As reaction volumes in the liquid phase grow ever smaller, one has to ask about new reaction formats. SIMOA from Quanterix is a case in point where individual molecules are assayed in nanowells. Counting technology is used to estimate the concentration.
A recent report from MIT describes bioreactions in individual drops. The experimental format is a surface array of individually programmable microelectrodes. By controlling the frequency of individual electrodes, one can control movement. This avoids plumbing problems associated with microtubes and fittings. A short video shows individual drops moving to specific locations where they can collide and mix with other drops.
The surface of the plate is treated to eliminate tracks left after the drop passes to neighboring electrodes. The electrodes do not contact the sample drops.
Thus, one can mix minute quantities of reagent A with reagent B and incubate the intermediate drop for a set time and then introduce a third drop with reagent C and so on. The small volume promotes rapid mixing and reduces reagent and disposal issues.
The video targets air-driven pipettes with disposable tips as obsolete and wasteful. But it is not clear how the drops are delivered to the plate. However, once on the plate, the drops are well controlled. I saw no data on reproducibility and drop stability due to evaporation, etc.
It will be interesting to watch the adoption of this technology.
For more information visit https://www.media.mit.edu/projects/programmable-droplets/overview/.
Robert L. Stevenson, Ph.D., is Editor Emeritus, American Laboratory/Labcompare; e-mail: [email protected]
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