Scientists have developed a super strong, flexible adhesive material inspired by the glue secreted by slugs that sticks to biological tissues even when wet without causing toxicity. The “tough adhesive” is biocompatible and binds to tissues with a strength comparable to the bodys own resilient cartilage.
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. Slugs secrete a special kind of mucus when threatened that glue it in place, making it difficult for a predator to pry it off its surface. This glue was previously determined to be composed of a tough matrix peppered with positively charged proteins, which inspired Jianyu Li, an assistant professor at McGill University in Canada and colleagues to create a double- layered hydrogel consisting of an alginate-polyacrylamide matrix supporting an adhesive layer that has positively- charged polymers protruding from its surface. The polymers bond to biological tissues via three mechanisms – electrostatic attraction to negatively charged cell surfaces, covalent bonds between neighbouring atoms, and physical interpenetration – making the adhesive extremely strong.
The teams design for the matrix layer includes calcium ions that are bound to the alginate hydrogel via ionic bonds. When stress is applied to the adhesive, those “sacrificial” ionic bonds break first, allowing the matrix to absorb a large amount of energy before its structure becomes compromised. In experimental tests, more than three times the energy was needed to disrupt the tough adhesives bonding compared with other medical-grade adhesives. When it did break, what failed was the hydrogel itself, not the bond between the adhesive and the tissue, demonstrating an unprecedented level of simultaneous high adhesion strength and matrix toughness. Such a high-performance material has numerous potential applications in the medical field, either as a patch that can be cut to desired sizes and applied to tissue surfaces or as an injectable solution for deeper injuries.