MIT senior Christina Tringides demonstrates the technique used to create the fiber implants. (via MIT)
Neural implants have a lot of potential in brain medicine, and their development has many exciting implications in the treatment of neurological disorders such as Parkinson’s, a disease in which dopamine-secreting neurons inexplicably die. The main advantage of these implants is their ability to communicate with brain cells; however, previous attempts at neural probes have resulted in damage to the surrounding brain tissue due to the probes’ inflexibility and relatively large size. Worse, if scientists wanted to make their probes carry more than one mode of signaling, the probes had to be enlarged even more.
A team of MIT researchers, led by assistant professor of materials and science and engineering Polina Anikeeva and material sciences professor Yoel Fink, may have found a way around this--they’ve invented super-small fiber probes that can signal electrically, chemically, and mechanically in live neural tissue. The multimodal character of the fiber probes enable optical stimulation, neural recording, and drug delivery to the cells of the brain or spinal cord.
The MIT researchers implement an approach borrowed from optical fiber production to craft these thin, almost nanoscale probes: they start with a “preform,” a larger version of the future probe, to make it easier to work with. To this preform they add optical waveguides (to direct light), catheters (for drug delivery), and electrodes (to convey electrical energy); the preforms are then heated and stretched. The process produces many extremely thin, highly flexible fibers while preserving their original component arrangements. This thermal drawing process is comparatively inexpensive and capable of producing thousands of probes at once.
The neural probes created by the MIT team are approximately the width of a human hair (via Nature)
The MIT team tested their neural probes in mice and found that, unlike previous brain-machine interfaces, little damage was caused by the tiny probes, and the communication established between them and their cellular neighbors remained stable for over two months. While the probes were in place, the researchers could communicate with light-sensitive neurons via the probes’ optic channels; they also successfully delivered drugs to the mice via probes. Furthermore, the responses of the surrounding cells could be easily monitored using embedded electrodes.
The fiber probes, they claim, can be implemented for more precise manipulation of neural circuits as well as for easier analysis of its effects on the brain than previously seen. The multimodal nature of the probes also opens up possibilities for the treatment of neurological disorders that cannot be treated with unimodal implants. Additionally, we can customize these probes to suit their purpose by combining different components and channels. “You can have a really broad palette of devices,” says Anikeeva.
There’s still a long way to go before these implants can be used in humans, but their continuing evolution promises some cool things for the future of neurological medicine.
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