January 8, 2007
Microfluidics Yield Rapid Gene Tests from Blood
In an accomplishment that represents a significant step toward an era of rapid, inexpensive, bedside testing for cancer, researchers at the University of Virginia have developed a microfluidic device that can process human blood samples and yield diagnostic results within an hour. The investigators, led by James Landers, Ph.D., have used the device to develop 30-minute tests for bacterial infections and a 60-minute test for lymphoma.
Reporting their work in the Proceedings of the National Academy of Sciences USA, Landers and his colleagues were able to link on a single glass slide individual microfluidic components needed to remove DNA from blood, amplify the DNA using polymerase chain reaction (PCR), purify the amplified DNA using electrophoresis, and detect specific DNA sequences of diagnostic importance. While Landers and other researchers had previously designed the components needed to conduct each step of this analysis, no one had managed to put them all in one easy-to-make device.
The key to the success of this device, the researchers noted, was solving a problem that had thwarted other such integration efforts, namely that the chemicals used to purify DNA from blood are incompatible with PCR. Landers’ team overcame this obstacle by taking advantage of the unique flow properties of fluids in microfluidic channels in order to divert these chemical away from the PCR chamber and into a waste chamber. They also made extensive use of polymer valves developed by Richard Mathies, Ph.D., and his colleagues at the University of California, Berkeley, and credit the Mathies group for teaching them how to make and use these valves.
To keep costs low, the investigators made the microfluidic device itself as simple as possible. All injection ports, pumps, heaters, and optical detection components reside in a manifold that clamps around the glass microfluidic slide. Engineering work is now underway to develop a manifold suitable for use in clinical settings and eventual human clinical trials. The investigators, as well as researchers who did not participate in this study, note that this device should work for any gene-based assay for which a PCR primer exists or can be developed.
This work is detailed in a paper titled, “A fully integrated microfluidic genetic analysis system with sample-in-answer-out capability.” An investigator from the U.S. Food and Drug Administration also participated in this study. An abstract of this paper is available through PubMed.