A simple microfluidic system for growing cells in concentration gradients will be useful for testing anticancer drugs and studying stem cell development, say researchers from Korea.

Sang-Hoon Lee and colleagues from Korea University in Seoul have developed a technique that uses osmosis to generate concentration gradients. The force of osmosis pumps two solutions into a channel, and at the interface where the solutions meet a gradient forms by diffusion of the solutes. Cells can be grown in the gradient to study effects of varying concentrations of external chemicals on their growth.

Osmosis forces two solutions into a channel to set up a concentration gradient in which cells are grown

Using osmosis to generate the gradient eliminates the need for bulky electric or pneumatic pumps. This makes this method easier to use and cheaper than current techniques, say the researchers.

Shuichi Takayama of the University of Michigan, in Ann Arbor, US, who also develops microfluidic systems for cell biology applications, is impressed that the technique can achieve flow rates as low as a few micrometres per second. This means that very broad gradients can be achieved as there is plenty of time for the chemicals to diffuse. 'Very slow flow that is continuous is actually quite hard to produce, and this is a nice way to do that,' said Takayama.

The researchers tested their method by growing human stem cells in a gradient of fetal bovine serum. The results showed that the serum enhances cell growth and proliferation, said Lee, which is in line with previous results.

Stem cell research is not the only field that will benefit from the technique though. Lee's group intends to try the system in various areas where it has ongoing research, including testing the effects of anticancer drugs on cells and studying cell migration in response to external chemicals.

Danièle Gibney