A novel magnetic beads-assisted highly-ordered enzyme-free localized DNA cascade reaction for the fluorescence detection of Pb2+

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.

Automated summary

The study developed a novel fluorescent sensor for ultrasensitive detection of Pb2+ using the HELDCR method, achieving a low detection limit and efficient signal amplification. This approach provided an attractive and sensitive fluorescent platform for biological analysis in a homogeneous environment.