July 24, 2013
Mussels Could Help Create Artificial Tendons
Michael Harper for redOrbit.com - Your Universe Online
MIT researchers have discovered precisely why mussels are able to stick to slick surfaces so well, even when faced with stiff currents and rocking waves. And beyond unraveling one more of nature's little secrets, the researchers believe they can use this information to help repair human tendons.
Mussels use filaments called byssus threads to adhere to piers, rocks and more. These byssus threads allow the mussels to stray out a little farther into the water than their pier-dwelling neighbors, the barnacle, thus giving them the ability to obtain more nutrients. While highly flexible, the byssus threads are also remarkably strong - a peculiarity that inspired MIT research scientist Zhao Qin and professor of civil and environmental engineering Markus Buehler to wonder if they could unlock the mystery of the byssus thread and apply it elsewhere.
The researchers now suggest that synthetic materials made like byssus threads could be used as sutures after surgery, to create artificial tendons, or even attach instruments to tall buildings. This research is set to appear in the upcoming edition of the journal Nature Communications.
Buehler and Qin compare a mussel's byssus threads to a bungee cord, noting that they allow for a lot of stretch and bend yet are still quite resilient. After investigating these threads, the pair discovered they are composed of a soft, stretchy material on one end and a more rigid material on the other. Though they have a slightly different texture and form, the threads are all made of a protein closely related to collagen, the same material found in bone, cartilage and tendons.
To understand the strength of the byssus threads and not the glue the mussels use to attach these threads to wet surfaces, Buehler and Qin captured mussels in an underwater cage in the Boston harbor. These bivalves attached themselves to ceramic, clay, glass and wooden surfaces which were placed in the cage. The team then brought the mussels back to the lab to test the tensile strength of the threads.
"Many researchers have studied mussel glue before," said Qin in a statement.
Though this glue is responsible for keeping the threads attached to the surface, Qin points out that it's the actual threads that give the mussels their stubborn stickiness. Though the glue holds the mussel firmly to the pier, it is not strong enough to keep the mussel attached through a round of pummeling waves.
The team then discovered that the stiffer end of the byssus thread takes up about 80 percent of the entire strand. The remaining 20 percent is composed of the softer, stretchier material found on the other end. Though the stretchy part of the thread makes up a smaller amount of the entire strand, Qin says it is the most crucial element in keeping a mussel attached to a surface.
"This combination works like a well designed bungee cord, which can stop the fall of a person jumping from a great height - and do so gently enough to prevent injury, because the stiffer region of the cord slows down the fall, but the softer region tempers the slowing of the fall to be a gradual process," said Qin.
The MIT research duo now say a synthetic material with a similar 80-to-20 ratio could be used as surgical sutures, particularly when heart and stomach surgeries are performed. Such a flexible and secure material could withstand the irregular flows of liquid often found in the stomach. These materials could also be used to create synthetic tendons to repair or replace damaged tendons in humans.