Biodegradable implant encourages nerve regeneration

October 10, 2018

In a recent study conducted on rats, a wireless, biodegradable implant proved to be more effective than conventional surgery.

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, the implant stimulated and 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,” said Dr. John A. Rogers, a researcher in bio-integrated technologies at Northwestern.

“This approach to therapy allows one to think about options that go beyond drugs and chemistry.”

The device could also fuction 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. Unlike neurons, peripheral nerves can regenerate after injury.

Car accidents, sports injuries and repetitive tasks involving fingers, including typing, often 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 may require surgery to stimulate the nerves, especially if there may be total loss of feeling to the area where the nerve is damaged.

“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.”

Rogers and his team spent eight years developing a complete collection of electronic materials, device designs and manufacturing techniques for biodegradable devices with a broad range of options, while Ray and his colleagues identified the need for electrical stimulation-based therapies to accelerate wound healing.

The Northwestern and Washington University teams collaborated to create 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 electrical stimulation for an hour a day over a span of 10 weeks.

The electrical stimulation was effective at recovering muscle mass and muscle strength, 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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