David Mooney, Harvard University, Wyss Institute
Tough Adhesive for Diverse Wet Surface
Written by Hortense Le Ferrand
Cyanoacrylate, or “Super Glue,” is one of the best adhesive commercially available today. But not only Super Glue is not entirely biocompatible and doesn’t match the mechanics of soft tissues, it also has very low performance under wet conditions.
David Mooney and his team have looked into Nature to find inspiration: some slugs, when threatened, secrete an adhesive and tough mucus. This mucus has the form of a hybrid hydrogel consisting in an ionically-crosslinked polysaccharide network and a covalently-crosslinked network. In comparison, synthetic hydrogels are brittle and slippery.
One of his former post-docs, Jianyu Li—now assistant professor at McGill University, used chitosan, a long molecular chain polysaccharide, to penetrate and bind to the negatively charged surfaces of cells and tissues, as the ionically-crosslinked part, and a covalently chitosan synthesized using carbodiimide chemistry for the other part. Performing peeling tests, the adhesion energy measured greatly exceeded the values of Super Glue.
Exploring another system of alginate and polyacrylamide, he showed that bloody pig skins could be glued together with a value of 1000 Jm-2, almost 10 times higher than obtained with Super Glue under wet conditions, and this after only 3 minutes adhesion.
Thanks to the biocompatibility of the chemicals used, this adhesive has potential applications as external wound dressing, sealant for tissue repair, hemostatic agent to stop bleeding and even soft actuator around tissues.