Electricity helps the heart beat, the muscles twitch, and the body communicate with the brain. Now scientists are increasingly using electricity to promote healing. Unlike previous inventions that were often quite bulky, new “electroceutical” devices are easier to wear, and some can even biodegrade inside the body. Here are a few designs that could someday aid patients in recovery.
On Your Nerves: This implant stimulates peripheral nerves for up to two weeks before it breaks down and is absorbed by the body. Photo: Northwestern University
Research has found that electric fields can accelerate the repair of damaged nerves, likely by triggering the release of nerve-regenerating chemicals by neurons and nearby cells. However, such therapy is currently applied only during surgery, says materials scientist John Rogers at Northwestern University, in Evanston, Ill.
Now Rogers and his colleagues have developed a biodegradable implant that can continuously deliver electrical pulses to nerves, and breaks down when it is no longer needed. The device is roughly as wide as a small coin and as thick as a sheet of paper, and is flexible enough to wrap around an injured nerve. It’s powered and controlled wirelessly by a transmitter outside the body, and can electrically stimulate a nerve for about two weeks before the body absorbs it.
In experiments with rats that have injured sciatic nerves, which control the hamstrings and muscles of the lower legs and feet, the devices provided 1 hour of electrical stimulation per day for one, three, or six days. When the scientists monitored the rats for 10 weeks, they found that the more stimulation the rats received, the more quickly and thoroughly the rodents recovered nerve signaling and muscle strength. The researchers noticed no negative side effects from the device or its absorption.
The scientists now plan to test their implants on larger animals as the next step toward someday testing on humans. They also want to see if stimulating an injured nerve for longer periods of time provides even more benefits.
Electroceuticals: Xudong Wang applies an electric bandage that accelerates healing to graduate student Yin Long. Photo: Sam Million-Weaver
The body naturally generates electrical fields during healing. “Once there is a wound, cells will push ions through their membranes to generate an electric field,” which helps the cells align and grow in the direction of the wound, says materials scientist Xudong Wang at the University of Wisconsin–Madison.
Knowing this, Wang and his colleagues developed a bandage that converts mechanical energy emitted by a patient’s body motions into electricity. “We’re looking to apply electric fields to mimic what nature does,” he says.
Specifically, the bandage relies on the phenomenon known as triboelectricity, the most common cause of static electricity. When two substances repeatedly touch and then separate, the surface of one material can steal electrons from the other—which is why rubbing your feet on a carpet builds up electric charge.
The bandage consists of a Teflon strip that slides back and forth over a copper-coated plastic layer. When looped around the torsos of rats, the bandages generated electrical pulses whenever the rodents breathed and reduced the time it took for an incision to heal to just 3 days, compared with up to 12 days for the normal healing process.
Scientists have known for years that electricity could help repair skin, but most electrotherapy devices today administer intense shocks. Wang says that the new bandage’s gentler pulses reduced the production of reactive oxygen species—chemicals that could potentially harm tissue—by nearly a factor of five.
The bandages are made of relatively common materials and are simple to fabricate, suggesting they should not cost much more than a regular bandage, Wang says. The scientists now plan to test their devices on pig skin, which more closely imitates human tissue, he adds.
Flexible Protection: This patch disrupts bacteria that infect wounds. Photo: The Ohio State University Wexner Medical Center
As many as 80 percent of all wound infections involve microbes that have constructed slimy fortresses known as biofilms to shelter the germs from antibiotics and the body’s natural defenders. Electric bandages may be able to fight against biofilm infections, said Chandan Sen, who developed one such bandage when he was director of Ohio State University’s center for regenerative medicine and cell-based therapies. Scientists had previously tried preventing biofilms with drugs, but bacteria quickly evolve to resist those drugs. (In August, Sen became director of a new regenerative medicine center at Indiana University.)
Sen and his colleagues noted that bacteria rely heavily on electrical charges to stick to surfaces and to communicate. “Bacteria have an electrical ecosystem, which, if you perturb, takes away their ability to adhere and to communicate with each other,” Sen says.
Sen’s team developed bandages that have silver and zinc printed onto them, and generate a weak electric field when moistened with bodily fluids such as sweat or blood. In experiments on pigs with burn wounds, the bandages prevented biofilms from forming when applied within 2 hours after the scientists infected the burns with bacteria. The bandages could also disrupt biofilms that had formed when applied seven days after infection, helping the pig’s white blood cells attack the infections.
Vomaris Innovations, in Tempe, Ariz., is now commercializing this technology. Sen, who holds a stake in the company, says this research is also currently in a U.S. Department of Defense–funded clinical trial on burn victims. He and his colleagues are independently investigating whether these bandages can fight multidrug-resistant bacteria. “I think these ‘electroceuticals’ make up a field that can grow in a very big way in the near future,” Sen says.
This article appears in the February 2019 print issue as “Heal Faster With Electricity.”