Engineers at MIT were inspired by the sticky substance attached to the rock by barnacles and designed a powerful biocompatible glue that can seal injured tissue and stop bleeding. This new paste can adhere to the surface even if it is covered by blood stains, and can form a tight seal in about 15 seconds. Researchers say this glue can provide a more effective way to treat trauma and help control bleeding during surgery. "We are solving the problem of adhesion in a challenging environment, that is, a humid, dynamic environment of human tissues. At the same time, we are trying to transform this basic knowledge into actual products that can save lives," Xuanhe Zhao, a professor of mechanical engineering, civil and environmental engineering at the Massachusetts Institute of Technology (MIT) and one of the senior authors of the study, said. Christoph Nabzdyk is a cardiac anesthesiologist and critical care physician at the Mayo Clinic in Rochester, Minnesota, and the senior author of this paper published in the journal Nature Biomedical Engineering. Yuk Hyunwoo, a research scientist at MIT, and Jingjing Wu, a postdoctoral fellow, are the main authors of this study. Zhao said that finding a way to stop bleeding is a long-standing problem, but it has not yet been fully resolved. Sutures are usually used to close wounds, but stitching in place is a time-consuming process, which is usually impossible for emergency personnel in emergency situations. Among military personnel, blood loss is the leading cause of death after traumatic injuries, and among ordinary people, blood loss is the second leading cause of death after traumatic injuries. In recent years, some materials that can stop bleeding, also known as hemostatic agents, have been sold on the market. Many of these are made up of patches containing clotting factors, which help the blood to clot on its own. However, it takes a few minutes to form a seal and does not always work on heavily bleeding wounds. Zhao's laboratory has been working on solving this problem for many years. In 2019, his team developed a double-sided tissue tape and demonstrated that it can be used to close surgical incisions. This tape is inspired by the sticky material used by spiders to catch prey in humid conditions. It contains charged polysaccharides that can absorb water from the surface almost instantaneously, removing small dry areas where glue can attach. For the new tissue glue, the researchers once again drew inspiration from nature. This time, they focused on the barnacle. Barnacles are small crustaceans that can attach to rocks, ship hulls, and even other animals such as whales. These surfaces are wet and often dirty, which make adhesion difficult. "This has attracted our attention," Yuk said. "This is very interesting because to seal the bleeding tissue, you have to fight not only with dampness, but also with the contamination of the outflow blood. We found that this creature living in the marine environment is doing exactly the same thing we do when we deal with complex bleeding problems." Researchers' analysis of barnacle gum shows that it has a unique composition. The sticky protein molecules that help the barnacle attach to the surface are suspended in an oil that repels water and any contaminants on the surface, so that the sticky protein is firmly attached to the surface. The MIT research team decided to simulate this glue by modifying an adhesive they had previously developed. This viscous material consists of a polymer called polyacrylic acid and an organic compound called NHS ester. NHS ester provides viscosity, while chitosan is a sugar that can enhance the strength of the material. Researchers freeze thin flakes of this material, grind them into particles, and then suspend these particles in medical silicone oil. When the resulting paste is applied to a wet surface (e.g., tissue covered with blood), the oil repels possible blood and other substances, cross-links the adhered particles, and forms a tight seal on the wound. The researchers' experiments in mice showed that within 15 to 30 seconds after applying the glue, the glue would solidify and bleeding would stop by gentle pressure. The researchers said that compared with the double-sided tape designed by the researchers in 2019, one advantage of this new material is that the paste-like material can be molded into a shape suitable for irregular wounds, and the tape may be more suitable for sealing surgical incisions. Or connect medical equipment to the organization. "The moldable paste can flow in, fit any irregular shape and seal it," Wu said. "This allows users to freely adjust it to fit various irregularly shaped bleeding wounds." In a trial in pigs, Nabzdyk and colleagues at the Mayo Clinic found that the glue quickly stopped liver bleeding and was faster and more effective than the hemostatic agents on the market they compared. It works even when pigs are injected with a strong blood thinner (heparin) so that blood does not spontaneously form clots. Their research has shown that this seal can remain intact for several weeks, giving the underlying tissues enough time to heal itself, and that the inflammation caused by this glue is very small, similar to the inflammation caused by currently used hemostatic agents. After a few months, this glue will be slowly absorbed in the body. If the surgeon needs to enter the wound for repair after the initial application, it can also be removed in advance by applying a solution that dissolves it. The researchers now plan to test the glue on larger wounds, and they hope to prove that the glue is useful for treating traumatic injuries. They also envisioned that this technique might be useful during surgical procedures, because surgeons usually spend a lot of time controlling bleeding. Nabzdyk said: "We are technically capable of performing many complex operations, but we have not really progressed so fast in terms of the ability to quickly control particularly severe bleeding." Another possible application is to help patients who have plastic tubes inserted into blood vessels to stop bleeding, such as those used for arterial or central venous catheters or extracorporeal membrane oxygenation (ECMO). During ECMO, a machine is used to pump the patient's blood out of the body for oxygen. It is used to treat patients with severe heart and lung failure. The catheter is usually inserted for several weeks or months, and bleeding at the insertion site may cause infection.

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