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Worm glue may be just what the doctor ordered

An undersea worm has provided researchers with the recipe for a glue that surgeons could use to piece together shattered bones.
Image: Sandcastle worm
A sandcastle worm makes its tubular home. An adhesive inspired by the worm's glue could be used to help live bones repair after surgery. Fred Hayes /
/ Source: Discovery Channel

An undersea worm has provided researchers with the recipe for a glue that surgeons could use to piece together shattered bones.

The sandcastle worm makes its tubular home by sticking bits of sand together. This is a remarkable feat considering the worm's glue works underwater and somehow "dries" after the worm applies it.

"Biology gave us a big new idea," said Russell Stewart of the University of Utah in Salt Lake City, who led the research. "That worm had to solve a whole bunch of very complicated adhesion problems in order to glue things together underwater."

"If you wanted to glue bones together in open surgery, the problems are very similar to the problems that these marine organisms face in order to glue sand grains together," Stewart said, since both environments are wet.

Most bone repair is done with pins, plates and screws. However, when bone fragments are too small, these instruments can be cumbersome.

"There is a real medical need for good adhesives that work well but promote regeneration," said biomedical engineer Jennifer Elisseeff of Johns Hopkins University in Baltimore, who was not involved in the research. "I have doctors asking for it all the time."

"Going to nature is a nice approach," she continued. "Nature has taken a lot of time to evolve and develop these mechanisms."

The secret to the worm's success is combining two highly charged proteins with charged ions. These components bind so tightly to one another that they make a separate fluid within the water, rather than dissolving and floating away.

The worm also has figured out how to get the glue to solidify at the right time underwater. After the proteins are released from the animal's adhesive ducts into the water, some shift in conditions — likely a change in pH — causes the glue to solidify within about 30 seconds.

The researchers have studied how the worm's cement works to design a synthetic version of the protein glue. The current version of the researchers' adhesive is about twice as strong as the sandcastle worm's glue. "We are working to increase the bond strength," Stewart said.

While a pH shift will make the synthetic glue harden, the researchers have found that a temperature change also will cause their glue to set. In fact, one version of the adhesive developed by the team is a liquid at room temperature, but hardens at body temperature — an ideal combination for surgical use.

The ideal surgical cement also will be biodegradable, so it disappears as the bone heals. The team has incorporated a protein into the synthetic adhesive's structure to achieve this goal.

The researchers presented their work at a meeting of the American Chemical Society in Washington, D.C.

Before the glue can be used in the operating room, Stewart said, the team will have to show that it is safe when used in the human body.

"There's a real clinical need for this adhesive, but the clinical potential won't be fully known until we've seen work understanding the biocompatibility," Elisseeff said. "How is this going to act on wet tissues? Can a cell survive nearby this adhesive?"

Such tests will determine whether the glue will sink or swim.