The Suture of the Future
Unless you’re in the garden pest control industry, it might seem bizarre to build your career around slugs. Yet biology professor Andy Smith has done just that. While some see the slug as a gross invertebrate with a trail of goo behind it, he sees a creature with fascinating and unique adaptations that could lead to major improvements in the medical field, specifically surgical glues.
Despite the revolutionary potential of Smith’s work, it’s difficult not to refer to him as “the slug guy.” His work certainly makes for interesting conversation at cocktail parties, he jokes. “It took a while to be completely comfortable with the fact that everyone's first response is, 'Well, that's weird!'” he says. “But usually it doesn't take long to convince people that, yeah, it's weird, but it's interesting, and it's unusual. What made me [interested in being] a biologist from the beginning was that I like really interesting adaptations.”
The particular adaptation he’s researching is how a common slug—specifically the dusky slug or Arion subfuscus— is able to turn the slippery slime by which it traverses the ground into a glue so powerful it can stick a grown man’s fingers together, and he’ll have difficulty prying them apart. And it won’t wash off easily either, despite the fact that the goo is composed mostly of water.
That glue could lead to a replacement for stitches and would be a major improvement over current medical glues, which can fail quickly in warm, moist applications inside the body.
“Gel like this would make an ideal medical adhesive,” Smith says. “It would stick to wet surfaces, and no matter how much the tissue flexed and bent, the gel would flex and bend with it. There would be no leakage or scarring.”
Over the last decade, Smith and his students have been slowly unlocking the biochemistry behind this amazing secretion. Just as important, he has been serving as a mentor to those undergraduates who assist in his lab.
Prior to arriving at Ithaca College in 2000, Smith discovered that a key difference between slime and glue in other mollusks—limpets and marsh periwinkles, specifically—hinged on the addition of a single protein in the mixture. But his first week in Ithaca sent him on a new trajectory when his attention was drawn to some slugs in his backyard.
"So I just picked one up because I'm a biologist, and I looked at it. And all of a sudden it started secreting this ooze all over my fingers, and they started sticking together,” he says. The gel could not be easily removed with paper towels or washing with soap. “And that was an ‘ah-ha’ moment,” he says. “I thought, ‘This material's incredible!’”
Next, he did research to see whether anyone had studied the substance, and he found no one had. The material is “a dilute, tangled network of polymers” that is neither fluid nor solid. Since his first backyard encounter with the dusky slug, Smith and the students assisting in his lab also determined that ions of metal such as zinc, calcium, iron, and copper help the gel stiffen by forming powerful links between the polymers.
This year Smith plans to sequence the amino acids of the proteins in the slug glue to determine their exact structure with a method called high-throughput sequencing.
"It’s a modern technique that's unbelievably powerful,” Smith says. “We could sequence my genome, your genome, anyone's genome in an afternoon." Beyond that, though, he believes he has a good understanding of the biochemistry behind the glue—all the ingredients, as it were— but he still needs to understand how the ingredients are assembled.
That doesn’t mean he hasn’t tried. There’s been some success manually manipulating the slippery slime and causing it to stiffen a bit. But, as Smith notes, "[making it] a little stiffer is not what the slug's doing. The slug is doing something completely dramatic and amazing."
A SCIENTIFIC MENTOR
Sarah Rabice ’14 has spent several semesters in Smith’s lab. "He's sort of become my unofficial academic advisor,” she says. She notes that he encourages students to become more independent as thinkers and objective scientists.
The research methods Rabice has learned under Smith’s tutelage have solidified her interest in pursuing a medical degree, she says, and helped her realize the similarities between how a scientist and doctor problem solve.
"I feel like researching has helped me push the limits of my own creativity and innovation,” she says. “Understanding how much more there is to know about that topic has definitely been inspiring to me in pursuing education in general."
Smith prizes the opportunity to help facilitate this personal growth. "You can tell when the student first comes into the lab, and we have a lab meeting—they don't know what to do. And the seniors who are in the lab are bouncing ideas off each other, and critiquing my ideas, and telling me why my ideas don't work, or coming up with better ideas,” he says.
“To see the difference is really amazing,” he says. “You see how independent they become, how creative, how good at coming up with really logical, interesting ideas. It's very rewarding to see that." And while the students eventually move on, Smith keeps chipping away at the secrets of the Arion subfuscus glue that bound his fingers together all those years ago. He foresees a day when sealing a wound with stitches or staples is relegated to the past.
“Stitches are a very crude way to put someone back together again,” he observes.
It’s a surgical method that stretches back millennia, after all. But biological gels are an understudied natural substance in general, Smith says. Not all slugs produce glues with the same properties as the dusky slug, and plenty of other animals ooze secretions that have potential applications for humans.
"All of these animals can produce designer gels for all kinds of different purposes,” he says. "They can control mechanics of these gels in all kinds of interesting ways. Long term, I envision scientists figuring out different ways of making gels that could be useful, [just as these] animals do.”