As reported by Nanotechweb.org: Researchers at Arizona State University in the US say that they have made a new molecular reader that might be able to sequence DNA. The device works by capturing molecules in a hole cut into a layered tunnel junction. The work is part of a global effort to develop speedy, low-cost methods to read DNA nucleotides – the building blocks of life.
The fixed-gap layered tunnel junction developed by the ASU team is different in that the tunnel gap is defined by a dielectric, which the researchers grow on the device using a routine and well-known technique called atomic layer deposition (ALD). They then drill a hole through the layers using a process called reactive ion etching so that the tunnel junction can be exposed to molecules in solution.
When the metal electrodes making up the junction are functionalized with so-called recognition molecules that capture DNA nucleotides (thanks to hydrogen bonding), the team is able to identify individual nucleotides by measuring how the tunnel current fluctuates.
Full story here and publication below:
Pei Pang, Brian Alan Ashcroft, Weisi Song, Peiming Zhang, Sovan Biswas, Quan Qing, Jialing Yang, Robert J. Nemanich, Jingwei Bay, Joshua T. Smith, Kathleen Reuter, Venkat S. K. Balagurusamy, Yann Astier, Gustavo Stolovitzky, and Stuart Lindsay
ACS Nano, Article ASAP, DOI: 10.1021/nn505356g, Publication Date (Web): November 7, 2014
Previous measurements of the electronic conductance of DNA nucleotides or amino acids have used tunnel junctions in which the gap is mechanically adjusted, such as scanning tunneling microscopes or mechanically controllable break junctions. Fixed-junction devices have, at best, detected the passage of whole DNA molecules without yielding chemical information. Here, we report on a layered tunnel junction in which the tunnel gap is defined by a dielectric layer, deposited by atomic layer deposition. Reactive ion etching is used to drill a hole through the layers so that the tunnel junction can be exposed to molecules in solution. When the metal electrodes are functionalized with recognition molecules that capture DNA nucleotides via hydrogen bonds, the identities of the individual nucleotides are revealed by characteristic features of the fluctuating tunnel current associated with single-molecule binding events.
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