Single cell research

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

The method captures a single cell, or even a small subcellular structure called an organelle, within a droplet.

It then employs a 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.

This nanoscale 'laboratory' is so minuscule that it covers just 1% of the width of a human hair, said Daniel Chiu, a UW associate chemistry professor who is developing the method.

"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," Chiu said.

The 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, Chiu said.

Likewise, they can use large quantities of material in a test tube to understand biochemical processes, but that doesn't provide the fine detail of microscopy.

"The cell is very small but it is very complex," Chiu said. "It has many hundreds of thousands of proteins. It is probably the ultimate nanomachine."

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 far too small to be seen with the naked eye and is mounted on a platform so researchers can carry it from one place to another. 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.