Starting with fibers taken from pig tissue, researchers at the Massachusetts Institute of Technology (MIT) have developed dissolving sutures that can be loaded with molecular sensors or medication. The hope is that the new sutures could speed healing and/or send up the red flag when something is wrong at a surgical site.
According to the surgeon Galen of Pergamon, in ancient Greece, when gladiators had their tendons severed, medics used sutures made from silk and the twined intestines of sheep or horses to patch them back up. The animal-based fibers became known as catgut, even though they had nothing to do with the innards of felines. A version of catgut sutures is still used to this day in some surgeries, especially in cases where the stitches can't easily be removed, as catgut naturally dissolves in about 90 days.
Looking to expand the utility of catgut, researchers at MIT took pig tissue and used a detergent-based process to wash it free of cells, leaving behind a fiber made mostly from collagen and other biomolecules. They then coated the fiber, which they named "De-gut," in a hydrogel and experimented with embedding different particles in the gel to help with wound healing and sensing.
"What we have is a suture that is bioderived and modified with a hydrogel coating capable of being a reservoir for sensors for inflammation, or for drugs such as monoclonal antibodies to treat inflammation," said Giovanni Traverso, the senior author of the study. "Remarkably, the coating also has the capacity to retain cells that are viable for a prolonged period." Traverso is an associate professor of mechanical engineering at MIT and a gastroenterologist at Brigham and Women’s Hospital.
For the sensing research, Traverso and his team put peptide-coated microparticles in the hydrogel. The peptides were released when enzymes related to inflammation were present. Once released, the peptides can be detected in urine, so a simple urinalysis could find them and alert doctors to troublesome inflammation at a suture site inside the body.
For drug delivery, the researchers successfully embedded substances used in the treatment of inflammatory bowel disease in the hydrogel. Both monoclonal antibodies and steroids were packaged into polymers that are used to control the release rate of drugs, and then carried in the hydrogel on the suture surface. The researchers say that other drugs could be embedded as well, including antibiotics or chemotherapy drugs.
Finally, the researchers experimented with using the sutures to deliver stem cells that were engineered to express fluorescent markers. By tracking the glowing cells, the team found that they remained viable on the suture surface inside mice for at least seven days. The stem cells were also able to produce a substance known as vascular endothelial growth factor (VEGF), which stimulates the production of new blood cells that could help speed healing at surgical sites.
The study authors were initially inspired to find sutures that could work well for Crohn's disease patients – who in severe cases need to have portions of their intestinal tract removed – but they say the sutures could work well for a variety of surgeries, an avenue of investigation they hope to explore.
Their work has been published in the journal, Matter.
Source: MIT