Scientists study porcupine quills to improve medical needles

Inspired by North American porcupine quills, scientists from Brigham and Women's Hospital in Boston hope to improve the design of medical needles.

The researchers have uncovered how these quills easily penetrate tissues and why, once lodged in flesh, are often difficult to remove.

In their study report published yesterday in Proceedings of the National Academy of Sciences, they say this discovery could prompt the design of medical needles that easily penetrate surfaces and resist buckling.

The North American porcupine has about 30,000 defensive quills on its back, which are released upon contact with predators. Contrary to popular belief, porcupines do not shoot their quills over great distances, says lead researcher Dr Jeffrey Karp of Harvard University.

The quills instead must penetrate tissue very easily and thus have evolved a specialised mechanism to achieve this. Each quill contains a conical black tip studded with a layer of microscopic, backward-facing barbs and a cylindrical base with smooth, scale-like structures. The quill's geometry enables it to penetrate tissue with ease, and once in the tissue, it consistently stays in.

The scientists used natural quills and replica moulded synthetic polyurethane quills to understand the physical forces at play when the quills penetrate and are removed from a variety of tissues, including muscle and skin. The quills can "strongly grip tissue with minimal depth of penetration - less than half a centimetre is enough - and they don't need to bend like staples to achieve secure fixation", says study co-author James Ankrum.