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Mussel-Inspired Waterproof Adhesives Could Help Heal Wounds, Repair Ships

Researchers at Massachusetts Institute of Technology have designed new mussel-inspired waterproof adhesives that could be used to heal wounds or repair ships.

Combinatorial and modular genetic strategy for engineering self-assembling underwater adhesives; abbreviations: Mfps - mussel foot proteins (Mfp3 and Mfp5 - major mussel adhesive foot proteins, have unstructured coil structures in solution and are critical to the underwater interfacial adhesion of mussels); CsgA - an amyloidogenic protein that is the major subunit of adhesive curli fiber in Escherichia coli (contains five stacked strand–loop–strand motifs mediated by conserved residues and can self-assemble into nanofibers via a rate-limiting nucleation step followed by fibril extension). Image credit: Chao Zhong et al.

Combinatorial and modular genetic strategy for engineering self-assembling underwater adhesives; abbreviations: Mfps – mussel foot proteins (Mfp3 and Mfp5 – major mussel adhesive foot proteins, have unstructured coil structures in solution and are critical to the underwater interfacial adhesion of mussels); CsgA – an amyloidogenic protein that is the major subunit of adhesive curli fiber in Escherichia coli (contains five stacked strand–loop–strand motifs mediated by conserved residues and can self-assemble into nanofibers via a rate-limiting nucleation step followed by fibril extension). Image credit: Chao Zhong et al.

Mussels secrete very sticky substance that helps them cling to rocks or ship hulls. The substance is made of several proteins known as mussel foot proteins.

Inspired by this natural adhesive, the scientists engineered the common gut bacteria Escherichia coli to produce a hybrid material that incorporates sticky proteins of the Mediterranean mussel (Mytilus galloprovincialis) and bacterial proteins found in biofilms. When combined, these proteins form even stronger underwater adhesives than those secreted by mussels.

Prof Timothy Lu, a team member and the senior author on the paper published in the journal Nature Nanotechnology, explained: “the ultimate goal for us is to set up a platform where we can start building materials that combine multiple different functional domains together and to see if that gives us better materials performance.”

Scientists have previously used Escherichia coli to produce individual mussel foot proteins, but these materials do not capture the complexity of the natural adhesives.

The bacteria engineered by Prof Lu and his colleagues produce two different mussel foot proteins, combined with bacterial proteins called curli fibers.

After purifying these proteins from Escherichia coli, the researchers let them incubate and form dense, fibrous meshes.

The resulting material has a regular yet flexible structure that binds strongly to both dry and wet surfaces.

“Adhesives assembled from equal amounts of mussel foot protein 3 and mussel foot protein 5 formed stronger adhesives than those with a different ratio, or only one of the two proteins on their own,” the scientists said.

“These adhesives were also stronger than naturally occurring mussel adhesives, and they are the strongest biologically inspired, protein-based underwater adhesives reported to date.”

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Chao Zhong et al. Strong underwater adhesives made by self-assembling multi-protein nanofibres. Nature Nanotechnology, published online September 21, 2014; doi: 10.1038/nnano.2014.199