Mussels' Mighty Grip Inspires Dopamine-Based Glue

John Roach
for National Geographic News
October 18, 2007
The uncanny stickiness of mussels has inspired a brainy new approach to creating a universal adhesive coating, researchers say.

Mussels secrete a complex cocktail of proteins to latch on to just about any surface, explained study co-author Phillip Messersmith, a biomedical engineer at Northwestern University in Evanston, Illinois.

(Related: "Gecko, Mussel Powers Combined in New Sticky Adhesive" [July 18, 2007].)

Messersmith and colleagues found that the two most prominent ingredients in this cocktail are the same as those in dopamine, a chemical messenger in the brain.

So the researchers wanted to find out if they could use dopamine to make an adhesive coating that matches the mussels' natural stickiness.

First they added a drop of pure dopamine to a beaker of water that had the same acidity as seawater.

In this solution the dopamine molecules went through chemical changes that caused them to link together and form new, larger molecules known as polymers.

This so-called polydopamine substance was remarkably sticky, the researchers found. Any object put in the new solution got coated with a thin, adhesive film.

"It pretty much worked well on just about any material that we tried," Messersmith said. "It is really tremendously simple."

The results appear this week in the journal Science.

Changing Coats

The researchers found that the dopamine-based glue could be used to make a variety of additional materials stick to objects, creating a host of functional applications.

For example, applying certain materials over a sticky object could prevent an object from becoming contaminated—a handy feature for medical instruments.

Secondary exposure to a copper nitrate solution would give an object a metallic sheen, useful in electronics such as flexible displays.

In another application, water polluted with mercury or lead could be passed through a column of beads coated in the adhesive. The metals would stick to the beads, allowing clean water to flow out the other side.

(Read more about threats to the world's freshwater supplies.)

"Each of these applications involves pretty much the same first step but a different second step," Messersmith noted.

He and his colleagues are now trying to determine the limits of the technology and where to focus their development efforts.

Successful Simplicity

Herbert Waite is a marine biologist at the University of California, Santa Barbara, who studies how each ingredient in the mussels' protein cocktail comes together to make the mollusks so sticky.

He said Messersmith's team deserves credit for reducing the complex ingredients to "two very simple features" to make their sticky coating.

"It's nice that the mussel inspired it with its own highly evolved adhesive technology," he said, "but it isn't the same thing as mussel adhesion."

If a mussel just squirted dopamine, the chemical would simply diffuse into the large volume of surrounding seawater, he noted.

"What works for man would not have worked for the mussel."

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