New Chemistry Method Uses "Test Tubes" Smaller Than the Width of a Hair

Using a water droplet 1 trillion times smaller than a liter of club soda as a sort of nanoscale test tube, a University of Washington scientist is conducting chemical analysis and experimentation at unprecedented tiny scales.

Top image shows an arrow pointing to target as a water droplet forms in oil. Bottom image shows an organelle called a mitochondrion after it has been encapsulated in the water droplet.

The method captures a single cell, or even a small sub-cellular structure called an organelle, within a droplet. It then employs a powerful laser microscope to study the contents and examine chemical processes, and a laser beam is used to manipulate the cell or even just a few molecules, combining them with other molecules to form new substances.

"Anything you can do in the test tube we hope to be able to do in the droplet. We just don't need a lot of cells. We don't even need one cell, just a few molecules," said Daniel Chiu, a UW associate chemistry professor who is developing the method.

The new approach makes it easier to get a wide range of information about a cell. Researchers typically use microscopy to see how proteins move within a cell and collect spatial information, but that provides very little biochemical information. Likewise, they can use large amounts of material in a test tube to understand biochemical processes, but that doesn't provide the fine detail of microscopy.

The new method, employing a process called microfluidics, allows researchers to perform chemical analysis and to study structure and form at the same time.

The tiny droplet is contained in a microfluidic device, which is mounted on a platform about the size of a dime. The device has water in one channel and oil in an adjoining channel. The target – a cell, an organelle, or just a few molecules -- is placed at the interface between the oil and water using a laser beam, so the target is encapsulated as the water droplet is formed.

Once the droplet captures its target, it is held fast while researchers use lasers to manipulate it and conduct analysis and experimentation.

According to the researchers, the new method allows researchers to address specific biological questions that cannot be answered by testing in large quantities in the test tube, such as how organelles within a cell differ from each other, or how different proteins are expressed within the same cell.

Currently Chiu is focused on continuing development of the process, essentially creating a nanoscale test tube. But he believes the process holds great promise for future chemical and biological research.

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