I’ve been fascinated by adhesives for a long time. More specifically, ever since graduating with a Ph.D. in organic chemistry and working on perfluorinated materials (ex: Teflon) for six years, I’ve been interested in how to prevent an item from sticking to a surface. There is huge demand for a technology which will prevent so-called “biofilms” (sticky colonies of bacteria) from forming on a surface. On naval vessels, these biofilms provide the perfect attachment point for barnacles and other sea organisms. The extra weight and drag from this “biofouling” crust can significantly increase fuel costs for the boat.
Although I have developed several patent pending technologies that address this issue, I’m always on the lookout for fresh approaches and new techniques which could be used to prevent oysters, barnacles, and the like from attaching themselves to ships. That’s why I was excited to read a recent article in the Journal of the American Chemical Society (Americas leading chemistry journal) that described how researchers from my alma mater (USC Columbia) have identified the chemicals used by oysters to attach themselves to surfaces.
The article describes how Prof. Burkett and his team studied freshly-collected oyster shells; specifically, they examined the material that held the oysters in a clump. Oyster shells are mainly calcium carbonate – chalk – and are normally the source of calcium supplements that you’d buy from the drugstore. While calcium carbonate does have some attributes that make it a good ingredient for a building material (basicity, solubility characteristics, etc) the researchers knew that the oyster-to-oyster adhesive had to have something extra, besides just the calcium. They found it: there is a significant amount of iron and cross-linked proteins in the adhesive.
Proteins are present in every animal; they’re long chains of amino acids, joined end to end in a chain that coils up into particular shapes. In the case of the oyster adhesives, the proteins are cross-linked. That means that unlike a plate of slippery spaghetti noodles (not a bad analogy for simple linear polymers), these materials are all chemically bound together – a big clump of “spaghetti”. This crosslinking, which incorporates the calcium carbonate and iron particles into the “pores” (empty spaces) of the crosslinked protein, is what gives the adhesive it’s power. It’s not too terribly different from concrete, as it uses a crosslinked, largely inorganic matrix. The result is a powerful, naturally-occurring adhesive.
This research is important because only through understanding how oysters and other sea life attaches to surfaces can a deterrent be designed. Chemists are rapidly gaining a deeper understanding of these rather complex natural adhesives, and our defenses against them are gaining in technological complexity as our knowledge grows. When you consider the U.S. Navy claim that “biofouling” of their vessels by oysters / muscles / barnacles raises their fuel cost by 40% (with the associated environmental impact of burning that much fuel), it’s easy to see how studying oyster adhesives is a valuable use of chemists’ time. I’m pretty excited about this recent paper, and I hope that other scientists put the results to good use.
The source of this article can be found at:
Burkett, et. al. “Oysters Produce an Organic−Inorganic Adhesive for Intertidal Reef Construction”. Journal of the American Chemical Society, 2010.