Sticking To It

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The use of glues to stitch together external wounds is not new to modern medicine. But most glues used by physicians vary little from common household varieties and, as such, cannot be used internally, where they could cause inflammation. So the search for a medical adhesive that could be used inside our bodies continues. It would be a breakthrough for doctors to be able to use a safe, effective glue to patch together shattered bones or to close internal incisions.

Since the early 1980s, much attention has focused on the blue marine mussel, or Mytilus edulis, often seen clinging to boats, rocks and piers in tidal zones. This mollusc uses a glue that's not only strong and efficient, but works in sea water, a churning, wet and saline environment. "It's more or less the same environment as inside our bodies," notes Mieke C. van der Leeden, a physical chemist at the Delft University of Technology in The Netherlands.

But until now, the mussel's glue's physics remained a mystery. However, research led by van der Leeden has cracked that enigma, opening the way for an effort to synthesize the glue in a laboratory. Her team keyed on the Mytilus edulis foot protein 1 (Mefp-1) which resembles a bundle of wire, but stretches out once it's in contact with whatever it's adhering to. They also determined that for it to work properly it needs the right mix of oxygen and a high pH (low acidic) factor.

Van der Leeden has now involved polymer experts to help create a bioengineered version of the mussel glue. They are working with rather simple polymers, but the process also requires the use of special amino acids that are hard to handle. Another problem is that it's difficult to separate the Mefp-1 protein because it's so sticky it can gum up the equipment used to do the separation.

The resulting product needs be able to last an average of eight weeks, enough time for muscle or bone tissue to heal. And it needs to be biodegradable. "We also have to make sure that when the glue degrades it's not poisonous," van der Leeden says.

Since it's all so much trouble trying to recreate the glue in the lab, why not just extract it from the mussels and use the real thing? "That would be impossible," van der Leeden explains. "It would be time consuming and costly to do that on a large scale." It takes a huge amount of mussels to extract just one milligram of the glue. So commercial harvesting of the glue would soon decimate the mussel population.

Van der Leeden's team has enough funding to continue its efforts for another year. It needs to show some progress by then if it wants to attract further financial backing from the pharmaceutical industry. And van der Leeden admits she's not sure of success. If her team does succeed, the resulting glue would then have to undergo a series of tests and clinical trials. So even adhering to the most optimistic time frame, a commercial product is at least a decade away.