Monday, April 14, 2014

Surgical Glue Inspired by the Sandcastle Worm and Slugs

Los Angeles Times:
Inspired by creepy crawly creatures like the slug and the sandcastle worm, a team of scientists has created a surgical adhesive that could safely seal up the hearts of babies born with congenital heart defects.

The bioinspired glue, described in Science Translational Medicine, could replace damaging staples, weak or toxic glues and reduce the need for repeated surgeries, said study coauthor Jeffrey Karp, a bioengineer at Brigham and Women’s Hospital in Boston.

When such young patients need closure devices implanted, they come with complications, Karp said.

“These devices, they don’t grow with the patient -- and these children have to come back multiple times to have devices removed and re-implanted,” Karp said. “It’s highly invasive and has a lot of complications associated with it."

Sutures take time -- “It’s difficult to tie knots in small spaces,” Karp said -- and staples damage tissue, as they have to be bent to stay in. The glues that are used are often hydrogels that are weak in the body’s watery environment. The stronger kind, a sort of “medical-grade crazy glue,” is very toxic, Karp said.

"There are about 30,000 heart operations performed per year on children with congenital defects in the U.S.," study coauthor Dr. Pedro del Nido, chief of cardiac surgery at Boston Children's Hospital, said in an email.

So having a safe, strong, nontoxic, minimally invasive glue could potentially help a lot of kids. That’s in part why Del Nido teamed up with Karp, who has made a practice of finding surgical solutions in the natural world.

Karp and his colleagues began thinking about how animals navigate watery environments. Many of the medical glues are largely hydrophilic – that is, their components prefer to dissolve in water. But the secretions that animals use to stick to things (or to stick other things together) often contain agents that are hydrophobic – that repel water. They’re also very thick and viscous, so when they attach to a surface, they don’t flow. They stay put.

These two factors seem to be common practice with a number of gunk-generating animals, including the sandcastle worm, which glues bits of sand together to make its shelter along California shorelines; and slugs, whose slime helps them climb walls even in wet weather.

The glue the researchers came up with using those two principles is thick like honey. Unlike other surgical glues, which chemically bond with a tissue surface, this glue makes a mechanical connection – infiltrating spaces between the collagen fibers in the tissue and locking in. (It’s a little like another bioinspired solution Karp recently came up with – a skin graft device based on the tenacious grip of the parasitic spiny headed worm.)

“We’re kind of surrounded by solutions,” Karp said. “I truly believe that evolution is the best problem-solver.”

This glue can be cured using ultraviolet light in five seconds flat – very handy if you’re operating on a living heart in flowing blood.

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