A new type of brain implant could give scientists a more precise way to study the brain and could eventually contribute to treatments for neurological conditions such as epilepsy.
Researchers at DTU, the University of Copenhagen, University College London and other institutions have developed a long, needle-thin brain electrode equipped with microscopic channels. Known as the microfluidic Axialtrode (mAxialtrode), the device is designed to provide multiple functional points along the implant. This allows researchers to record neural activity and deliver drugs to specific locations in different parts of the brain.
The findings were published in the journal. Advanced science.
A multifunction tool for brain research
For now, the technology is primarily intended as a research tool. Scientists could use it to investigate how signals travel through different layers of the brain during processes related to epilepsy, memory and decision-making.
In the long term, researchers say mAxialtrode could also have therapeutic applications. One possibility would be to use the device to deliver medications to precise locations while also applying electrical stimulation or light stimulation to selected areas of the brain.
Postdoc Kunyang Sui, who developed the mAxialtrode concept together with Associate Professor Christos Markos, says that one of the main advantages is that several capabilities can be combined in a single implant. That could allow researchers to perform more precise experiments while reducing the need to insert multiple devices into the brain.
“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 particularly angled tip that makes it smaller and reduces the damage caused when placed in the brain,” says Kunyang Sui.
Sui cautions that the technology is still far from routine clinical use. Extensive testing, additional development and regulatory approvals would be needed before it could be used to treat patients.
Beyond conventional optical fibers
Currently, brain researchers use flat-ended optical fibers in many experiments. These fine fibers, made of glass or plastic, can transport light to deep regions of the brain. They are frequently used in optogenetics, a technique in which specific nerve cells are activated by light.
Conventional fibers, however, have an important limitation. They typically interact with brain tissue only at the end of the fiber, meaning researchers can stimulate or monitor only one location at a time.
The outermost end is called the distal tip or “nose” of the fiber. Only at this point is light emitted and contact with the brain tissue occurs. As a result, scientists may be limited to measuring or stimulating one layer of the brain at a time, although many brain functions depend on communication between multiple layers and deeper structures.
How the new brain implant works
The needle-thin mAxialtrode starts out as a much larger polymer rod. The researchers heat the material and transform it into an extremely thin fiber, something like producing a very fine strand of sugar, but with much greater precision.
A light-conducting core runs through the center of the fiber. Around it are eight microscopic channels that can transport liquids. Those channels may also contain extremely thin metal wires that are used to measure electrical activity in the brain.
The finished fiber measures less than half a millimeter wide. It is also very flexible, allowing it to move along with the brain tissue rather than rigidly pressing on it. This difference in stiffness could be important because harder implants can trigger inflammatory responses when they remain in the brain for long periods.
Tested on live mice
The researchers tested the system not only in the laboratory but also “in vivo”, that is, in living mice. The electrode was implanted in the animals’ brains and connected to light sources, recording equipment and small pumps used to deliver fluids.
Experiments showed that the device could stimulate nerve cells using blue and red light. At the same time, the researchers were able to record electrical activity from superficial and deep brain regions, including the cerebral cortex and hippocampus.
They were also able to inject different substances at different depths, with administration points almost three millimeters apart. All of these measurements and forms of stimulation were carried out using a single lightweight fiber, which the mice were able to carry without any obvious signs of discomfort.
Potential applications in epilepsy and neuroscience
The in vivo experiments and neurophysiological validation were performed in close collaboration with Associate Professor Rune W. Berg from the University of Copenhagen and Associate Professor Rob C. Wykes from University College London. His contributions included expertise in the analysis of neural circuits and models relevant to epilepsy.
The research team is now working to patent the technology behind the brain electrode. Scientists are also exploring what it would take to begin testing the device on patients in a clinical setting.