Andrew Smith, a biologist at Ithaca College, was plucking the invasive Dusky Arion slugs out of his garden one day when one excreted slime on him.
His fingers were stuck together as if he had grabbed a glob of crazy glue. But amazingly, the slug glue didn’t stick on the slug itself.
That inspired him and his students to conduct a series of studies on different aspects of the gloop in order to figure out if the sticky slime from those pesky slugs actually had some use. Could it be the key to a new type of medical adhesive?
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For the Dusky Arion slug, the sticky slime is actually a defense mechanism. When they’re under threat, the critters will excrete a glue-like substance out of its back.
If a bird or other animal then attempts to eat the slug it’ll get a mouthful of glop that essentially clamps its mouth shut.
“If you take a quarter and stick it to the ceiling with the glue, you’d need to attach about 10 pounds for the glue to fail and the quarter to fall,” Christopher Gallego-Lazo, an undergraduate student that conducted one of the studies on the slug, said.
But it’s not just its stickiness that makes it unique. “Current glues are not very elastic,” Rebecca Falconer, another undergraduate student in Smith’s lab, said.
This is a problem with medical glues or any type of glue that has to be used on the body. “They’re strong but they’re not deformable. They can’t bend and move with your skin or heart or stomach. And they’re not adhesive in wet environments. If you have a Bandaid on your arm you can feel it tugging because it doesn't move with your skin.”
The slug glue has all of these properties—but exactly why that is remains a bit elusive.
Research so far has revealed some interesting information about its makeup. For example, the slime’s molecules are held together by special chemical bonds called sacrificial bonds, which means they exist to come apart. When the glue is tugged or pulled those bonds break before its other, permanent bonds, leaving the glue intact.
Gallego-Lazo’s research showed the sacrificial bonds present in the slug glue are actually self-healing.
“After you put force on the glue and let it sit for a day or two it will actually self repair,” he told The Daily Beast, adding that the glue can regain up to 60%of its initial strength. In his research to discover what gives the glue its strength he suspected it was the metals present inside but so far has been unable to target which ones, specifically, make the glue so strong.
Falconer has been looking closely at earlier research that found the glue has a group of 11 proteins that are unique to the slug. Her work is in isolating the genetic makeup of those proteins and synthesizing them individually in the lab (because they’re so sticky they’re too difficult to take apart and study one by one).
“We’re testing their function to see if they have any ability to stiffen gels [while maintaining flexibility],” she says. “In doing this we’ve so far found three that proved they can stiffen gels by themselves. We put the glue on a machine that smashes it between two plates and then wiggles it called a rheometer. It measures how hard it is to break the bonds within the glue so when we add these proteins it’s a lot harder to break the glue apart.”
Falconer and Gallego-Lazo, both set to graduate this year, will pass their work off to other students. They say that despite these findings there’s still a lot to be done to figure out how all the elements of the glue work together to make it so unique: analyzing the remaining 9 proteins, studying the slime’s different metals, looking at its carbohydrates.
But in several years, once researchers at the lab have cracked the code, there could be a whole new type of glue finding its way into patients and surgeries around the world.
