Fast, cheap and portable – a new pathogen detection tool

Liquid crystals, the visual element in products like digital watches, computer monitors and mood rings, may help in the quest for early detection of disease-causing pathogens.

Developed by professor Nicholas Abbott and doctoral student Justin Skaife, chemical engineers at UW–Madison, the advance could be especially useful for detecting serious pathogens like foot and mouth disease, West Nile virus, cryptosporidum or E. coli. The Centers for Disease Control has cited early detection of pathogens as critical to staving off potential public health emergencies.

By using liquid crystals in combination with nanostructured surfaces, Abbott says his credit-card sized plastic chips possess the potential to offer rapid detection of a bacteria or virus. Liquid crystals make great optical amplifiers because their molecules tend to line up with each other over long distances, forming long strands of up to a million molecules, like a clutch of uncooked spaghetti.

When exposed to a specific pathogen, this tendency to organize will make the presence of microscopic bugs visible to the naked eye.

Abbott first noticed this phenomenon in 1998, when he published an article in the journal Science showing how liquid crystals can amplify the binding of proteins on surfaces. That advance could be useful, for example, in detecting antibodies and other proteins in blood samples without the need for labels. But this patent, filed a year later through WARF, shows that liquid crystals can also be used to detect entire organisms.

The inventors first use techniques of nanofabrication to alter the surface of their device with ridges and bumps that match the size of contours of a species of virus or bacteria. The next step is to expose the surface to a water or soil sample from the field. Then the liquid crystal surface is laid over the surface. If the pathogen is in the sample, the liquid crystals will respond by changing their color or brightness, in the same way a computer monitor reacts to electrical fields or a mood ring reacts to temperature.

“We’re seeing an increasing focus on food pathogens and emerging diseases, especially with the greater movement of people and products around the world,” Abbott says. “We really don’t have methods of detection in use now that are rapid, robust and inexpensive.”