Journal
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
Volume 103, Issue 45, Pages 16677-16680Publisher
NATL ACAD SCIENCES
DOI: 10.1073/pnas.0607693103
Keywords
biosensors; electron transfer; gold electrode; methylene blue; signal-on
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Funding
- NIBIB NIH HHS [EB 002046, R01 EB002046] Funding Source: Medline
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We report a signal-on, electronic DNA (E-DNA) sensor that is label-free and achieves a subpicomolar detection limit. The sensor, which is based on a target-induced strand displacement mechanism, is composed of a capture probe attached by its 5' terminus to a gold electrode and a 5' methylene blue-modified signaling probe that is complementary at both its 3' and 5' termini to the capture probe. In the absence of target, hybridization between the capture and signaling probes minimizes contact between the methylene blue and electrode surface, limiting the observed redox current. Target hybridization displaces the 5' end of the signaling probe, generating a short, flexible single-stranded DNA element and producing up to a 7-fold increase in redox current. The observed signal gain is sufficient to achieve a demonstrated (not extrapolated) detection limit of 400 fM, which is among the best reported for single-step electronic DNA detection. Moreover, because sensor fabrication is straightforward, the approach appears to provide a ready alternative to the more cumbersome femtomolar electrochemical assays described to date.
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