The new paste can adhere to surfaces even when they are covered with blood, and can form a tight seal within about 15 seconds of application. Such a glue could offer a much more effective way to treat traumatic injuries and to help control bleeding during surgery, the researchers said.
“We are solving an adhesion problem in a challenging environment, which is this wet, dynamic environment of human tissues. At the same time, we are trying to translate this fundamental knowledge into real products that can save lives,” said mechanical engineer Professor Xuanhe Zhao, one of the senior authors of the study.
Finding ways to stop bleeding is a long-standing problem that has not been adequately solved, Zhao said. Sutures are commonly used to seal wounds, but putting stitches in place is a time-consuming process that is not usually possible during an emergency situation. Among members of the military, blood loss is the leading cause of death following traumatic injuries, and it is the second-leading cause among the general population.
Haemostatic agents that can halt bleeding have become commercially available in recent years. Many of these consist of patches that contain clotting factors, which help blood to clot on its own. These require several minutes to form a seal, however, and do not always work on wounds that are bleeding profusely.
Zhao’s lab has been working to address this problem for several years. In 2019, his team developed a double-sided tissue tape and showed that it could be used to close surgical incisions. This tape, inspired by the sticky material that spiders use to capture their prey in wet conditions, included charged polysaccharides that absorb water from a surface almost instantaneously, creating a small, dry patch that the glue can adhere to.
For the new tissue glue, the researchers once again drew inspiration from barnacles, which attach themselves to rocks, ship hulls and even other animals such as whales in wet and dirty conditions – factors that make adhesion difficult.
“This caught our eye,” said MIT research scientist and lead author Hyunwoo Yuk. “It's very interesting, because to seal bleeding tissues you have to fight with not only wetness but also the contamination from this outcoming blood.”
Analysis of barnacle glue revealed that it has a unique composition. The sticky protein molecules that help barnacles attach to surfaces are suspended in an oil that repels water and any contaminants found on the surface, allowing the adhesive proteins to attach firmly to the surface.
The MIT team mimicked the natural glue by adapting an adhesive they had previously developed. This sticky material consists of a polymer called polyacrylic acid embedded with an organic compound called NHS ester, which provides adhesion, and chitosan, a sugar that strengthens the material. The researchers froze sheets of this material, ground it into microparticles, and then suspended those particles in medical-grade silicone oil.
When the resulting paste is applied to a wet surface such as blood-covered tissue, the oil repels the blood and other substances that might be present, allowing the adhesive microparticles to ‘crosslink’ and form a tight seal over the wound.
Tests on wounds in rats showed that the glue sets and bleeding stops within 15-30 seconds of application, with the gentle application of pressure.
One advantage over the double-sided tape is that the paste can be moulded to fit irregular wounds, the researchers said. The tape could be better suited to sealing surgical incisions or attaching medical devices to tissues.
In tests in pigs, cardiac anaesthesiologist and senior author Christoph Nabzdyk and colleagues at the Mayo Clinic in Minnesota found the glue was able to rapidly stop bleeding in the liver. It reportedly worked much faster and more effectively than the commercially available haemostatic agents they compared it to. It even worked when strong blood thinners were given to the pigs, so that the blood did not form clots spontaneously.
The teams’ studies showed that the seal remains intact for several weeks, giving the tissue time to heal, and that the glue induces little inflammation, similar to that produced by haemostatic agents. The glue is slowly ‘resorbed’ within the body over months. It can also be removed earlier by applying a solution that dissolves it, if surgeons need to go in after the initial application to repair the wound.
The researchers now plan to test the glue on larger wounds, which they hope will demonstrate that the glue would be useful to treat traumatic injuries. They also envision that it could be useful during surgical procedures, which often require surgeons to spend a great deal of time controlling bleeding.
Postdoc Jingjing Wu was also a lead author of the study, which was published in Nature Biomedical Engineering.
Want the best engineering stories delivered straight to your inbox? The Professional Engineering newsletter gives you vital updates on the most cutting-edge engineering and exciting new job opportunities. To sign up, click here.
Content published by Professional Engineering does not necessarily represent the views of the Institution of Mechanical Engineers.