A novelty aptasensor for ultrasensitive detection of Hg2+ is developed, exploiting the combination of plasmonic properties of gold nanoparticles (AuNPs) and exonuclease III (Exo III)-assisted target recycling for signal amplification. In the presence of Hg2+, a DNA duplex can be formed due to the strong coordination of Hg2+ and T bases of single-stranded DNA (ssDNA) probe. Exo III digests the DNA duplex from the 3' to 5' direction, resulting in the releasing of Hg2+. Then, the released Hg2+ binds with another ssDNA probe through T-Hg2+-T coordination. After Exo III-assisted Hg2+ cycles, numerous ssDNA probes are exhausted, which promotes poly(diallyldimethylammonium chloride) (PDDA)-induced AuNP aggregation, leading to an obvious color change and aggregation-induced plasmon red shift of AuNPs (from 520 to 610 nm). Therefore, this biosensor is ultrasensitive, which is applicable to the detection of trace level of Hg2+ with a linear range from 5 pM to 0.6 nM and an ultralow detection limit of 0.2 pM. Furthermore, it enables visual detection of Hg2+ as low as 50 pM by the naked eye. More importantly, the assay can be applied to the reliable determination of spiked Hg2+ in sea water samples with good recovery.

中文翻译：

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基于 T-Hg2+-T 构型和目标回收放大的 Hg2+ 检测超灵敏比色策略。

开发了一种用于 Hg2+ 超灵敏检测的新型适体传感器，利用金纳米粒子 (AuNPs) 和核酸外切酶 III (Exo III) 辅助目标回收的等离子体特性的组合进行信号放大。在 Hg2+ 存在下，由于 Hg2+ 和单链 DNA (ssDNA) 探针的 T 碱基的强配位，可以形成 DNA 双链体。Exo III 从 3' 到 5' 方向消化 DNA 双链体，导致 Hg2+ 的释放。然后，释放的 Hg2+ 通过 T-Hg2+-T 协调与另一个 ssDNA 探针结合。Exo III 辅助的 Hg2+ 循环后，大量 ssDNA 探针被耗尽，这促进了聚（二烯丙基二甲基氯化铵）（PDDA）诱导的 AuNP 聚集，导致 AuNPs 的明显颜色变化和聚集诱导的等离子体红移（从 520 到 610 nm ）。所以，该生物传感器超灵敏，适用于痕量Hg2+的检测，线性范围为5 pM至0.6 nM，超低检测限为0.2 pM。此外，它还可以通过肉眼对低至 50 pM 的 Hg2+ 进行视觉检测。更重要的是，该测定可用于可靠测定海水样品中的加标 Hg2+，回收率良好。