Sandcastle worms live in intertidal surf, building sturdy tube-shaped homes from bits of sand and shell and their own natural glue. University of Utah bioengineers have made a synthetic version of this seaworthy superglue, and hope it will be used within several years to repair shattered bones in knees, other joints, and the face.
"You would glue some of the small pieces together," says Russell Stewart, associate professor of bioengineering and senior author of the study published in the journal Macromolecular Biosciences and also presented at the 238th American Chemical Society National Meeting.
"When you break the top of a bone in a joint, those fractures are difficult to repair because if they are not aligned precisely, you end up with arthritis and the joint won't work anyway. So it's very important to get those pieces aligned as well as possible."
In lab tests using cow bone pieces from groceries, the synthetic sea-worm glue - a first-generation prototype - performed 37 percent as well as commercial superglue.
Stewart expects the synthetic worm glue will be tested on animals within a year or 2, and will be tested and used on humans in 5 to 10 years.
The synthetic sandcastle worm glue would not be used to repair large fractures such as major leg and arm bones, for which rods, pins, and screws now are used. But Stewart envisions that it might be used for gluing together small bone fragments in fractured knees, wrists, elbows, ankles, and other joints, and also the face and skull.
"If a doctor rebuilds a joint with pins and screws, generally weight is kept off that joint until it's healed," Stewart says. "So our goal isn't to rebuild a weight-bearing joint with glue. It is to hold the pieces together in proper alignment until they heal. We see gluing the small fragments back into the joint."
In their study, Stewart and colleagues wrote, "It is especially difficult to maintain alignment of small bone fragments by drilling them with screws and wires. An adjunctive adhesive could reduce the number or volume of metal fixators while helping maintain accurate alignment of small bone fragments to improve clinical outcomes."
Bioengineer Patrick Tresco, associate dean for research at the University of Utah's College of Engineering, says, "Most current adhesives do not work when surfaces are wet so they are no good for holding together bone, which is wet and bloody. There is nothing like it [the synthetic worm glue] on the market today."
The synthetic glue also can carry drugs, so it could be used to deliver pain killers, growth factors, antibiotics, anti-inflammatory medicines, or even stem cells to sites where bone fragments are glued, "simultaneously fixing the bone and delivering potent drugs or even genes to the spots where they are needed," Stewart says.
And where pieces of bone now are cut out due to cancer, the adhesive might be used to firmly attach "tissue scaffolds" used to encourage regrowth of the missing bone.
Stewart is seeking to patent the synthetic sea worm glue so it can be licensed to an outside company that would develop it as a product. He hopes to make better versions that have more bonding power, are biocompatible in the human body, and biodegradable.
"Ultimately, we intend to make it so it is replaced by natural bone over time," Stewart says. "We don't want to have the glue permanently in the fracture."
Stewart says some synthetic superglues or "instant glues" are used instead of sutures for superficial skin wounds. But because of toxicity or toxic byproducts, "they are not suitable for deep tissue use," including bone repair, he adds.
Illustration: The small, sea-dwelling sandcastle worm normally makes its tube-shaped home by using its tentacles to grab pieces of sand and shell from the water and attaching them with its own natural glue. But in the laboratory, the worm will make its tube out of just about anything it is given – in the case of this photo, beads of zirconium oxide. A synthetic version of this seaworthy glue has been developed at the University of Utah for possible use in repairing small fragments of bone in people with fractured knee, wrist and other joint bones, and also facial bones. --Fred Hayes for the University of Utah.
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Abstract (Macromolecular Bioscience. 2009 May 13;9(5):464-71)
Abstract (238th American Chemical Society National Meeting, Washington, DC, 08/16-20/09. Presentation AGFD 80)