Sea Anemone Stingers Deliver Drugs

Oct. 23, 2006 — A future drug-delivery method could come from a surprising source: the stinging cells of sea anemones and jellyfish.

The method, developed by Israel-based NanoCyte, has been demonstrated effective for delivering anesthesia and insulin for diabetes, but has additional applications for treating acne, wrinkles and perhaps even painting pain-free tattoos. Its developers hope to bring it to market by 2007.

"The NanoCyte technology was tested on over 100 volunteers with no sensation at all," said Tamar Lotan, founder and president of the company.

The researchers got their inspiration for the technique, in part, from nature.

Sea slugs that feed on jellyfish and sea anemone often remove the stinging cells from their prey, mount them to their own skin, and use them for defense.

"NanoCyte is taking advantage of 500 million years of engineering work done by nature. So in essence nature has paid a lot of the R and D costs," said Rob Steele, a chemist at the University of California, Irvine. Steele is not involved with the research.

Whether on a jellyfish or a sea anemone, the cells work the same way when the animal attacks its prey. Microcapsules inside the cells shoot out tiny hollow threads that penetrate the victim and deliver a toxin.

About 15,000 species carry the stinging microcapsules, but only a few dozen are harmful to humans.

Lotan and her team removed the microcapsules from a sea anemone only toxic to some plankton, first "milking" the capsules from filaments on a sea anemone. The process does not harm the creature and is similar to milking a cow, said Lotan.

Next, they neutralized the content inside microcapsules, and then dehydrated them.

When the dried microcapsules come into contact with a liquid drug solution, the pressure of rehydration forces them to shoot out the tiny threads. At the same time, the capsule sucks in drug content from one end and pumps it through the thread.

The trick is to prevent the liquid drug solution from activating the dried microcapsules until it's needed by the patient.

The scientists have several solutions. One is a drug patch that contains a membrane between the microcapsule layer and the drug layer. When the patch is applied to the skin, the membrane breaks, mixing the two ingredients.

Another is a dual chamber tube that keeps the microcapsules and the drug separated until they are both squeezed onto the skin.

Thousands of stinging cells injecting a drug may not sound like a painless affair, but because the threads are less than 1 micron across, the patient does not feel them. By comparison, the smallest needle is 500 microns in diameter.

According to Steele, using something a microcapsule-based "needle" might cause an allergic reaction.

"The needle in this case is protein rather than metal, so it seems possible that the immune system might develop a reaction against it," said Steele.

However, the researchers tested repeated application on humans with no such reactions reported.