August 29, 2005

Lab on a Swab

Researchers at the University of Michigan want testing for the influenza virus to be as easy as taking one's temperature.

By Sarah J. Heim

Imagine that a pandemic flu has broken out in Asia. An airplane carrying exposed passengers is traveling across the Pacific Ocean toward Los Angeles. One of them begins to cough, causing palpable fear to spread throughout the cabin.

Acting swiftly and efficiently, a flight attendant pulls a small device from the overhead compartment, takes a throat sample from the ailing passenger, and identifies the virus as the influenza. On landing, all the travelers are quarantined -- and the spread of the flu is thwarted.

It's a scenario that may become a reality in the not-too-distant future, thanks to a group of researchers who've been working on ways to derive genetic information from human DNA more efficiently.

Furthermore, if combined with a wireless network, it could track the spread of flu strains throughout the world.

It all began with a small device -- and a big idea.

In 1992, a multidisciplinary group at the University of Michigan started developing a lab-on-a-chip device, called a Genotyper, as a way to reduce the steps needed to glean genetic information from human DNA using microfabrication methods. (See Notebook for the lab-on-a-chip concept.)

DNA-derived information can be used in testing everything from whether a chicken is safe to eat, to the origin of a blood stain at a crime scene, or if a child has the influenza virus.

After several years of prototyping, Michigan researchers began to discuss potential applications of the Genotyper device, which is about the size of a TV remote control.

"The advantages are that [the Genotyper] is very portable," says Ronald G. Larson, chair of the chemical engineering department at Michigan. "It seemed ideal for doing on-the-spot genomics on viruses -- and influenza was a logical candidate."

So they began to build a device that can quickly identify the genetic makeup of the influenza virus.

Since influenza is an RNA virus, the RNA must be first converted to DNA before it can be amplified on the chip. In the process, called PCR (polymerase chain reaction), enzymes are released that digest, or cut, the DNA at certain points.

"The way the gene is cut or not cut depends on which flu gene you have," says Larson. The DNA fragments are then run through a gel and stained with fluorescent tags, allowing scientists to distinguish one flu strain from another, or to tell if a new strain has emerged.