Clingy mussels could inspire new glues and plastics

Blue mussels spend their days being buffeted by crashing waves and currents, remaining tethered to the rocks - or their fellow mussels - thanks to the highly effective underwater glue which they produce.

Given that achieving adhesion in the presence of water is so challenging, scientists who are interested in producing effective adhesives for use in wet environments – such as within the body, for surgical or dental purposes – have turned to nature for inspiration.

In a new Science paper, a McGill-led team reports that, after a decade of work in the area, it has uncovered the cellular mechanisms by which mussels fabricate underwater adhesives.

“The specific mechanism by which mussels produce their adhesive has been shrouded in mystery until now because everything occurs hidden from view inside the mussel foot,” said Tobias Priemel, a PhD candidate. “To understand the mechanisms involved we applied advanced spectroscopic and microscopic techniques and developed an experimental approach that combined several advanced and basic methodologies from across biochemistry, chemistry, and materials science.”

By gathering information at a subcellular level using a range of spectroscopic and microscopic techniques, the researchers discovered that within the mussel foot – which is specialised for clinging to surfaces – there are micron-sized channels which funnel the substances that come together to make the glue.

Condensed fluid proteins in vesicles (tiny sacs) are secreted into the channels in which they combine with metal ions extracted from seawater. The metal ions, which are also stored in small vesicles, are slowly released in a carefully timed process, eventually curing the fluid protein into porous, adhesive plaque filaments.

The accumulation and use of vanadium ions is of particular interest to researchers, since only a few other organisms are known to hyperaccumulate vanadium. The researchers believe that it plays an important role in hardening the glue and are continuing to work in this area.

“Mussels can make their underwater adhesive within two to three minutes by mixing metal ions with the fluid proteins,” explained Professor Matthew Harrington, a chemist and senior author of the paper.

“It’s a matter of bringing together the right ingredients, under the right conditions using the right timing. The more we understand about the process, the better engineers will later be able to adapt these concepts for manufacturing bio-inspired materials.”