Slug-inspired bio-glue binds like cartilage

(Credit: Wyss Institute at Harvard University)

The research was carried out by members of Harvard’s Wyss Institute for Biologically Inspired Engineering and John A Paulson School of Engineering and Applied Sciences (SEAS). Seeking to improve on current medical adhesives, the team was inspired by the slug, which secretes a special mucus when threatened that helps it stay fixed to its surface.

Previous studies had shown the mucus was formed of a tough matrix interspersed with positively charged proteins. This inspired the Harvard team to create a double-layered hydrogel, consisting of an alginate-polyacrylamide matrix. The matrix then supports an adhesive layer that has positively charged polymers protruding from its surface.

These polymers form a triple bond with biological surfaces: via electrostatic attraction, covalent bonds and physical penetration. According to the team, the hydrogel’s strength and flexibility come from a combination of the polymers and the supporting matrix.

“Most prior material designs have focused only on the interface between the tissue and the adhesive,” said first author Jianyu Li, a former postdoctoral fellow at the Wyss Institute and now an assistant professor at McGill University.

“Our adhesive is able to dissipate energy through its matrix layer, which enables it to deform much more before it breaks.”

The researchers tested the hydrogel on a variety of pig tissues, including skin, heart, artery and liver. They found the adhesive was not only biocompatible but could bind tissues with a strength similar to cartilage, even when they were wet. The gel was used to bond implants in rats for two weeks and to seal a hole in a pig heart that was put through thousands of cycles of stretching.

According to its creators, the bio-glue has potential to be used in medical patches for surface wounds, as well as an injectable solution for deeper injuries. It could also be used to attach medical devices to their target structures, such as an actuator to support heart function.

“We can make these adhesives out of biodegradable materials, so they decompose once they’ve served their purpose,” said study co-author Adam Celiz, who is now a lecturer at Imperial College London’s Department of Bioengineering.

“We could even combine this technology with soft robotics to make sticky robots, or with pharmaceuticals to make a new vehicle for drug delivery.”

The research is published in the journal Science.