Researchers have developed a new type of neural implant that can restore limb function to amputees and others who have lost the use of their arms or legs. In a study on rats, researchers from the University of Cambridge used a device to improve communication between the brain and paralyzed limbs. The device combines flexible electronics and human stem cells (the “reprogrammed” mother cells of the body) to better integrate with the nerves and motor function of the limbs.
Previous attempts to use neural implants to restore limb function have often been unsuccessful because over time, scar tissue forms around the electrodes, preventing communication between the device and the nerve. By placing a reprogrammed layer of muscle cells from stem cells between the electrodes and living tissue, the researchers found that the device integrated with the host’s body and prevented scar tissue formation. Cells survived on the electrode throughout the 28-day experiment; this is the first time it has been observed in such a long time.
By combining two cutting-edge treatments for nerve regeneration (cell therapy and bioelectronics) in a single device, the researchers say they can improve functionality and sensitivity, overcoming the shortcomings of both approaches. While extensive research and testing will be needed before use in humans, the device is a promising development for amputees or those who have lost a limb or limbs. The results were reported in the journal March 22, 2023. Science Advances.
A major problem when trying to repair injuries that result in a limb or loss of limb function is the inability of neurons to regenerate and repair damaged neural circuits.
“For example, if a person has an arm or leg amputated, all the signals from their nervous system are still there, even if the physical limb is gone,” said Dr Damiano Barone, of the Cambridge Department of Clinical Neurology, who led the study. “The challenge of integrating prostheses or restoring function of an arm or leg is to take the information from the nerve and transfer it to the limb to restore function.”
One of the ways to solve this problem is to insert a nerve into the large muscles of the shoulder and attach electrodes to it. The problem with this approach is that scar tissue forms around the electrode and only surface level information can be obtained from the electrode.
In order to achieve better resolution, any implant would need much more information from the electrodes to restore its function. To increase sensitivity, the researchers wanted to create something that could work at the scale of a single nerve fiber or axon.
“There’s a small voltage in the axon itself,” Barone said. “But when it’s connected to the muscle cell, which has a much higher voltage, it’s easier to remove the signal from the muscle cell. This is where the sensitivity of the implant can be increased.”
Researchers have developed a biocompatible, flexible electronic device thin enough to be attached to the end of a nerve. A stem cell layer reprogrammed into muscle cells was then placed on the electrode. This type of stem cell, called induced pluripotent stem cell, was used in this way for the first time in a living organism.
“These cells give us a tremendous degree of control,” said Barone. “We can tell them how to behave and control them throughout the experiment. By placing the cells between the electronics and the living body, the body doesn’t see the electrodes, it only sees the cells so that scar tissue does not form.”
The Cambridge biohybrid device was implanted in the paralyzed forearm of mice. The stem cells, which had grown into muscle cells before implantation, integrated into the mouse’s forearm nerves. While the rats’ forearms did not reactivate, the device was able to pick up signals from the brain that controlled movement. When attached to a remaining nerve or a prosthetic limb, the device can help restore motion.
The cell layer also improved the performance of the device, increasing resolution and allowing long-term monitoring inside a living organism. Cells survive 28-day experiment: This is the first time cells have been shown to survive in such an extended experiment.
The researchers say their approach has several advantages over other attempts to restore function in amputees. In addition to easy integration and long-term stability, the device is small enough to require only keyhole surgery for implantation. While other neural interface technologies for restoring function in amputees require complex individual interpretation of cortical activity associated with muscle movements, the device developed by Cambridge is a highly scalable solution as it uses “ready-made” cells.
In addition to its potential to restore function to people who have lost the use of a limb or limbs, the researchers say their device could also be used to control prosthetic limbs by interacting with certain axons responsible for motor control.
“This interface has the potential to revolutionize the way we interact with technology,” said co-author Amy Rochford of the Engineering Department. “By combining living human cells with bioelectronic materials, we have created a system that can communicate with the brain in a more natural and intuitive way, opening up new possibilities for prosthetics, brain-machine interfaces and even cognitive development.”
Also from the Department of Engineering, co-author Dr. “This technology represents an exciting new approach to neural implants that we hope will open up new treatments for patients who need it,” said Alejandro Carnicer-Lombarte.
“This was a very risky task and I’m very happy it worked out,” said Professor George Malliaras of the Cambridge School of Engineering, who led the research. “It’s one of those things where you don’t know if it’ll take two years or ten years before it works, and it’s been very effective in the end.”
Researchers are currently working to further optimize the devices and improve their scalability. The team applied for a patent for the technology, with support from Cambridge Enterprise, the university’s technology transfer arm.
Source: Port Altele
