Glue Seals Bleeding Organs in Seconds

Inspired by the sticky substance that barnacles use to cling to rocks, MIT engineers have designed a strong, biocompatible glue that can seal injured tissues and stop bleeding. 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 say.

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,” says Xuanhe Zhao, a professor of mechanical engineering and civil and environmental engineering at MIT and one of the senior authors of the study. Finding ways to stop bleeding is a longstanding problem that has not been adequately solved, Zhao says. Sutures are commonly used to seal wounds, but putting stitches in place is a time-consuming process that usually isn’t possible for first responders to perform during an emergency situation. Among members of the military, blood loss is the leading cause of death following a traumatic injury, and among the general population, it is the second leading cause of death following a traumatic injury.

In recent years, some materials that can halt bleeding, also called hemostatic agents, have become commercially available. Many of these consist of patches that contain clotting factors, which help blood to clot on its own. However, these require several minutes to form a seal and don’t always work on wounds that are bleeding profusely. Zhao’s lab has been working to address this problem for several years

For their new tissue glue, the researchers once again drew inspiration from the natural world. This time, they focused their attention on the barnacle, a small crustacean that attaches itself to rocks, ship hulls, and even other animals such as whales. These surfaces are wet and often dirty — conditions that make adhesion difficult. “This caught our eye,” Yuk says. “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. We found that this creature living in a marine environment is doing exactly the same thing that we have to do to deal with complicated bleeding issues.” The researchers’ 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 decided to try to mimic this glue by adapting an adhesive they had previously developed. This sticky material consists of a polymer called poly(acrylic acid) embedded with an organic compound called an 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.

Christoph Nabzdyk, a cardiac anesthesiologist and critical care physician at the Mayo Clinic in Rochester, Minnesota, is also a senior author of the paper, which appears today in Nature Biomedical Engineering. MIT Research Scientist Hyunwoo Yuk and postdoc Jingjing Wu are the lead authors of the study.

Source: https://news.mit.edu/

Micromotors Deliver Oral Vaccines

Researchers are working on new generations of oral vaccines for infectious diseases. But to be effective, oral vaccines must survive digestion and reach immune cells within the intestinal wall. As a step in this direction, UC San Diego nanoengineering researchers have developed oral vaccines powered by micromotors that target the mucus layer of the intestine.

The work appears in the ACS journal Nano Letters. It’s a collaboration between the labs of nanoengineering professors Joseph Wang and Liangfang Zhang at the UC San Diego Jacobs School of Engineering.

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The lack of needles is one reason oral vaccines are attractive. Another reason: oral vaccines can generate a broad immune response by stimulating immune cells within the mucus layer of the intestine to produce a special class of antibody called immunoglobulin A (IgA). The NanoLetters paper documents the team’s efforts to use magnesium particles as tiny motors to deliver an oral vaccine against the bacterial pathogen Staphylococcus aureus. When coated over most of their surfaces with titanium dioxide, magnesium microparticles use water as fuel to generate hydrogen bubbles that power their propulsion.

To develop the oral vaccine, the researchers coated magnesium micromotors with red blood cell membranes that displayed the Staphylococcal α-toxin, along with a layer of chitosan to help them stick to the intestinal mucus. Then, they added an enteric coating that protects drugs from the acidic conditions of the stomach.

The micromotors safely passed through the stomach to the intestine, at which point the enteric coating dissolved, activating the motors. Imaging of mice that had been given the vaccine showed that the micromotors accumulated in the intestinal wall much better than non-motorized particles. The micromotors also stimulated the production of about ten times more IgA antibodies against the Staphylococcal α-toxin than the static particles.

Source: http://jacobsschool.ucsd.edu/