In order to develop a new microfluidic device that uses a stimulus to manipulate the movement of the nematodeCaenorhabditis elegans, the authors aimed to show that an electricalsignal can act as a powerful stimulus to precisely control and direct movement of the nematode in microchannels.
Background/further details
20 synchronizedCaenorhabditis elegans of various age and size, from larval stage L1 (ca. 250 µm long) to young adult (ca. 1 mm long), were loaded individually into the microchannels filled with buffer and positioned in the central section (2.5 cm away from each electrode) using a syringe pump. To rule out the influence of electrokinetic flows (electrophoresis as well as electroosmosis), additional experiments were performed with dead worms. Additionally, 11 worms were investigated on post-exposure effects (behavior, fertility, viability; 10 worms at 2-4 V/cm and one worm at 12 V/cm).
5 cm long microchannel, 300 µm wide and 80 µm deep was used to study the worm movement; inlet, connected to a syringe pump and one electrode on one end, and outlet and the second electrode on the other end of the channel; with the help of the syringe pump a single worm was driven through the outlet into the channel and to the middle of it; then the pump was turned off and the electric field was turned on, either in one or the other direction; speed and direction of worm movement was measured
The data showed that the response (electrotaxis) of older larvae and young adultanimals was directional (towards the cathode) and highly sensitive. The characterization of electrotaxis revealed that it was mediated by neuronal activity (investigated with the aid of transgenicmutants) that varies with the age and size of animals (probably due to mature nervous system and investigated via longer and shorter transgenic worms). Not all developmental stages of animals responded equally well within the same threshold range. While the effective range for L4 larvae was 4-10 V/cm, the adults appeared significantly more sensitive and had a lower response threshold (2-4 V/cm). Although the speed of swimming was unaffected by changes in the electric field strength and direction, the results showed that each developmental stage responded to a specific range of electric field with a specific speed. Finally, the findings provided evidence that the exposure to the electric field had no discernible effect on the ability of animals to survive and reproduce. This method has potential in precisely controlling, directing, and transporting worms in an efficient and automated manner. This opens up significant possibilities for high-throughput screening of Caenorhabditis elegans for drug discovery and other applications.
