State Key Laboratory of Analytical Chemistry for Life Science, School of Chemistry and Chemical Engineering, Nanjing University , Nanjing 210093, People's Republic of China.
Anal Chem. 2014 Nov 4;86(21):10877-84. doi: 10.1021/ac503043w. Epub 2014 Oct 20.
A TiO2/CdS:Mn hybrid structure cosensitized with two different sizes of CdTe quantum dots (QDs) was designed to develop a novel and ultrasensitive photoelectrochemical DNA assay. In this protocol, TiO2/CdS:Mn hybrid structure was prepared by successive adsorption and reaction of Cd(2+)/Mn(2+) and S(2-) ions on the surface of TiO2 film and then was employed as matrix for immobilization of hairpin DNA probe, whereas large-sized CdTe-COOH QDs and small-sized CdTe-NH2 QDs as signal amplification elements were successively labeled on the terminal of hairpin DNA probe. The target DNA detection was based upon the photocurrent change originated from conformation change of the hairpin DNA probe after hybridization with target DNA. In the absence of target DNA, the immobilized DNA probe was in the hairpin form and the anchored different sizes of CdTe-COOH and CdTe-NH2 QDs were close to the TiO2/CdS:Mn electrode surface, which led to a very strong photocurrent intensity because of the formation of the cosensitized structure. However, in the presence of target DNA, the hairpin DNA probe hybridized with target DNA and changed into a more rigid, rodlike double helix, which forced the multianchored CdTe QDs away from the TiO2/CdS:Mn electrode surface, resulting in significantly decreased photocurrent intensity because of the vanished cosensitization effect. By using this cosensitization signal amplification strategy, the proposed DNA assay could offer an ultrasensitive and specific detection of DNA down to 27 aM, and it opened up a new promising platform to detect various DNA targets at ultralow levels for early diagnoses of different diseases.
一种 TiO2/CdS:Mn 杂化结构被设计用来与两种不同尺寸的 CdTe 量子点（QDs）共敏化，以开发一种新型超灵敏光电化学 DNA 分析方法。在本方案中，通过 Cd(2+)/Mn(2+)和 S(2-)离子在 TiO2 薄膜表面上的连续吸附和反应制备 TiO2/CdS:Mn 杂化结构，并将其用作发夹 DNA 探针的固定基质，而大尺寸的 CdTe-COOH QDs 和小尺寸的 CdTe-NH2 QDs 则作为信号放大元件被先后标记在发夹 DNA 探针的末端。目标 DNA 的检测是基于杂交后发夹 DNA 探针构象变化引起的光电流变化。在没有目标 DNA 的情况下，固定的 DNA 探针处于发夹状态，锚定的不同尺寸的 CdTe-COOH 和 CdTe-NH2 QDs 接近 TiO2/CdS:Mn 电极表面，由于形成共敏化结构，导致光电流强度非常强。然而，在存在目标 DNA 的情况下，发夹 DNA 探针与目标 DNA 杂交并变成更刚性的棒状双链体，这迫使多锚定的 CdTe QDs 远离 TiO2/CdS:Mn 电极表面，由于共敏化效应的消失，导致光电流强度显著降低。通过使用这种共敏化信号放大策略，所提出的 DNA 分析方法可以实现对 DNA 的超灵敏和特异性检测，检测下限低至 27 aM，为在超低水平下检测各种 DNA 靶标开辟了一个新的有前途的平台，用于不同疾病的早期诊断。
