January 11, 2010 – Researchers at McMaster University in Canada have developed a way to direct microscopic-sized worms along a microchannel device using an electric field, seen as a step toward high-throughput microscreening devices for drug discovery.

The research, described in the Jan. 21 issue of Lab on A Chip, involves the nematode C. elegans, widely used in biomed research because of its similar proteins and molecules to those in humans. Typically the critters are manipulated in mediums of petri dishes, 96-well plates, or pneumatically controlled microfluidic devices. In the new work, the researchers guided the worms forward and in reverse inside a microchannel with an electric field ("electrotaxis"). Current practices observe worms under a microscope as they move randomly or in a direction forced by pressure; the new method lets the worms move in a more "natural" motion. Also among the findings was an observation that the worms’ response to electrotaxis was dependent on age and neuronal development — this, they say, allows for large numbers of worms to be sorted and handled in an automated manner.

The movement of worms in an electric field. (a) The application of +8 Vcm-1 electric field (E) caused an animal (724μm long) to move with the speed of 308μm s-1 to the right towards the cathode. (b) At a lower field strength in a reverse direction (-3 Vcm-1) the animal (847.5μm long) moved with a speed of 342μm s-1 to the left towards the cathode. Dark thick arrows illustrate the worm’s position. Scale bars are 1mm. (Source: McMaster University)

Implications for the work include more cost-effective ways of conduct rapid screening of tens of thousands of chemicals for drug candidate identification. Also, researchers can further study how neurons respond to electricity, and learn to fabricate new devices to handle and manipulate large numbers of worms.

"This is the first time that worms have been stimulated to move in a micro-channel device in a very precise and directed way," said Bhagwati Gupta, assistant professor of biology, in a statement. "It will allow researchers to study in real time how a proposed drug affects neurons and muscles that control motion of a live specimen."

From the abstract:

In this work, we demonstrate that the electric field can be used as a powerful stimulus to control movement of worms in a microfluidic environment. We found that this response (termed electrotaxis) is directional, fully penetrant and highly sensitive. The characterization of electrotaxis revealed that it is mediated by neuronal activity that varies with the age and size of animals. Although the speed of swimming is unaffected by changes in the electric field strength and direction, our results show that each developmental stage responds to a specific range of electric field with a specific speed. Finally, we provide evidence that the exposure to the electric field has no discernible effect on the ability of animals to survive and reproduce.