Cleaning up oil spills with mussel power

The chemicals that enable mussels to cling to rocks and boat hulls may soon provide a solution for cleaning up oil spills and purifying water.

Writing in the journal Matter, scientists from China and the US outline a range of engineering research initiatives inspired by the humble mussel, ranging from solar steam generation to removing heavy metals from wastewater.

“Mussels are broadly regarded as a nuisance in marine industries because they will colonise submerged surfaces,” says Hao-Cheng Yang from Sun Yat-sen University, China. 

But it is just this ability of mussels to form a robust underwater attachment to other surfaces that has inspired scientists to tackle a range of problems by mimicking their biochemistry.

Mussels withstand powerful currents and forceful waves by attaching themselves to rocks using clusters of thin, surprisingly hardy byssal threads – a bundle of secreted filaments more commonly known as the beard.

These threads owe their adhesive power to an amino acid group called dihydroxyphenylalanine (DOPA), which clings to surfaces by performing molecular gymnastics, including hydrogen bonds and hydrophobic and electrostatic interactions. 

Scientists have found that DOPA can adhere to all sorts of surfaces through these interactions – and so can its sibling chemicals dopamine and polydopamine (PDA).

The researchers report that this property has spurred the growth of mussel-inspired chemistry as a powerful new tool for material surface engineering and environmental science.

For example, engineers are developing new methods for separating oil and water with a “superwetting” agent that uses the adhesive action of mussel chemicals to clear the liquids away from each other.

“Oil spills and petroleum-based pollution are an ongoing global challenge to the marine environment and ecosystem,” the authors write. “Traditional membranes and adsorbents cannot meet the growing demand for effective oil/water separation.”

Researchers believe this mussel-driven innovation may be suitable for large-scale production, with potential to reduce environmental damage to marine environments after oil spills.

Mussels have also inspired advancement in water purification technology. Innovative materials able to remove heavy metals, organic pollutants and pathogens from wastewater are being developed from PDA, which easily binds to such contaminants.

Scientists also are working on the extraordinary ability of PDA to convert light into heat. PDA can absorb 99% of photon energy and convert it into heat within a few trillionths of a second, which could be used to create a flexible, scalable, and completely biodegradable photothermal evaporator for highly efficient solar steam generation.

Challenges still must be overcome before these innovations can be applied in the real world.

Scientists are still working to understand fully the properties of mussel-inspired chemicals, and to understand the complex interactions between amino acids that influence their adhesive properties.

“Looking forward, mussel-inspired chemistry has exciting potential for integration with emerging technologies such as 3D printing to design high-performance functional materials combining unprecedented control over both structure and interfacial properties,” the scientists conclude.