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Nanotech News
Counting DNA Molecules with Nanocantilevers Like a tuning fork, nanoscale cantilevers vibrate at a characteristic frequency that depends on their makeup and size. Alter the tuning fork or the nanocantilever in any manner and that frequency will change. By capitalizing on this property, an international research team has used nanocantilevers to detect a single piece of DNA 1578 base pairs in length. This device was also capable of counting the number of DNA molecules bound to a single 90 nanometer-thick silicon nitride cantilever. The group, led by Harold Craighead, Ph.D., of Cornell University, determined that they can accurately determine when a molecule with mass of about 0.23 attograms (1 attogram = 10-18 gram) lands on an individual nanocantilever. To achieve maximum sensitivity, the investigators placed nanoscale gold dots at the very ends of the cantilevers. The gold dots acted as capture agents for sulfide-modified double-stranded DNA, though the researchers note that gold nanodots could be used to capture any biomolecule with a free sulfide group. Nanocantilevers without gold dots were not able to accurately distinguish between specific and non-specific binding. Scanning laser beams were used to measure the vibrational frequency of the cantilevers. The researchers noted that they have incorporated similar nanocantilevers into optically accessible nanochannels within a microfluidic device, and suggest that such a device could be used to detect individual DNA molecules of predefined sequence. If so, such a device could eliminate the need for PCR amplification for detection of defined DNA sequences, and thus simplify methods used to screen for specific gene sequences and mutations.
This work is detailed in a paper titled, "Enumeration of DNA Molecules Bound to a Nanomechanical Oscillator" that was published in the journal Nano Letters. Investigators from Tel Aviv University in Israel also participated in this study. An abstract of this paper is available at the journal's website.
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