The localized hairpin-DNA cascade reaction exhibited some fascinating merits over the traditional hairpin-DNA hybridization reaction, such as the reduced reaction time and enhanced hybridization efficiency. However, the reported localized hairpin-DNA cascade reaction usually needed the participation of expensive proteases, which limited their application. This work developed a magnetic nanobeads (MBs)-assisted highly-ordered enzyme-free localized DNA cascade reaction (HELDCR) to achieve highly efficient signal amplification. With the help of magnetically separable MBs, a novel fluorescent sensor was constructed for the ultrasensitive detection of Pb²⁺. In the presence of the target Pb²⁺, the DNAzyme chain was activated and the substrate chain was cleaved. The released DNAzyme chain could trigger the HELDCR and open the highly-ordered assembled hairpin structures (HAHs) on MBs, which promoted substantial fluorophores FAM and quenchers BHQ mutually close. The proximity of FAM and BHQ caused signal quenching, thus achieving a satisfactory performance for detecting Pb²⁺ with a low detection limit of 3.0 pM. The synergistic effect of the HELDCR and MBs provided an attractive and sensitive fluorescent platform for biological analysis in the homogeneous environment.

与传统的发夹DNA杂交反应相比，发夹DNA级联反应具有一定的吸引力，缩短了反应时间，提高了杂交效率。然而，所报道的局部发夹-DNA级联反应通常需要昂贵的蛋白酶的参与，这限制了它们的应用。这项工作开发了磁性纳米珠（MBs）辅助的高度有序的无酶局部DNA级联反应（HELDCR），以实现高效的信号放大。借助可磁分离的MB，构建了一种新型的荧光传感器，用于超灵敏地检测Pb ²⁺。在目标Pb ²⁺存在的情况下，DNAzyme链被激活，底物链被切割。释放的脱氧核糖核酸酶链可能触发HELDCR并打开MBs上高度有序的组装发夹结构（HAH），从而促进大量的荧光团FAM和淬灭剂BHQ相互靠近。FAM和BHQ的接近引起信号猝灭，因此以3.0 pM的低检测限实现了令人满意的检测Pb ^2+的性能。HELDCR和MB的协同作用为均匀环境中的生物分析提供了一个有吸引力且灵敏的荧光平台。