Researchers at MIT have developed a method that could be used to ensure long-lasting medical device implants do not trigger an immune response. The aim of their research is to allow implants to keep working without being rejected by the body.
They pointed to a specific use case: artificial pancreas implants that periodically release insulin under the skin to help treat diabetes without daily injections or inserted tubes. But so far product developers have been blocked by the body’s immune system, which would grow a defensive layer of scar tissue around the device, effectively sealing it off and restricting the doses of insulin.
To overcome this foreign-body response, MIT researchers built a soft, robotically powered device that can inflate and deflate. Every 12 hours the implant can quickly expand and contract to shake off the build-up of immune cells.
In early experiments using mice, the researchers found the shape-shifting implant could work for much longer than a typical drug delivery device.
“We’re using this type of motion to extend the lifetime and the efficacy of these implanted reservoirs that can deliver drugs like insulin, and we think this platform can be extended beyond this application,” Associate Professor Ellen Roche, of MIT’s Institute for Medical Engineering and Science, said to MIT News.
Previously, implant makers have used immunosuppressant drugs or device coatings to fight off scar tissue, which can cause a device to fail within weeks or months. The foreign body response can also affect breast implants, heart valves and pacemakers.
The ultimate goal of the MIT researchers, with their collaborators at the National University of Ireland at Galway, is to develop a largely drug-free implant that could potentially harbor insulin-secreting pancreatic islet cells.
“The idea would be that the cells would be resident in the reservoir and they would act as an insulin factory,” said Roche. “They would detect the levels of glucose in blood and then release insulin according to what was necessary.”
The research team built a soft, patch-shaped, polyurethane implant containing two chambers: one houses an insulin reservoir, while the other can be pressurized to bulge out its sides. Slipped under the skin, it connects to an external controller that can make the device inflate and deflate once per second for five minutes at a time, twice per day.
In the mouse study, researchers saw it took longer for scar tissue to form around the device, and when it did, its collagen fibers aligned themselves in specific ways that allowed insulin doses to slip through and escape into the body.
Their work was published this month in the journal Nature Communications, with funding from Science Foundation Ireland, the Juvenile Diabetes Research Foundation and the National Institutes of Health.
Future applications could include implants that deliver immunotherapies to treat cancer or drugs to help stave off heart failure.
“You can imagine that we can apply this technology to anything that is hindered by a foreign body response or fibrous capsule and have a long-term effect,” said Roche. “I think any sort of implantable drug delivery device could benefit.”