Fascinating Sandcastle Worm Inspires Biocompatible Glue For Broken Bones
Let me introduce you to Phragmatopoma californica, the sandcastle worm, if you haven't already met. This incredibly self-contained worm, found on the southern coast of California, not only gathers its own materials to build its home, but uses its own bio-produced cement to superglue the materials together, creating its own permanent honeycomb housing - under water!
Biomimicking the sandcastle worm's super glue has enabled Russell Stewart and fellow bioengineers at the University of Utah to create a biocompatible synthetic glue that can be used to repair small bone fractures and still enable the regeneration of natural bone tissue.
While larger bones and joints are generally put back together with special medical-grade nails, screws, pins, and wire, until they are ready to bear weight, smaller fractures are much more difficult to hold together with those methods. Thus, the search has been ongoing for a bio-adhesive that would not dissolve in body fluids or blood.
The sandcastle worm has dozens of tentacles that it uses to gather food and materials for home-building. To build its long-tunneled home, its tentacle cilia sweep up particles of sand and shell and send them down to the worm's pincer-like "building organ," near its mouth. Like a jeweler inspecting a gem, the worm studies the facets of the particles, turning them over with its tentacles and, if the worm is satisfied, "it carefully dabs the particle with adhesive from its cement glands and presses it into place in its tube home." (source) The worm checks the particle after several seconds to adjust it perfectly in place. If the particle is not satisfactory, the worm will place it "in storage," for perhaps later, it will find a better fit.
Here, photographer Peter J. Bryant captures colonies of the underwater sandcastle worms.
Even in the lab the sandcastle worm uses whatever is around to create a home for itself. In the short video below you can observe, as it builds a tunnel with pieces of silicon provided by the researchers.
The sandcastle worm's glue seems to have proven itself to be the glue to biomimick. Stewart and his colleagues have done so, making a synthetic glue that is twice as strong as the worm's glue, mimicking the natural glue's water solability, its ability to bond in water, and the timing of its adhesion in response to changes in the surrounding pH.
The new bio-glue was tested successfully on shattered cow bones from grocery stores. It still remains to be tested on live animals and humans, so it will probably be another 8 to 10 years before it is approved for actual use in surgeries.
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