Biodegradable implant provides electrical stimulation that speeds up nerve regeneration

Researchers at Northwestern University and the Washington University School of Medicine have come up with the first example of bioelectronic medicine: an implantable and biodegradable wireless device that speeds up nerve regeneration and improves the healing of a damaged nerve.

Collaborators – Northwestern materials scientists and engineers and neurosurgeons at the University of Washington – have developed a device that provides regular electrical impulses to damaged peripheral nerves in rats after a surgical repair process, accelerating regrowth nerves in the legs and improving muscle strength and control. The size of a penny and the thickness of a sheet of paper, the wireless device works for about two weeks before it naturally absorbs into the body.

Scientists believe that such transient technologies could someday supplement or replace pharmaceutical treatments for various medical conditions in humans. This type of technology, which researchers call a "bioelectronic drug," provides therapy and treatment over a clinically relevant time period and directly to the site where it is needed, reducing the side effects or risks associated with permanent implants. classics.

"These engineering systems provide active therapeutic function in a programmable dosage format, and then naturally disappear into the body without leaving a trace," said John A. Rogers of the Northwest, a pioneer in bio-integrated technologies. and co-principal author of the study. "This therapeutic approach allows us to think about options that go beyond drugs and chemistry."

Rogers holds the Louis Simpson and Kimberly Querrey Chair in Materials Science and Engineering, Biomedical Engineering and Neurological Surgery at the McCormick School of Engineering and Feinberg School of Medicine at Northwestern University.

The research will be published on October 8 in the journal Medicine of nature.

Although the device has not been tested in humans, the results of this study are promising as a future therapeutic option for patients with nerve damage. For cases requiring surgery, the usual practice is to administer electrical stimulation during the operation to facilitate recovery. But until now, doctors did not have the means to continuously provide this extra stimulation at different points in the recovery and healing process.

"We know that electrical stimulation during the operation is helpful, but once the operation is complete, the intervention window is closed," said co-lead author Dr. Wilson "Zack Ray, Associate Professor of Neurosurgery, Biomedical Engineering and Orthopedics. surgery at the University of Washington. "With this device we have shown that programmed electrical stimulation can further improve nerve recovery."

Over the last eight years, Rogers and his lab have developed a comprehensive collection of electronic materials, device designs and biodegradable device manufacturing techniques, with a wide range of options offering the opportunity to meet unmet medical needs. When Ray and his colleagues at the University of Washington identified the need for electrical stimulation-based therapies to accelerate wound healing, Rogers and his Northwestern colleagues went to their toolbox and got to work.

They designed and developed a thin and flexible device that wraps an injured nerve and delivers electrical impulses at specific times for days before the device degrades harmlessly into the body. The device is powered and controlled wirelessly by a transmitter located on the outside of the body, which looks a lot like a mobile phone charging mat. Rogers and his team worked closely with the University of Washington team throughout the animal development and validation process.

Researchers at the University of Washington then studied the bioelectronic device in rats with injured sciatic nerves. This nerve sends signals up and down the legs and controls the hamstrings and muscles of the lower legs and feet. They used the device to provide rats with one hour of electrical stimulation for one, three, or six days, or even no electrical stimulation, and then monitored their recovery for the next ten weeks.

They discovered that any electrical stimulation was better than ever to help rats regain muscle mass and strength. In addition, the longer the rats received days of electrical stimulation, the faster and more quickly they recovered nerve signals and muscle strength. No adverse biological effects of the device and its reabsorption have been found.

"Before conducting this study, we were not sure that a longer stimulation would make a difference, and now that we know it, we can start trying to find the ideal amount of time to maximize recovery." "said Ray. "If we had administered electrical stimulation for 12 days instead of six, would there have been more therapeutic benefits? Maybe. We are now looking at that."

By changing the composition and thickness of the materials of the device, Rogers and his colleagues can control the precise number of days during which it remains functional before being absorbed by the body. New versions can provide electrical impulses for weeks before degrading. The ability of the device to degrade in the body replaces a second surgical procedure to remove a non-biodegradable device, thereby eliminating an additional risk to the patient.

"We are making sure the devices disappear," said Rogers. "This concept of transient electronic devices has been a concern for my group for almost 10 years – a great quest for materials science, in a sense, we are excited because we now have the parts, the materials, the devices, the manufacturing approaches, technical concepts at the system level – to harness these concepts to meet the great challenges of human health. "

The research study also showed that the device could function as a temporary pacemaker and as an interface with the spinal cord and other body stimulation sites. These results suggest a broad utility, beyond the peripheral nervous system.

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More information:
Jahyun Koo et al, The bioresorbable wireless electronic system allows sustained non-pharmacological neuroregenerative therapy, Medicine of nature (2018). DOI: 10.1038 / s41591-018-0196-2