Up to now, injured areas have usually been sewn up during operations on the intestine. As an alternative, researchers have now developed a surgical adhesive tape that is supposed to seal injuries securely and dissolves by itself after a few weeks. The plaster is designed to flexibly adapt to bowel movements and, compared to a suture, reduce the risk of the injury tearing open again. The researchers have successfully tested their patch on rats and pigs. In future studies, they want to further develop it for use in humans.
If the large intestine is damaged – for example due to injuries or surgical interventions – it has to be stitched up so that the tissue can grow back together. However, the suture places an uneven load on the edges of the wound, which often causes scar tissue to form. There is also a risk that the injury will reopen. The resulting leaks can increase patient mortality by more than 30 percent.
Gluing instead of sewing
A team led by Jingjing Wu from the Massachusetts Institute of Technology (MIT) in Cambridge has now developed a possible alternative: a surgical tape that can be used to easily close wounds in the intestine without suturing. “The patch consists of a non-stick top layer and a dry, bioadhesive back layer, resulting in a thin, flexible, transparent and ready-to-use patch with tissue-like mechanical properties,” the researchers describe. During the operation, the patch should be easy to stick to the injury. Within a few seconds, the adhesive bonds to the tissue and holds the wound edges together evenly.
In experiments with rats, the patch biodegraded after about twelve weeks without any toxic components being detected in the blood. “We think this surgical tape is a good basic technology to actually make a ready-to-use product out of it,” says Wu’s colleague Hyunwoo Yuk. “Surgeons could use it the way they use duct tape in the non-surgical world. It requires no preparation or previous steps. You just take it out, open it and use it.”
Plaster with tissue properties
The top of the patch consists of a smooth layer of biodegradable plastic that is stretchy and strong similar to natural intestinal tissue. “We don’t want the plaster to be weaker than the fabric, because otherwise it could burst,” says Yuk. “We also don’t want it to be stiffer, because that would restrict the peristaltic movement in the gut, which is essential for digestion.” The researchers used polyacrylic acid, an absorbent material also used in diapers, as the base material for the adhesive side. When it comes into contact with moisture, it absorbs water and becomes sticky. To increase adhesion to the tissue, Wu and his colleagues added so-called NHS esters, which can bind to proteins in the tissue.
An added hydrogel ensures that the tape holds its shape and is stable in the body for at least a month – long enough for a typical intestinal injury to heal. The first tests revealed the problem that the hydrogel swelled up too much when it came into contact with moisture, thereby stretching the crack that it was supposed to seal. “But we used a simple trick,” says Yuk. “We pre-stretched the adhesive layer a bit and then introduced the non-adhesive layer. When in contact with moist tissue, the pre-stretching now compensates for the swelling.”
Planned use in humans
Using a cell culture with human cells, the researchers showed that the patch is biocompatible and does not impair cell growth. In the next step, they tested it on live rats and pigs that they had inflicted with intestinal injuries that they treated with the patch. Compared to conventional sutures, the patch caused fewer inflammatory reactions in the test animals and scarring was also minimal. After four weeks, the injuries were fully healed with no sign of the dreaded leakage.
In further studies, the researchers want to further develop the patch and ultimately test it on humans. “Every year, millions of operations are performed worldwide to repair gastrointestinal defects, and the leakage rate is as high as 20 percent in high-risk patients,” says Wu’s colleague Xuanhe Zhao. “The tape could solve this problem and potentially save thousands of lives.”
Source: Jingjing Wu (Massachusetts Institute of Technology, Cambridge) et al., Science Translational Medicine, doi: 10.1126/scitranslmed.abh2857