Porcupine Quills Inspire Medical Devices

The tip of a single quill on a North American porcupine holds as many as 700 backwards-facing barbs that can lodge into the flesh of any animal that wanders too close.

For the first time, scientists have figured out how those barbs work together to make it is so easy for quills to penetrate tissue but so hard to pull them out.

The discovery could inspire a slew of useful medical devices, including needles that hurt less going in or adhesive patches that would prevent gut leakage after gastric bypass surgeries and related procedures. Already, the researchers have created model quills that work like their natural counterparts.

"We're constantly looking to nature for examples that can inspire new approaches toward solving medical problems," said Jeffrey Karp, a bioengineer at Brigham and Women’s Hospital in Cambridge, Mass. "I really think evolution is the best problem-solver."

Porcupines are slow-moving creatures that lack the speed to run away from predators. Instead, defense comes in the form of some 30,000 quills that cover the back of each animal. And it doesn’t take much pressure for the quills to leave a porcupine’s body and enter the tissue of its attacker.

Scientists have long known that North American porcupine quills have barbs on their ends that make post-attack removal difficult and painful. To better understand how the quills pack their punch, Karp and colleagues inserted gently removed quills into a variety of targets, including chicken muscles, pig skin and synthetic human skin.

Using a mechanical tester, the researchers found that it took much less force than expected for the quills to penetrate tissues and more force than expected to pull them out, the team reports today in the Proceedings of the National Academy of Sciences.

The barbs, which cover just the last four millimeters (0.2 inches) of each quill’s tip, proved to be essential. When the researchers painstakingly removed barbs from quills, tests showed that it took more force for penetration to occur and less force for ejection.

Removing just some of the barbs showed that the hooks at the very last millimeter of the tip were most important for stickiness. But all of the barbs seem to work cooperatively.

As a last step, the researchers used plastic to mold model quills, which behaved just like the porcupine-made versions. That opens the way to developing medical applications. By isolating the ease with which quills penetrate skin and muscle, for example, scientists could develop porcupine-inspired needles that cause less pain.

The team also used their synthetic quills to create a barbed patch, which stuck well to tissues. Compared with a barbless-patch, it required 30 times more force to remove.

Read more at Discovery News