Immunology

A new medical-testing device is being prepped to enter the battle against infectious disease. This instrument could improve diagnosis of certain diseases in remote areas, thanks in part to knowledge gained from a series of investigations aboard the International Space Station on the behavior of liquids. The device uses the space-tested concept of capillary flow to diagnose infectious diseases such as HIV/AIDS and tuberculosis.

David Kelso, Ph.D., a researcher at Northwestern University in Evanston, Ill., had been working for several years to develop a simple, inexpensive device that could be used in resource-limited settings to test for infectious diseases. When designs didn't work as expected in the lab, Kelso brought in Portland State University researcher Mark Weislogel, Ph.D., who is the principal investigator for the Capillary Flow Experiment (CFE) on the space station.

"He came by the lab, we ran two or three experiments for him, and he explained to us that the problem had to do with capillary flow," Kelso says. "Our mindset was that gravity would pull fluids through the device, but his mindset, due to his work in microgravity, was to use capillary action. His experience and work in zero-G was invaluable; he could look at something and not be constrained to just seeing the effects of gravity but other effects that we were blind to."

Cell samples in the form of blood or other bodily fluids are put into the device, where an enzyme fluid bursts the cells to release DNA or RNA. Another solution washes away the enzyme and the cellular debris, leaving behind the DNA or RNA, which is captured on a bead and used to identify infectious viruses. "You only need fewer than a dozen particles, and you can detect the presence of the virus," Kelso explains. "It's a phenomenal analytical technique, but it involves four different fluids that have to be moved around."

That's where capillary forces come into play. The interaction between a liquid and a solid that draws a fluid up a narrow tube, capillary forces continue to operate in microgravity, and the low-gravity environment on the space station enabled researchers to conduct investigations into the special dynamics of this fluid behavior. The CFE series clarified the properties of the boundary between a liquid and the solid surface of its container and the flow of liquids under certain conditions. This knowledge will prove useful in designing fluid-bearing containers such as propellant tanks and water storage and management systems. It also will aid in creating instruments that use bio-fluids - including the medical testing device the Northwestern lab is developing.