Thin, flexible, self-powered, and bioresorbable implant dissolves within the body once the bone is knitted back together
In 2017, Green Bay Packers quarterback Aaron Rodgers broke his right collarbone in a game against the Minnesota Vikings. Typically, it takes about 12 weeks for a collarbone to fully heal, but by mid-December fans and commentators were hoping the three-time MVP might recover early and save a losing season. So did Xudong Wang, a professor of materials science and engineering at the University of Wisconsin–Madison and an expert in creating thin, movement-powered medical devices.
Researchers know that electricity can help speed up bone healing, but “zapping” fractures has never really caught on, since it requires surgically implanting and removing electrodes powered by an external source. A major update of that same electrostimulation concept, Wang’s latest invention which may help many others by making electrostimulation a much more convenient option to speed up bone healing. His thin, flexible device is self-powered, implantable and bioresorbable, so once the bone is knitted back together, the device’s components dissolve within the body. The device is described the new device in the journal Proceedings of the National Academy of Sciences. While there are external stimulators that create an electric field to accelerate healing indirectly, the ideal solution is stimulating the bone directly. Putting the device inside the body, however, has unique requirements — not the least of which is powering it, according to Wang.
To create the new fracture electrostimulation device, or FED, Wang and his team started with a triboelectric nanogenerator, a thin-film device with microstructured surfaces that converts mechanical energy produced by tiny movements into electric power. They coupled the nanogenerator with a pair of electrodes to distribute the electric field to the bone. They built these ultrathin, biodegradable and bioresorbable components on a substrate of poly(lactic-co-glycolic acid), a commonly used FDA-approved biocompatible polymer. The researchers’ initial tests confirmed that small movements of the device did indeed create an electrical stimulation of about 4 volts, which it could sustain for over six weeks. They then tested the device on rats. The animals implanted with the device completely recovered from a tibia fracture in about six weeks, much more quickly than animals in a control group. The mineral density and flexural strength of the healed bones also reached the same level as healthy bones in the animals that received the electrostimulation. After the treatment, the devices degraded and absorbed into the rats’ bodies with no complications and no need for surgical removal.
Source: UW-Madison news release