Biodegradable implant provides electrical stimulation that speeds nerve regeneration

October 8, 2018, Northwestern University
The wireless device naturally absorbs into the body after a week or two. Credit: Northwestern University

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

The collaborators—materials scientists and engineers at Northwestern and neurosurgeons at Washington University—developed a device that delivers regular pulses of electricity to damaged peripheral nerves in rats after a surgical repair process, accelerating the regrowth of nerves in their legs and enhancing the ultimate recovery of muscle strength and control. The size of a dime and the thickness of a sheet of paper, the wireless device operates for about two weeks before naturally absorbing into the body.

The scientists envision that such transient engineered technologies one day could complement or replace pharmaceutical treatments for a variety of medical conditions in humans. This type of technology, which the researchers refer to as a "bioelectronic medicine," provides therapy and treatment over a clinically relevant period of time and directly at the site where it's needed, thereby reducing side effects or risks associated with conventional, permanent implants.

"These engineered systems provide active, therapeutic function in a programmable, dosed format and then naturally disappear into the body, without a trace," said Northwestern's John A. Rogers, a pioneer in bio-integrated technologies and a co-senior author of the study. "This approach to therapy allows one to think about options that go beyond drugs and chemistry."

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

The research will be published Oct. 8 in the journal Nature Medicine.

While the device has not been tested in humans, the findings offer promise as a future therapeutic option for nerve injury patients. For cases requiring surgery, standard practice is to administer some electrical stimulation during the surgery to aid recovery. But until now, doctors have lacked a means to continuously provide that added boost at various time points throughout the recovery and healing process.

"We know that electrical stimulation during surgery helps, but once the surgery is over, the window for intervening is closed," said co-senior author Dr. Wilson "Zack" Ray, an associate professor of neurosurgery, of biomedical engineering and of orthopedic surgery at Washington University. "With this device, we've shown that electrical stimulation given on a scheduled basis can further enhance nerve recovery."

Over the past eight years, Rogers and his lab have developed a complete collection of electronic materials, device designs and manufacturing techniques for biodegradable devices with a broad range of options that offer the potential to address unmet medical needs. When Ray and his colleagues at Washington University identified the need for electrical stimulation-based therapies to accelerate wound healing, Rogers and colleagues at Northwestern went to their toolbox and set to work.

They designed and developed a thin, flexible device that wraps around an injured nerve and delivers electrical pulses at selected time points for days before the device harmlessly degrades in the body. The device is powered and controlled wirelessly by a transmitter outside the body that acts much like a cellphone-charging mat. Rogers and his team worked closely with the Washington University team throughout the development process and animal validation.

The Washington University researchers 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 one hour per day of electrical stimulation to the rats for one, three or six days or no electrical stimulation at all, and then monitored their recovery for the next 10 weeks.

They found that any electrical stimulation was better than none at all at helping the rats recover muscle mass and muscle strength. In addition, the more days of electrical stimulation the rats received, the more quickly and thoroughly they recovered nerve signaling and muscle strength. No adverse biological effects from the device and its reabsorption were found.

"Before we did this study, we weren't sure that longer stimulation would make a difference, and now that we know it does, we can start trying to find the ideal time frame to maximize recovery," Ray said. "Had we delivered electrical stimulation for 12 days instead of six, would there have been more therapeutic benefit? Maybe. We're looking into that now."

By varying the composition and thickness of the materials in the device, Rogers and colleagues can control the precise number of days it remains functional before being absorbed into the body. New versions can provide electrical pulses for weeks before degrading. The ability of the device to degrade in the body takes the place of a second surgery to remove a non-biodegradable device, thereby eliminating additional risk to the patient.

"We engineer the devices to disappear," Rogers said. "This notion of transient electronic devices has been a topic of deep interest in my group for nearly 10 years—a grand quest in materials science, in a sense. We are excited because we now have the pieces—the materials, the devices, the fabrication approaches, the system-level engineering concepts—to exploit these concepts in ways that could have relevance to grand challenges in human health."

