European researchers have created a slender brain probe that can record signals, administer drugs, and activate several brain areas simultaneously. Known as the microfluidic Axialtrode, or mAxialtrode, the tool is a pliable fiber containing eight narrow channels running down its length. In living mice, it detected electrical activity from the cerebral cortex and hippocampus, delivered materials to distinct depths, and sent light into nerve cells, all during one procedure.
This research hails from DTU, the University of Copenhagen, University College London, and other institutions. Its findings appeared in the journal Advanced Science. Rather than the rigid silicon common to most brain implants today, the device uses soft, plastic-like optical fibers, which the scientists claim lessen irritation and inflammation within the brain. It also sports an angled tip that trims its size, cutting harm when it is inserted into the organ.
“Most current brain implants are based on hard materials such as silicon, which can irritate the brain and trigger inflammatory reactions in the tissue. The new implant differs in that it is made of soft, plastic-like optical fibers and has a specially angled tip that makes it smaller and reduces the damage caused when it is placed in the brain.”
Recording, Delivery, and Stimulation in One Fiber
The mAxialtrode does three things at once:
| Function | Details |
|---|---|
| Recording | A light-conducting core runs through the fiber’s center, surrounded by eight microscopic channels holding thin metal wires for measuring electrical activity. Tested in living mice, it recorded signals from the cerebral cortex and hippocampus. |
| Delivery | The same channels that carry wires also transport liquids; researchers injected different substances at separate depths, with delivery points spaced almost three millimeters apart. |
| Stimulation | The fiber carries light into deep regions of the brain; in the mouse tests, it stimulated nerve cells using both blue and red light. |
The three functions run at once through a single thin fiber that the mice carried without showing any sign of discomfort. Researchers say this method gives scientists a more accurate, less invasive means of studying the brain, and that the technology might eventually aid in treating neurological disorders like epilepsy.
The Limitation of Conventional Fibers
Many brain studies rely on flat-ended optical fibers, slender rods of glass or plastic that transmit light into the depths of the brain. These fibers serve as a key tool in optogenetics, where particular nerve cells are switched on by light.
Conventional fibers carry a notable drawback. They generally engage with brain tissue solely at the fiber’s far end, which confines researchers to stimulating or monitoring a single spot at any given moment. That far end is known as the distal tip, or the “nose”, of the fiber. It is here that light emerges and where the fiber makes contact with brain tissue. Because of this arrangement, investigators may find themselves restricted to gauging or exciting one brain layer at a time, despite the fact that numerous brain functions hinge on interaction between several layers and deeper regions.
Rather than gathering data solely from the tip of the device, the mAxialtrode places its functional points along its length. This arrangement lets scientists capture, transmit, and activate signals from several brain areas simultaneously.
How the Fiber Is Made
Researchers start with a large polymer rod and heat it to pull it into an extremely thin fiber, much as a very fine strand of sugar is produced, though with far greater precision. The result is the needle-thin mAxialtrode, which measures less than half a millimeter across.
This particular device is built to bend and shift alongside brain tissue instead of forcing its way through it with fixed rigidity. That difference in how stiff the device is matters greatly, since implants that are much harder can set off inflammatory reactions after sitting inside the brain for extended time. The soft material paired with the specially shaped tip is designed to cut down on harm during the moment the implant is put into the brain.
Who Built the Implant
Kunyang Sui, a postdoc, and Associate Professor Christos Markos built the mAxialtrode together. The research group is currently working on getting a patent for the technology that powers the brain electrode. They are also looking into what steps would be needed to start testing the device in patients through a clinical trial.
The in vivo experiments and the neurophysiological validation were carried out in close cooperation with Associate Professor Rune W. Berg of the University of Copenhagen and Associate Professor Rob C. Wykes from University College London. Their contributions covered expertise in analyzing neural circuits and models relevant to epilepsy.
What the Tests Showed
The experimenters placed their device inside the heads of living mice, where it sat linked to light sources, recording gear, and small pumps for delivering fluids.
Researchers were able to stimulate nerve cells with both blue and red light during the experiments. They recorded electrical activity from shallow and deeper brain regions, including the cerebral cortex and hippocampus, at the same time. They also injected different substances at separate depths, with delivery points spaced nearly three millimeters apart.
The animals underwent all the tests and received every kind of stimulus through one slender fiber, which they bore without showing any outward sign of distress.
The Path to Clinical Use
Before the technology can be used to treat patients, extensive testing, further development, and regulatory approvals will all be needed, according to Sui. The researchers are working on securing patents for the technology and considering what would be required to begin testing the device in patients within a clinical setting. No timeline for those plans has been given in the source.
The design of the device, with its flexible material, aims to cut down on the kind of brain swelling that often results from implants made of harder substances left inside the head over time. Still, the scientists stress that this technology has not reached a point where it could be put to use in human patients.
Comparing the mAxialtrode to Other Implants
Instead of putting its functional points only at the tip, the mAxialtrode’s design arranges them along the length of the implant. This arrangement lets researchers record, deliver, and stimulate across several brain regions simultaneously, a capability the source calls a key strength of the device.
Researchers are using the device as a means to study the brain with greater accuracy, and it might someday help with therapies for conditions like epilepsy. At present, though, it stands as a promising early step rather than a finished product.
Source material: “Scientists create a needle-thin brain implant that can do three jobs at once,” ScienceDaily.
Get the Notebook.
The day's best stories and every fresh verdict, in plain English, in your inbox by seven. One email a day, no more.