Biodegradable device speeds nerve regeneration in rats

The implantable wireless device is designed to stimulate damaged nerves in rats, suggesting it could be used for therapy in people with leg injuries.

By Allen Cone
Biodegradable device speeds nerve regeneration in rats
This is a model of a thin, flexible device (silver and circular) that wraps around an injured nerve and delivers electrical pulses. The researchers found the device -- about the size of a dime -- was effective in rats. Photo courtesy of Northwestern University

Oct. 8 (UPI) -- An implantable, biodegradable wireless device that stimulates damaged nerves in legs was more effective than conventional surgery, according to research with rats.

Researchers at Northwestern University and Washington University School of Medicine developed a device the size of a quarter and thickness of a sheet of paper that delivers regular pulses of electricity to damaged peripheral nerves.


According to the findings, published Monday in the journal Nature Medicine, the device regrew nerves in rats' legs and enhanced the ultimate recovery of muscle strength and control. It operated for about two weeks before the body naturally absorbed it.

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


They said the device also can work as a temporary pacemaker, as well an interface to the spinal cord and other stimulation sites.

Bioelectronic medicine provides therapy and treatment directly at the site where it's needed, reducing side effects or risks associated with conventional, permanent implants.

Damage to peripheral nerves, which link the brain, spinal cord and rest of body, is called peripheral neuropathy. The peripheral nerves can regenerate after injury, unlike neurons in the brain and spinal cord.

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Car accidents, sports injuries and repetitive tasks involving fingers, including typing, leave people with numbness, tingling and weakness in their hands, arms or legs.

Painkillers and physical therapy are used in minor cases. But severe cases -- in which there may be total loss of feeling to the area where the nerve is damaged -- may require surgery to stimulate the nerves,

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

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At Northwestern, Rogers and his lab spent eight years developing a complete collection of electronic materials, device designs and manufacturing techniques for biodegradable devices with a broad range of options.


Ray and his colleagues at Washington University also identified the need for electrical stimulation-based therapies to accelerate wound healing.

With the Washington University researchers, the Northwestern team made a thin, flexible device that wraps around an injured nerve and delivers electrical pulses.

A transmitter outside the body charges and powers the device much like a cellphone-charging mat.

In rats with sciatic nerves, the Washington University researchers tested the device by sending signals up and down the legs, which controls the hamstrings and muscles of the lower legs and feet.

Over six days, the devices provided one hour per day of electrical stimulation, or none at all, monitoring recovery for 10 weeks.

The electrical stimulation was more effective at recovering muscle mass and muscle strength than nothing at all, and the more days of electrical stimulation the rats received, the better the results.

"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."


They also varied the composition and thickness of the materials in the device.

"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.

"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."

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