School of Water Conservancy and Environment, University of Jinan, Jinan 250022, P.R. China.
Analyst. 2018 Nov 19;143(23):5771-5778. doi: 10.1039/c8an01409d.
In the present work, a simple, rapid, isothermal, and ultrasensitive homogeneous electrochemical biosensing platform for target Hg2+ detection was developed on the basis of an exonuclease III (Exo III)-aided target recycling amplification strategy. In the assay, a label-free hairpin probe (HP1) was ingeniously designed, containing a protruding DNA fragment at the 3'-termini as the recognition unit for target Hg2+. Also, the DNA fragment in the loop region and 5'-termini (Helper) could be used when a secondary target analog is introduced, but it is caged in the stem region of HP1 when without such a target. The produced secondary target Helper opened the methylene blue (MB)-labeled hairpin probe (HP2) and triggered the Exo III cleavage process, accompanied with the secondary target recycling. This accordingly resulted in the autonomous reduction of the electroactive material MB on the electrode, inducing a distinct decrease in the electrochemical signal. The current developed homogeneous strategy provides a means for the ultrasensitive electrochemical detection of Hg2+ down to the 227 pM level, with high selectivity. It could be further used as a general autocatalytic and homogeneous strategy toward the detection of a wide spectrum of analytes and may be associated with more analytical techniques.
在本工作中，基于外切酶 III（Exo III）辅助的目标循环放大策略，开发了一种用于目标 Hg2+检测的简单、快速、等温且超灵敏的均相电化学生物传感平台。在该测定中，巧妙设计了一种无标记发夹探针（HP1），其 3'末端含有突出的 DNA 片段作为目标 Hg2+的识别单元。此外，当引入第二个目标类似物时，可以使用环区和 5'末端（Helper）中的 DNA 片段，但在没有此类目标时，它被束缚在 HP1 的茎区。产生的二级目标 Helper 打开了亚甲基蓝（MB）标记的发夹探针（HP2）并触发外切酶 III 切割过程，同时伴随着二级目标循环。这相应导致电极上的电活性物质 MB 自主还原，引起电化学信号明显下降。所开发的均相策略为超灵敏电化学检测 Hg2+提供了一种手段，检测下限低至 227 pM，具有高选择性。它可以进一步用作广泛分析物检测的通用自动催化和均相策略，并可能与更多分析技术相关联。
