Caddisfly larvae spun into surgical tape

SALT LAKE CITY – Often used as fishermen's bait, sticky caddisfly larvae may soon be used to suture wounds, according to researchers at the University of Utah.
The small, moth-like insect spins silk, much like butterflies and spiders, albeit underwater instead of on dry land. The chemical and structural properties of the larvae make it a probable and valuable adhesive tape during surgery because it could be used to hold together skin from the inside.
"I picture it as sort of a wet Band-Aid, maybe used internally in surgery – like using a piece of tape to close an incision, as opposed to sutures," said Russell Stewart, an associate professor of bioengineering at the U. and principal author of a new study of the properties of the fly's silk. The study will be published this week in Biomacromolecules, a journal of the American Chemical Society. He said gluing things together underwater isn't easy.
"Have you ever tried to put a Band-Aid on in the shower? This insect has been doing this for 150 million to 200 million years," he saidStewart studies natural adhesives at the U., including another he discovered made by sandcastle worms on the shore between high tide and low tide ocean waves. That type of natural "glue" has the potential to help repair small broken bones in humans by holding them together. He learned of the potential of the caddisfly larva from a Smithsonian Institution scientist who showed him several of the tube-shaped larval cases that caddisflies spin underwater. It was then that he put on his boots and waded through the Provo River, looking for larvae.
After growing them in his lab, researchers analyzed the silk fibers, finding that they stitched together glass beads from inside their shelters.
"It's like using Scotch tape on the inside of a box to hold it together," Stewart said. "It's really like a tape more than anything else – a tape that works underwater." Next up, they plan to study how strong the silk, or spun larva, can be and whether it can be reproduced synthetically and then used as a surgical adhesive.
In addition to caddisflies, the sandcastle worms, as well as mussels and sea cucumbers, are among the four categories of living organisms that have the ability to make adhesives under water.
And just as it took researchers a while to figure it out, the system of spinning something sticky enough to hold onto its eggs in the aquatic environment evolved independently for the flies, too, helping the creatures live and thrive, Stewart said.