Herein, we report an optical sensing platform for mercury ions (Hg²⁺) in water based on the integration of Hg²⁺-mediated thymine-thymine (T-T) stabilization, a biotinylated stem-loop DNA probe, and a streptavidin-modified retroreflective Janus particle (SA-RJP). Two oligonucleotide probes, including a stem-loop DNA probe and an assistant DNA probe, were utilized. In the absence of Hg²⁺, the assistant DNA probe does not hybridize with the stem-loop probe due to their T-T mismatch, so the surface-immobilized stem-loop DNA probe remains a closed hairpin structure. In the presence of Hg²⁺, the DNA forms a double-stranded structure with the loop region via Hg²⁺-mediated T-T stabilization. This DNA hybridization induces stretching of the stem-loop DNA probe, exposing biotin. To translate these Hg²⁺-mediated structural changes in DNA probe into measurable signal, SA-RJP, an optical signaling label, is applied to recognize the exposed biotin. The number of biospecifically bound SA-RJPs is proportional to the concentration of Hg²⁺, so that the concentration of Hg²⁺ can be quantitatively analyzed by counting the number of RJPs. Using the system, a highly selective and sensitive measurement of Hg²⁺ was accomplished with a limit of detection of 0.027 nM. Considering the simplified optical instrumentation required for retroreflection-based RJP counting, RJP-assisted Hg²⁺ measurement can be accomplished in a much easier and inexpensive manner. Moreover, the detection of Hg²⁺ in real drinking water samples including tap and commercial bottled water was successfully carried out.

在此，我们报告了一个基于Hg ²⁺介导的胸腺嘧啶-胸腺嘧啶（TT）稳定化，生物素化茎环DNA探针和链霉亲和素修饰的逆向反射的集成的水中汞离子（Hg ²⁺）的光学传感平台。Janus粒子（SA-RJP）。使用了两个寡核苷酸探针，包括茎环DNA探针和辅助DNA探针。在没有Hg ²⁺的情况下，辅助DNA探针由于TT不匹配而不会与茎环探针杂交，因此表面固定的茎环DNA探针保持闭合的发夹结构。在存在Hg ²⁺的情况下，DNA通过Hg ²⁺与环区形成双链结构-介导的TT稳定化。这种DNA杂交诱导了茎环DNA探针的拉伸，从而暴露了生物素。为了将这些Hg ²⁺介导的DNA探针结构变化转化为可测量的信号，应用SA-RJP（一种光学信号标记）来识别暴露的生物素。生物特异性结合的SA-RJPs的数量与Hg ²⁺的浓度成正比，因此可以通过计算RJPs的数量来定量分析Hg ²⁺的浓度。使用该系统，可以以0.027 nM的检出限实现对Hg ²⁺的高度选择性和灵敏的测量。考虑到基于回反射的RJP计数所需的简化光学仪器，RJP辅助的Hg ²⁺可以以更容易和便宜的方式完成测量。此外，成功进行了包括自来水和商业瓶装水在内的实际饮用水样品中Hg ²⁺的检测。