A novel magnetic beads-assisted highly-ordered enzyme-free localized DNA cascade reaction for the fluorescence detection of Pb~(2+)

摘要

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 Pb~(2+). In the presence of the target Pb~(2+), 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 Pb~(2+) 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.