The reduced graphene oxide (rGO) could strongly adsorb and quench the fluorescence of dye-labeled single-stranded DNA (ssDNA); thus, it is widely applied in fluorescent sensors. However, these sensors may suffer from a limited sensitivity due to the low fluorescence recovery when adding the complementary DNA (cDNA) sequence. In this work, the powerful DNA branched junctions were constructed to improve the fluorescence recovery of FAM-labeled probe on rGO. In the presence of target Pb2+, the ribonucleotide (rA) in the substrate was cleaved specifically and the catalytic hairpin assembly of three metastable hairpins was further initiated, accompanied by the formation of DNA branched junctions. Then, the liberated Pb2+ could be recyclable. Impressively, the DNA branched junctions not only hybridize with the FAM-labeled probes with a high efficiency, but also are significantly undesirable for the rGO. Thus, a high fluorescence recovery of FAM-labeled probe on rGO was expected. The integration of the high fluorescence recovery and dual-cycle signal amplification endows the sensing strategy with a good performance for Pb2+ detection, including low detection limit (0.17 nM), good selectivity, and satisfactory practical applicability. The proposed DNA branched junctions offer a novel avenue to improve the fluorescence recovery of the dye-labeled probes on rGO for biological analysis.

中文翻译：

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DNA分支连接在rGO上诱导FAM标记的探针检测Pb2的荧光恢复增强。

还原的氧化石墨烯（rGO）可以强烈吸附并淬灭染料标记的单链DNA（ssDNA）的荧光；因此，它被广泛应用于荧光传感器。但是，由于添加互补DNA（cDNA）序列时荧光恢复率低，这些传感器的灵敏度可能会受到限制。在这项工作中，强大的DNA分支连接被构建以提高rGO上FAM标记探针的荧光回收率。在存在目标Pb2 +的情况下，底物中的核糖核苷酸（rA）被特异性裂解，并且三个亚稳态发夹的催化发夹组装进一步启动，并伴随着DNA分支结的形成。然后，释放的Pb2 +可以回收利用。令人印象深刻的是，DNA分支连接不仅可以与FAM标记的探针高效杂交，但对于rGO来说也是非常不希望的。因此，期望rGO上的FAM标记探针具有高荧光回收率。高荧光回收率和双周期信号放大相结合，使传感策略具有良好的Pb2 +检测性能，包括低检测限（0.17 nM），良好的选择性和令人满意的实用性。拟议的DNA分支连接提供了一种新途径，可以改善rGO上染料标记探针的荧光回收率，以进行生物学分析。17 nM），良好的选择性和令人满意的实际适用性。拟议的DNA分支连接提供了一种新途径，可以改善rGO上染料标记探针的荧光回收率，以进行生物学分析。17 nM），良好的选择性和令人满意的实际适用性。拟议的DNA分支连接提供了一种新途径，可以改善rGO上染料标记探针的荧光回收率，以进行生物学分析。