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Portable device to detect pathogens in 30 minutes

The goal: A handheld device, described as a molecular-level Lego set, that will test for tuberculosis and similar bugs in 30 minutes.

Engineers at Cornell are building a handheld pathogen detector that will help health care workers around the world test for pathogens such as tuberculosis, gonorrhea, and HIV and get results in as little as 30 minutes, instead of waiting days.

Single strands of DNA link up in the presence of a pathogen to form large chains and clusters, whose larger masses and charges are quickly detectable by the new chip. Luo Lab/Cornell

Dan Luo, professor of biological and environmental engineering, has been using synthetic DNA to amplify tiny samples of pathogen DNA, RNA, or proteins. Because of $25 million in funding from the Bill & Melinda Gates Foundation's Grand Challenge to 12 teams developing point-of-care diagnostics, Luo will be combining forces with Edwin Kan, a Cornell professor of electrical and computer engineering, who has built a computer chip that can respond quickly to those amplified samples.

The engineers describe their novel device as something akin to a molecular-level Lego builder. Because single strands of DNA pair up with others that have complementary genetic codes, the engineers can synthesize strands that will match others--even matching over only specific parts of their lengths--thereby assembling specific and even odd shapes.

Luo and Kan's pathogen detector uses a "Y" shape, with a DNA strand or antibody attached to the base of the Y designed to lock onto a pathogen, and a molecule attached to one of the upper arms that will chain up with similar molecules (polymerize) in the presence of ultraviolet light.

This means that by exposing a sample that includes this Y-DNA and a pathogen (such as tuberculosis) to UV light, the molecules at the upper arms will link up, forming long chains of Ys should the pathogen be present, which then group together into even larger masses. (This process is called a polymer chain reaction, or PCR for short.)

The chip, then, measures the sample's mass and charge. With a pathogen present, the resulting chain reaction is easily detected via its greater mass and charge; lower masses and charges indicate no chain reaction, and thus the absence of a pathogen.

The chip could conceivably be controlled by a cell phone. Once fast and affordable detection is possible, the task at hand is for the engineers to design a kit for the developing world that can function in extreme weather conditions.