The research study also showed the device can work as a temporary pacemaker and as an interface to the spinal cord and other stimulation sites across the body. These findings suggest broad utility, beyond just the peripheral nervous system.

Explore further: Electrical nerve stimulation can reverse spinal cord injury nerve damage in patients

More information: Jahyun Koo et al, Wireless bioresorbable electronic system enables sustained nonpharmacological neuroregenerative therapy, Nature Medicine (2018). DOI: 10.1038/s41591-018-0196-2

Related Stories

Electrical nerve stimulation can reverse spinal cord injury nerve damage in patients

July 2, 2015
Approximately 12,000 spinal cord injuries (SCI) happen every year in the U.S., the majority caused by car accidents, falls, sporting accidents and gunshot wounds. Better emergency care and therapy have made SCI manageable, ...

Electrical stimulation improves paralyzed patients' function

September 15, 2017
Nearly 282,000 people in the U.S. live with paralysis following a spinal cord injury (SCI). A review of more than 90 studies found that electrical stimulation may help restore function in those paralyzed after SCI. The article ...

Electrical nerve stimulation could help patients regain motor functions sooner

May 2, 2018
Researchers at The Ohio State University Wexner Medical Center are among the first in the world studying how a specific type of neurostimulator can improve rehabilitation for stroke patients.

Race to nerve regeneration: faster is better

October 3, 2011
A team of researchers led by Clifford Woolf and Chi Ma, at Children's Hospital Boston and Harvard Medical School, Boston, has identified a way to accelerate the regeneration of injured peripheral nerves in mice such that ...

Direct electrical current used to preferentially inhibit pain-transmitting neurons

April 18, 2018
Using computer models and laboratory rats, Johns Hopkins researchers have demonstrated that "direct electrical current" can be delivered to nerves preferentially, blocking pain signals while leaving other sensations undisturbed.

Precise nerve stimulation via electrode implants offers new hope for paralysis patients

November 22, 2016
Patients with spinal cord injuries might one day regain use of paralyzed arms and legs thanks to research that demonstrates how limbs can be controlled via a tiny array of implanted electrodes.

Recommended for you

Research shows signalling mechanism in the brain shapes social aggression

October 19, 2018
Duke-NUS researchers have discovered that a growth factor protein, called brain-derived neurotrophic factor (BDNF), and its receptor, tropomyosin receptor kinase B (TrkB) affects social dominance in mice. The research has ...

Good spatial memory? You're likely to be good at identifying smells too

October 19, 2018
People who have better spatial memory are also better at identifying odors, according to a study published this week in Nature Communications. The study builds on a recent theory that the main reason that a sense of smell ...

How clutch molecules enable neuron migration

October 19, 2018
The brain can discriminate over 1 trillion odors. Once entering the nose, odor-related molecules activate olfactory neurons. Neuron signals first accumulate at the olfactory bulb before being passed on to activate the appropriate ...

Scientists discover the region of the brain that registers excitement over a preferred food option

October 19, 2018
At holiday buffets and potlucks, people make quick calculations about which dishes to try and how much to take of each. Johns Hopkins University neuroscientists have found a brain region that appears to be strongly connected ...

Gene plays critical role in noise-induced deafness

October 19, 2018
In experiments using mice, a team of UC San Francisco researchers has discovered a gene that plays an essential role in noise-induced deafness. Remarkably, by administering an experimental chemical—identified in a separate ...

Brain cells called astrocytes have unexpected role in brain 'plasticity'

October 18, 2018
When we're born, our brains have a great deal of flexibility. Having this flexibility to grow and change gives the immature brain the ability to adapt to new experiences and organize its interconnecting web of neural circuits. ...

2 comments

Adjust slider to filter visible comments by rank

Display comments: newest first

choirgal
not rated yet Oct 08, 2018
Has research been done (or is in progress) to repair or regenerate the auditory nerve? I ask because I lost hearing in one ear due to a viral infection which damaged that auditory nerve.

I would appreciate any information about progress in auditory nerve regeneration. Thank you
pntaylor
not rated yet Oct 09, 2018

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.