Worms' Paralysis Turned On and Off With Light

Rachel Kaufman
for National Geographic News
November 20, 2009

If Dr. Horrible really did have a "freeze ray," he might stop the world by zapping it with ultraviolet light, new research suggests.

Watch video of the nematodes' paralysis and recovery


After feeding a light-sensitive chemical to transparent, microscopic worms called nematodes, scientists at Simon Fraser University in British Columbia were able to paralyze the tiny creatures by exposing them to UV light.

The paralysis works because UV light changes the structure of the ingested chemical, called dithienylethene.

Upon UV exposure, the normally clear chemical turns blue, and it shuts down the worms' metabolism, said study co-author Neil R. Branda.

(See related pictures of blue-dyed rats that recovered from paralysis caused by spinal cord trauma.)

A shot of visible light restored the worms to normal, and the animals slowly began to wiggle around "as if they had never been paralyzed," the study authors say.

Light-Activated Drugs

The research marks the first time a light-activated "switch" has been successfully used on an animal for any application.

Mad scientists probably won't be paralyzing people this way anytime soon, in part because the chemical was eventually fatal to the worms.

But Branda and colleagues hope to one day use the technique to create drugs that can be switched on and off at will.

(Find out how maggots are being used in hospitals to treat wounds. Video.)

Currently doctors use light-sensitive materials to treat a variety of diseases, including certain forms of cancer. Existing treatments, however, can't be turned off once they've been activated.

With the new chemical, a drug distributed evenly throughout the body could be turned on "by shining a light on the specific part of the body you wanted [to medicate]," Branda said. A burst of different light would then stop the drug.

Such a treatment option could allow patients to easily control their own medications, he added.

"I don't see a reason why, if the light is very gentle, we're not going to have home kits."

Findings published online October 7 in the Journal of the American Chemical Society.

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