One of the Holy Grail inventions of medical devices is one that is bio-compatible, serves a therapeutic function, and can be reabsorbed into the human system when its work is finished. Researchers at Northwestern University and Washington University School of Medicine in St. Louis have developed what they said is the first example of this future for medicine with an implantable, biodegradable wireless device. This device speeds nerve regeneration to improve the healing of a damaged nerve.
Regrowth of Nerves With Electrical Stimulation
Materials scientists and engineers at Northwestern and neurosurgeons at Washington University put their heads together to develop the device, which can deliver regular pulses of electricity to damaged peripheral nerves in rats after a surgical repair process. The team showed in tests that this accelerates the regrowth of nerves in the rats' legs, enhancing the ultimate recovery of muscle strength and control, according to a Northwestern University news release.
“These engineered systems provide active, therapeutic function in a programmable, dosed format and then naturally disappear into the body, without a trace,” said John A. Rogers, professor of materials science and engineering, biomedical engineering, and neurological surgery at Northwestern, and a pioneer in bio-integrated technologies. “This approach to therapy allows one to think about options that go beyond drugs and chemistry.”
The bioresorbable electronic medical device developed by the team is tiny—just the size of a dime and the thickness of a sheet of paper—and can operate wirelessly for about two weeks before naturally absorbing into the body, researchers said.
|A bioresorbable device developed by researchers to provide stimulation to nerves to promote healing is showed on a model of a human nerve. Researchers at Northwestern University and Washington University School of Medicine in St. Louis invented the device. (Image source: Northwestern University and Washington University School of Medicine)|
Scientists envision that such devices can not just complement, but even replace pharmaceutical treatments or implants for various medical conditions. The key is that they provide treatment for an allotted period of time directly at a site where such treatment is needed. This type of treatment can reduce side effects or risks associated with medications or other types of medical implants, including surgeries to implant and replace devices, researchers said.
Specifically, the device wraps around an injured nerve and delivers electrical pulses at selected time points for days before dissolving. A transmitter outside the body powers and controls the device remotely.
The team so far has tested the device only in rats with injured sciatic nerves, using it to send signals up and down the legs and control the hamstrings and muscles of the lower legs and feet. The device provided one hour per day of electrical stimulation to the rats for one, three, or six days—or no electrical stimulation at all—while researchers monitored the rats’ recovery for the next 10 weeks.
No Adverse Effects
What the team discovered is that any electrical stimulation was better than none at helping the rats recover muscle mass and muscle strength in the damaged areas, said Dr. Wilson Ray, an associate professor of neurosurgery, biomedical engineering, and orthopedic surgery at Washington University. In addition, the more days of electrical stimulation the rats received, the more quickly and thoroughly they recovered nerve signaling and muscle strength, he said. Moreover, researchers found no adverse biological effects from the device and its reabsorption.
“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.”
The team controlled the precise number of days the device remained functional inside the body by varying the composition and thickness of the materials in the device, Rogers said. Some of the newer versions of the device they developed can provide electrical pulses for weeks before degrading—which takes the place of a surgery to remove the device, he said.