Handheld Pathogen Sensor Could Diagnose HIV in 30 Minutes

Two techs are better than one

By Clay Dillow 

Chaining Synthetic DNA to Detect Pathogens Two Y-shaped structures of synthetic DNA attach themselves to the target molecule in different places. From there, the other two arms of the "Y" can link with other similar DNA structures, causing pathogens to chain together into easily detectable clumps. Cornell

Working with support of the Bill & Medlinda Gates Foundation’s Grand Challenge to develop field-worthy point-of-care diagnostics for the developing world, a couple of Cornell researchers are mashing up their individual inventions to create a handheld pathogen detector that can quickly diagnose pathogens ranging from chlamydia and tuberculosis to HIV.
The portable device is a blend of a synthetic DNA tagging technology developed by Cornell biological and environmental engineering prof Dan Luo and a CMOS chip developed by Edwin Kan, an electrical and computer engineering professor. Luo’s technology does the actual detecting, while Kan’s chip is able to identify and respond to the amplified signals generated by the sensor. The result: a handheld disease targeting machine that can diagnose pathogens in half an hour rather than days.

The sensor works via Y-shaped segments of synthetic DNA that Luo’s research group devised. At the bottom of the Y the team installed antibody designed to target and lock onto a certain pathogen. On one of the upper arms it placed a molecule that will link up with other similar molecules in the presence of UV light. In practice, two slightly different Y-structures are introduced to a sample, where they attach themselves to opposite sides of any target pathogen molecule they come in contact with. But tiny strands of Y-shaped DNA attaching themselves to a single molecule doesn’t send a very strong signal--the entire combined structure is still so small that only highly tuned and very precise sensors or microscopes could detect that the DNA had attached itself to the pathogen at all. But if you have a bunch of DNA structures attached to a bunch of pathogen molecules, the signal is clearly amplified. As such, the handheld sensor will bathe samples in UV light causing the DNA structures to begin binding together in a chain that is far easier to detect than a single pathogen molecule or a single DNA structure. Kan’s sensor chip can then measure both the mass and charge of molecules that come in contact with it. From those measurements, the chip can tell whether the synthetic DNA chain is towing pathogen particles along with it--and thus if they are present in the sample or not.
Add some nanofluidics and a power source to the mix, and you basically have an inexpensive handheld diagnostic device ready to go to work far from the convenience of hospitals and well-stocked medical labs. Further tests will ensure that the system is durable enough to take a beating out in the field and still return valid diagnostic results. More via Cornell.