Like a hypodermic needle, the proboscis injects fish, worms and other snails with venom that instantly paralyzes the prey. The venom's power comes from hundreds of thousands of short proteins, called peptides.
Since the 1990s, scientists have studied a few hundred of those peptides, called conotoxins, with the hope of tapping into their powers. So far, the U.S. Food and Drug Administration has approved one synthetic conotoxin, called Prialt, for the treatment of severe and chronic pain. Others are currently in clinical trials.
While these treatments work well, their biggest limitation is that they need to be injected directly into the spinal cord, often through a surgically implanted pump. That's because the body quickly breaks down swallowed conotoxins before they can reach the receptors they need to reach.
To develop a snail-inspired painkiller stable enough to be taken orally, Craik and colleagues drew inspiration from an African plant that's long been used by witchdoctors as a tea to speed up labor and childbirth. Chemical analyses showed that the active ingredient in the plant was a peptide with the unusual shape: a circle. That shape, it turned out, made it more stable than most peptides.
Based on those findings, Craik's team engineered a synthetic conotoxin. Then, they added a few extra amino acids in order to turn the peptide into a circle.....
