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Posted: Jan 05, 2012

New nano-biosensor could bolster early-stage disease detection and water monitoring

(Nanowerk News) A quick, inexpensive and highly sensitive test that identifies early-stage disease markers or other molecules in low-concentrations, could be the result of a new nanomechanical biosensor developed at Cornell.
The biosensor, based on a photonic crystal nanowire array, was developed by Yuerui Lu, a graduate student in the lab of Amit Lal, professor of electrical and computer engineering. Their research was published online in the journal Nature Communications in December ("Low-concentration mechanical biosensor based on a photonic crystal nanowire array").
It's so sensitive, the detector can hunt a few molecules in a glass of water. The experimental device is a mechanical resonator 50 microns in diameter made of a thin silicon-silicon dioxide membrane with ordered, tightly packed vertical nanowires on top. The design achieves a high surface-to-volume ratio for biomolecule detection, which means it can detect molecules at very low down to femtomolar concentrations.
The sensor works by attaching single-stranded probe DNA molecules onto the nanowires. When those molecules come into contact with a target single-stranded DNA, the relevant molecules bind together, changing the mass detected by the device. The mass change causes a change in the resonance frequency of the device.
A laser beam shines on the device, and the nanowires' innovative design allows for more than 90 percent absorption of the light, resulting in an efficient opto-thermo-mechanical excitation of the resonator. An optical readout of the resonance frequency change can be accomplished remotely, quickly and free of electrical wires, making the device convenient and inexpensive to make, the researchers said.
Society could have many uses for the biosensor: Lal said he imagines doctors could use such a device in clinical analysis, for example, in DNA testing. Typically today, DNA in drawn blood is compared against a standard sequence. The new device could instead be coded with particular DNA sequences of relevance, and those specific molecules could be detected in early stages when concentrations are low.
"You could have a cartridge with an array of the membrane sensors, and you could quickly scan to see what DNA imperfection you might have," he said. "Today's tests take time and are expensive."
Such sensors could also be useful for environmental applications, such as water quality monitoring. The researchers hope to improve their device by making it sensitive to certain protein molecules, which are trickier because they do not bind as specifically as DNA molecules do.
The DARPA (Defense Advanced Research Projects Agency) Microsystems Technology Office funded the research.
Source: Cornell University
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