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Better Bonds from Mollusk Chemistry
By: Katie Schaefer, Cosmetics & Toiletries magazine
Posted: November 30, 2010, from the December 2010 issue of Cosmetics & Toiletries.
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Wilker and his team hypothesize that the consistencies of the mollusks’ adhesives differ based on the materials that they must hold together. “Oysters are externally sticking a hard shell to another hard shell, or hard shell to a hard rock—so maybe it is best to have a hard material. Whereas mussels are sticking a hard rock to the soft insides of the rest of the mussel,” said Wilker.
Since only a small amount of adhesive can be extracted from oysters and mussels, the team is producing the materials on a larger scale synthetically. “We are making synthetic versions of the adhesives to gain access to larger quantities . . . to be able to tailor the adhesive to its specific application,” said Wilker.
He explained that proteins cannot easily be made on a large scale, so rather than using the proteins in the synthetic adhesive, the team has inserted the cross-linking chemistry from the animals into bulk polymers. “If we extract the proteins from the animals, we can make 25 mg of the adhesive on a good day; if we put the mussel chemistry into a polymer backbone, we can synthesize 25 g on a good day,” explained Wilker, noting that the scale-up is 1,000 times more. The synthetic adhesive currently is only produced to mimic the mussel adhesive but the team plans to synthesize the oyster adhesive as well in the future.
There are two places where new adhesive materials are in demand, according to Wilker: for bonding wet tissue, i.e. surgical adhesives that seal wounds and incisions by bonding skin together; and in orthopedics, to act as bone cement or bone fill. Wilker notes that while there currently are some adhesives available that close wounds, they are often toxic.
According to Wilker, the three things one must look for in a medical adhesive are: “it must set in a wet environment, it must make strong bonds and it must be non-toxic.” He added that some materials will provide one or two of these benefits but not all three. “We hope our synthetic adhesive will do all three,” emphasized Wilker.