Injured tendons are notoriously tricky to repair. Researchers at Harvard’s Wyss Institute have now developed a two-faced biomaterial that can improve healing, with one side that firmly sticks to tendons, while a low-friction outer surface keeps it gliding against other tissues. Better yet, they can be loaded with slow-release drugs to reduce scarring and inflammation.
Tendon injuries are fairly common, both from playing sports and from general aging. They can be painful and impair a patient’s ability to move their limbs, and worse still take a long time to heal. Even after they do, tendons often don’t return to their full former mechanical strength after severe injuries, resulting in reduced mobility.
So for the new study, the Wyss researchers set out to develop a new material that could help repair tendons more effectively. They started with a surgical adhesive gel the team created a few years ago that was inspired by the strongly sticky mucus of the Dusky Arion slug. The researchers then adapted this platform, which they call Tough Gel Adhesives, to make a version for patching up tendons.
The new hydrogel has two very different surfaces, and as such has been named Janus Tough Adhesives (JTAs), after a Roman God with two faces. The first surface contains chitosan, which firmly bonds to tendons to keep two sides of a tear together to improve healing. The other surface does the opposite, using the plain hydrogel to help the tendon glide against other tissues during movement.
The team tested them in a series of experiments using animal and human tissue. On isolated pig tendons still covered in blood, the JTAs bonded more strongly than other tissue adhesives. The researchers also implanted the material into patellar, foot flexor and Achilles tendons of live rats, and found that they bonded strongly and non-invasively. Similar results were seen in tests using human cadavers.
In further tests, the team encapsulated corticosteroid drugs into the hydrogel, which should help reduce inflammation during healing and the formation of scars afterwards. Tests in rats with injuries to their knee tendons showed that inflammation passed much more quickly.
“Importantly, when we applied JTAs to ruptured patellar tendons of rats, they remained in place over their three-week implantation and facilitated tendon healing,” says Benjamin Freedman, first author of the study. “They also reduced the formation of scars by 25 percent, compared to surgically repaired tendons that we didn’t treat with JTAs.”
While human tests have yet to be conducted, the team says that all the components of the JTAs are already known to be biocompatible, which is an important first step.
The research was published in the journal Nature Biomedical Engineering. The team describes the work in the video below.
Source: Wyss Institute