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Medical glue inspired by sticky slug mucus

The Dusky Arion slug, shown here, adds certain proteins to its mucus to make a glue. H. Krisp, [CC BY 3.0 (http://creativecommons.org/licenses/by/3.0)], via Wikimedia Commons

The slug known as Dusky Arion (Arion subfuscus) coats itself with mucus to keep moist. It can add certain proteins to its mucus to make a glue. With this glue, the slug can attach so strongly to a surface that it can’t be carried off by a predator.

Inspired by the Dusky Arion, a research team led by Dr. David J. Mooney at Harvard University created a family of medical glues that could be sticky, strong, stretchy, and nontoxic. The study was supported in part by NIH’s National Institute of Dental and Craniofacial Research (NIDCR). Results were published on July 28, 2017, in Science.

The research team designed a glue that has two layers. One layer is a sticky surface that contains a polymer. Like the proteins in the slug’s glue, the polymers create strong chemical bonds to the underlying tissue. The other layer is a stretchable, strong hydrogel, such as alginate-polyacrylamide. The team made a family of such two-layer glues by combining different polymers.

The researchers tested the strength of these glues in many scenarios. The new glues adhered strongly to the surfaces of tissues from a pig, including skin, cartilage, heart, and liver. The team found that the adhesion could be as strong as natural cartilage binding to bone. The glues adhered so well because they are stretchy rather than brittle like currently available medical adhesives, such as cyanoacrylate. This flexibility allows them to spread out the forces that normally cause adhesives to fail.

A new, flexible adhesive material can stick to biological tissues even when wet, and can be formed into sheets (teal blue) and custom shapes (dark blue). Wyss Institute at Harvard University

The team compared the performance of their family of glues to commercially available medical adhesives. The new glues adhered much more strongly than commercial adhesives. They also adhered more slowly, so that a surgeon would be able to position a seal precisely over tissues before the glue hardened.

Surgeons need adhesives that stick to wet surfaces. To test whether the new glues might be suitable for surgery, the researchers covered pig skin with blood to approximate a real-life surgery. Even in this wet environment, the new glues were sticky. The commercial adhesive didn’t work as well with blood.

Surgeons also require adhesives that will adapt to moving tissues, such as a beating heart. When tested with a heart, the team’s glues were stickier than the commercial adhesive. Even when the heart expanded, the seal remained stuck. The researchers also used the glues to seal a hole in the wall of a rat liver.

In lab tests, the new family of glues wasn’t toxic to a culture of human cells. When implanted under the skin or on the heart of lab rats, the glues caused less or about the same immune reactions as two commercial adhesives.

“The key feature of our material is the combination of a very strong adhesive force and the ability to transfer and dissipate stress, which have historically not been integrated into a single adhesive,” Mooney says. The new family of adhesive materials has the potential to be developed into a variety of medical products, such as an adhesive to glue medical devices to tissues, a stretchy patch to apply to tissue, or an injectable solution to repair deep injuries.

—by Geri Piazza