Key Laboratory of Applied Surface and Colloid Chemistry, Ministry of Education, School of Chemistry and Chemical Engineering, Shaanxi Normal University, Xi'an 710062, China.
Anal Chim Acta. 2013 Oct 17;799:36-43. doi: 10.1016/j.aca.2013.09.024. Epub 2013 Sep 14.
A signal-on impedimetric electrochemical DNA (E-DNA) sensor using gold nanoparticles (AuNPs) as tag was developed for highly sensitive detection of DNA hybridization. A probe ssDNA (PDNA) was immobilized by forming an amide between the -NH2 moiety at the 5'-terminus of PDNA and the -COOH group at self-assembled 11-mercaptoundecanoic acid on a gold electrode. Subsequently, AuNPs were attached to the -SH moiety at the 3'-terminus of the immobilized PDNA by S-Au interaction, and then functionalized with -OH by immersing the electrode in dithiothreitol solution. In the absence of the target DNA, the flexible single-stranded PDNA supports efficient contact between AuNP tag and electrode, ensuring a low electron transfer resistance (Ret) of the E-DNA sensor using the Fe(CN)6 redox probe. Upon hybridization, a rigid probe-target duplex is formed, which pushes the AuNP tag away from the electrode and increases the distance between AuNP tag and the electrode, thereby increasing the Ret of the E-DNA sensor. Based on hybridization-induced conformational changes, the E-DNA sensor shows an increased Ret response when the target DNA concentration is increased from 5 fM to 500 pM. Furthermore, the E-DNA sensor showed differentiation abilities for single-base mismatch.
一种基于金纳米粒子（AuNPs）作为标记的信号增强型电化学 DNA（E-DNA）传感器被开发用于高灵敏度的 DNA 杂交检测。探针 ssDNA（PDNA）通过在 PDNA 的 5'末端的-NH2 部分和自组装的 11-巯基十一酸上的-COOH 基团之间形成酰胺键而被固定在金电极上。随后，AuNPs 通过 S-Au 相互作用附着在固定化 PDNA 的 3'末端的-SH 部分上，然后通过将电极浸入二硫苏糖醇溶液中使其功能化 -OH。在没有靶 DNA 的情况下，柔性单链 PDNA 支持 AuNP 标记与电极之间的有效接触，确保使用 Fe(CN)6 氧化还原探针的 E-DNA 传感器具有低的电子转移电阻（Ret）。杂交后，形成刚性的探针-靶双链体，将 AuNP 标记物从电极推开，并增加 AuNP 标记物与电极之间的距离，从而增加 E-DNA 传感器的 Ret。基于杂交诱导的构象变化，当靶 DNA 浓度从 5 fM 增加到 500 pM 时，E-DNA 传感器的 Ret 响应增加。此外，该 E-DNA 传感器还表现出对单碱基错配的区分能力。
