Xiao Yi, Lubin Arica A, Baker Brian R, Plaxco Kevin W, Heeger Alan J
Department of Physics, Materials Department, Institute for Polymers and Organic Solids, University of California, Santa Barbara, CA 93106, USA.
Proc Natl Acad Sci U S A. 2006 Nov 7;103(45):16677-80. doi: 10.1073/pnas.0607693103. Epub 2006 Oct 25.
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.
我们报道了一种无需标记且检测限可达亚皮摩尔级别的信号开启型电子DNA（E-DNA）传感器。该传感器基于靶标诱导的链置换机制，由一个5'端连接到金电极上的“捕获探针”和一个5'端修饰有亚甲蓝的“信号探针”组成，信号探针的3'端和5'端均与捕获探针互补。在没有靶标的情况下，捕获探针与信号探针之间的杂交使亚甲蓝与电极表面的接触最小化，从而限制了观察到的氧化还原电流。靶标杂交会置换信号探针的5'端，产生一个短的、柔性的单链DNA元件，并使氧化还原电流增加多达7倍。观察到的信号增益足以实现400 fM的已证明（而非外推）检测限，这是单步电子DNA检测中报道的最佳结果之一。此外，由于传感器制造简单，该方法似乎为迄今为止描述的更为繁琐的飞摩尔级电化学检测提供了一种现成的替代方案。
