In the past researchers developed many different microrobots for the mechanical studies of single cells. Some of them require complicated micromanipulators; others can be controlled with optical tweezers, but are limited in the force that they exert and so are inapplicable to cells with stiff cell walls.
A team from institutes in the USA and Japan, including MIT and RIKEN, describes in a recent Lab Chip article a new type of microrobot that can be installed in a microfluidic chip and used for mechanical stimulation of single cells. In this device a robotic arm with a mechanical probe at its end is built from a magnetic material and can be moved within the structure of the microchip by applying magnetic force. This design means that there are no complex mechanical assemblies necessary to move the arm. The probe itself consists of a microneedle placed on a flexible base. The force applied with the needle is measured by the extent of base deformation.
Tomohiro Kawahara and colleagues built a microchip with the microrobotic probe in its main chamber and use it to study the reaction of small single-cellular organisms, diatoms, to mechanical stimulus. They are able to adjust the applied force so that the cell itself isn’t damaged. Upon stimulation they observe agglomeration of chloroplasts into two separate groups. They also quantify the stimulus required for chloroplast assembly to occur.
Although the experiment described by Kawahara and colleagues is a simple proof-of-concept, it does mean that a wealth of phenomena can now be examined in more detail than ever before. Another example where mechanical stimulus elicits a response is in the small organism dinoflagellate, which bioluminesces when mechanically probed. The response of many cells to this sort of stimulus mimics their response to attack by pathogens and Miyawaki’s microrobot now opens the way to studying such responses.
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On-chip microrobot for investigating the response of aquatic microorganisms to mechanical stimulation
Tomohiro Kawahara, Masakuni Sugita, Masaya Hagiwara, Fumihito Arai, Hiroyuki Kawano, Ikuko Shihira-Ishikawa and Atsushi Miyawaki
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Published on behalf of Rafal Marszalek, Molecular BioSystems web science writer. Rafal is an Assistant Editor of Genome Biology at BioMed Central