Mussels' Tenacious, Sticky Threads Could Create New Era of Medical Materials

Mussels cling onto hard surfaces, tiny strands grabbing tenaciously onto rough rocks and cement. Despite being battered by waves and tides, these creatures continue to remain latched onto their chosen home. Now, scientists have uncovered exactly how mussels accomplish this feat. They've revealed the secret behind a mussel's threads, which could allow them to create new medical materials.

Known as byssus threads, the fine filaments that mussels use to attached themselves to the surfaces of rocks, piers or ships allow them to drift further out into the water. This, in turn, gives the mussels the advantage they need to filter nutrients in the ocean. Despite looking thin and fragile, though, these byssus threats are extremely tough, withstanding impacts from ocean waves.

In order to unwind the secrets of these threats, though, the researchers had to employ computer models and laboratory tests. They placed an underwater cage in Boston Harbor for three weeks. During this time, mussels attached themselves to the surfaces of glass, ceramics, wood and clay in the cage. Then, the scientists mounted the mussels, threads and substrates in a tensile machine in their lab. This machine was designed to test the mussels' strength by pulling on them with controlled deformation and then recording the applied force during the deformation.

It turned out that the distribution of stiffness in the mussels' threads allowed them to be subjected to very large impact forces from waves. About 80 percent of the length of byssus threads is made of stiff material while about 20 percent is made of softer and stretchier material. The softer material attached to the mussel itself while the stiffer portion attached to the rock.

This 80-20 ratio was crucial of the mussels' success. Having more of the soft material increased the reaction force since it couldn't effective slow down deformation, for example. The ratio, in other words, led to the smallest reaction force.

"Like the rest of the field, I certainly never suspected an architectural features of the byssi themselves to be so central to the dynamic resilience of these organisms," said Guy Genin, a professor of mechanical engineering and materials science at Washington University who was not involved in the study, in a news release. "The magic of this organism lies in the structurally clever integration of this compliant region with the stiff region."

The findings aren't just interesting when it comes to knowing more about these sea creatures, though. Understanding how mussels cling to hard surfaces could allow researchers design better, stronger materials. For example, surgical sutures used in blood vessels or intestines can be subjugated to pulsating or irregular flows of liquid-like waves in an ocean. By potentially creating materials that mimic the byssus threads, scientists could make these sutures safer for patients.

The findings are published in the journal Nature Communications.