Nov 24 2010
Electrical sensor arrays are useful tools for rapid and early diagnosis of cancer and other genetic diseases. Zhiqiang Gao and co-workers at the A*STAR Institute of Bioengineering and Nanotechnology have developed an array that can sense messenger RNA (mRNA) for quantitative gene expression profiling1.
Conventional gene expression profiling methods rely on the amplification of target DNA through polymerase chain reaction (PCR) technologies and the detection of fluorescent labels. However, these methods are expensive to run and have low throughput. The researchers designed a high-sensitivity PCR-free device that directly quantifies gene expression using a two-step hybridization of the target mRNA. “Our goal is to develop a highly portable molecular diagnostic system,” says Gao, who led the research group.
At the heart of this device is a pair of vertically aligned gold microelectrodes, separated by an insulating ‘nanogap’ and deposited onto a silicon chip using standard photolithography. After anchoring polythymine probes complementary to the mRNA polyadenine tails on the top microelectrodes, they attached target-specific ‘capture probes’ on the bottom microelectrodes. Hybridization of the target mRNA extremities with the immobilized probes bridged the nanogap. Finally, the team coated the resulting mRNA–DNA complex with silver to generate a conducting wire between the electrodes for signal detection
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