It’s hard to get glue to work underwater – unless you’re a mussel. Scientists have now created a new adhesive that combines the stickiness of mussel’s natural glue with the slimy, germ-repelling nature of mucus.
Trying to stick wet surfaces together is an exercise in futility, as the water molecules form a barrier between the surface and molecules in the adhesive. But mussels seem to have no problem with this, aggressively attaching themselves to rocks and ship hulls.
Scientists have been inspired by mussels to create new adhesives that work in a particularly important wet environment – the human body. The material has been used to make surgical glues that stop bleeding, hold skin grafts together without scarring, bond implants to bones, and keep stem cells in place long enough to repair tissue damage.
Engineers from MIT and Freie Universität Berlin have now found a way to make mussel-inspired adhesives even better with the help of a bodily substance: mucus. This stuff naturally lubricates the inner surfaces of the body and protects them from infection, which could help for many of the biomedical applications of the adhesive.
The combo didn’t come out of nowhere. To strengthen their glue, mussels use two chemical groups, called catechols and thiols, which cross-link like the hooks and loops of Velcro. Thiols are also present in mucus proteins, called mucins, so the team wanted to see if the two could link up.
To investigate, the researchers combined natural mucin proteins and synthetic polymers based on mussel adhesives into solutions of different strengths. And sure enough, it seemed to work well as an adhesive.
“It’s like a two-part epoxy,” said George Degen, lead author of the study. “You combine two liquids together, and chemistry starts to occur so that the liquid solidifies while the substance is simultaneously glueing itself to the surface.”
In a series of tests, the new adhesive was used to stick surfaces together, while the researchers measured how quickly the mixture solidified and how strongly it stuck. So far, it seems to do so about as well as current medical adhesives.
“Depending on how much cross-linking you have, we can control the speed at which the liquids gelate and adhere,” said Rainer Haag, co-author of the study. “We can do this all on wet surfaces, at room temperature, and under very mild conditions. This is what is quite unique.”
In other tests, the researchers spread the adhesive onto glass panels and incubated it with bacteria overnight, to see how well it prevented build-up of the bugs.
“We found if we had a bare glass surface without our coating, the bacteria formed a thick biofilm, whereas with our coating, biofilms were largely prevented,” said Degen.
The researchers plan to continue iterating on the mixture to find the best version for medical applications. It could also be used as an infection-preventing coating for implants.
The research was published in the journal PNAS.
Source: MIT
