamine is most popular for its job in the cerebrum’s prize framework; serotonin is the objective of antidepressants like Prozac. Both are likewise engaged with development, rest, craving, and assimilation.
Inserts that action dopamine and serotonin as of now exist, yet they are made of unbending carbon bars encased in glass tubes. “Those are extremely unbending tests. They are extremely fragile,” Li says. Besides the fact that the embed break can, it additionally abrades against the soft tissue in the cerebrum, which can kindle synapses and corrupt the embed.
Bao’s lab designed a delicate test. “My gathering has been making delicate hardware for a long while,” says Bao, the K. K. Lee Professor and seat of the Department of Chemical Engineering in the Stanford School of Engineering. The test is made of graphene, a type of carbon that is molecularly slender. Bao’s group utilized a laser to etch what Li depicts as a “shaggy snared organization of graphene” into a plastic. The plastic contains particles that transform into nanoparticle spots on the outer layer of graphene that can work on the responsiveness and selectivity for synchronous estimation of dopamine and serotonin. The specialists then, at that point, implanted the organization in an elastic network.
“Graphene itself isn’t entirely stretchable however in the event that it is entrapped as a cross section and implanted in an elastic, it becomes stretchable,” Li makes sense of.
Bao adds, “It’s like a kirigami. On the off chance that you cut designs into and, you can extend it, you see some sort of empty associated paper organization. It’s exactly the same thing here, yet the organization is made of graphene sheets.” NeuroString has a similar delicateness as natural tissue. “The sensor is delicate and flexible, similar to an elastic band, which doesn’t cause harm when embedded into the mind or the stomach, which isn’t just delicate yet in addition continually moving,” Bao says.
To test the probe, Bao’s team collaborated with Stanford scientists from biology, psychiatry, gastroenterology, and surgery. “I think that’s the most privileged part of Stanford: It is quite open and collaborative,” Li says.
In one experiment, the team implanted NeuroString into the brain and gut of the same mice. When they fed the mice chocolate syrup, NeuroString detected spikes of dopamine in the brain and spikes of serotonin in the gut—both expected responses to chocolate. Dopamine is made in the brain, whereas serotonin is mostly made in the gut. In another experiment, NeuroString detected distinctive patterns of gut serotonin in mice with gut inflammation compared with healthy mice.
“The first time we saw the signal from the probe was a eureka moment,” says co-author Xiaoke Chen, associate professor of biology. “Chronic recording of dopamine and serotonin signals in freely moving animals is a dream experiment that we always wanted to do. And with this beautiful collaboration, we were able to make it happen.”
The implanted mice behaved and ate normally and had normal bowel movements. “The exciting thing about the tool was that it did not seem to disrupt the normal function of the tissue,” says co-author Aida Habtezion, professor of medicine. This means that the implant could someday be used for real-time monitoring in humans, akin to a smartwatch, but able to track biochemical levels rather than heart rate or steps, she says. Habtezion is currently on a leave of absence and serving as the Chief Medical Officer of Pfizer, but contributed to the work while she was still at Stanford.
Tracking serotonin levels in the gut could be useful in diagnosing and monitoring intestinal diseases such as irritable bowel syndrome. Tracking dopamine levels in the brain could be useful in Parkinson’s disease, which is caused by a lack of dopamine. One of the treatments for Parkinson’s disease, deep brain stimulation, works in part by stimulating neurons to produce more dopamine. If deep brain stimulators could be paired with NeuroString, this would allow doctors to precisely control the amount of dopamine released.
The implant is not yet ready for clinical use. For one thing, the probe is still attached to wires that read out the signals; a wireless version would be needed for use in people. In the meantime, the probe has many uses in research. For example, antidepressants like Prozac work by modulating serotonin levels, which may explain why they sometimes cause gastrointestinal side effects, Chen says. “We now have the tool to allow real-time monitoring of the impact of those drugs on serotonin fluctuation in both the brain and gut in mouse models.”
He adds, “Now that we’ve shown that the probe works, there’s a very long list of biological questions we want to tackle.”
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