In this work, an ultrasensitive method for trace protein detection based on fluorescent carbon nanodots and hybridization chain reaction (HCR) is designed. Generally, the synthesized bright carbon nanodots are conjugated with two hairpin‐structured DNA probes, respectively, which act as subsequent HCR fuel strands. Since single‐stranded parts of DNA probes could be easily absorbed on graphene oxide (GO) nanosheets, fluorescence emission of carbon nanodots is effectively quenched via fluorescence resonance energy transfer. However, in the presence of target protein, the aptamer sequence in another hairpin‐structured DNA probe specially interacts with target and the hairpin is opened. A single‐stranded region is thus exposed, which initiates HCR by coupling with the DNA fuel strands on carbon nanodots. The formed HCR product displays a rigid, long double‐stranded structure, which facilitates the release of carbon nanodots from GO surface. As a result, fluorescence of carbon nanodots is recovered and initial concentration of target protein can be estimated. This protein detection method shows a favorable linear response with a low limit of detection (2.3 fg mL⁻¹). Furthermore, it is highly selective and capable of detecting target in biological fluids like serum samples, which demonstrates the promising applications of this method.

中文翻译：

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基于碳纳米点和杂交链反应的痕量蛋白质荧光开启分析

在这项工作中，设计了一种基于荧光碳纳米点和杂交链反应（HCR）的痕量蛋白质检测的超灵敏方法。通常，合成的亮碳纳米点分别与两个发夹结构的DNA探针缀合，它们充当后续的HCR燃料链。由于DNA探针的单链部分可以很容易地吸附在氧化石墨烯（GO）纳米片上，因此碳纳米点的荧光发射可通过荧光共振能量转移得到有效淬灭。但是，在存在目标蛋白的情况下，另一种由发夹结构构建的DNA探针中的适体序列会与靶标特别相互作用，并且发夹会被打开。因此暴露出一个单链区域，该区域通过与碳纳米点上的DNA燃料链偶联来启动HCR。成型的HCR产品显示出刚性，长双链结构，有利于碳纳米点从GO表面释放。结果，回收了碳纳米点的荧光，并且可以估计靶蛋白的初始浓度。这种蛋白质检测方法显示出良好的线性响应，检测限低（2.3 fg mL^-1）。此外，它具有很高的选择性，并且能够检测生物液体（如血清样品）中的靶标，这证明了该方法的应用前景。