A highly sensitive DNAzyme-based SERS biosensor for quantitative detection of lead ions in human serum.

Lead ions (Pb), one form of the toxic heavy metal, have drawn significant attention due to their harmful effects on human health and the environment. Although many analytical techniques have been developed over the past few decades, the development of a sensitive, selective, and rapid method to detect Pb remains a challenge. In this work, we developed a sensitive surface-enhanced Raman scattering (SERS) biosensor for highly sensitive detection of Pb by using DNAzyme-modified FeO@Au@Ag nanoparticles (FeO@Au@Ag NPs). Firstly, the thiolated 5'-Cy3 DNA probe was modified on the surface of FeO@Au@Ag NPs, which hybridized with the Pb-specific DNAzyme to form a SERS biosensor, and the Cy3 labels were used to detect Pb. In the presence of Pb, the DNAzyme cleaves the Cy3-labeled DNA probe, leading to the release of Cy3-labeled DNA probe from the FeO@Au@Ag NPs. Therefore, the Raman intensity of the Cy3 labels decreases. The proposed biosensor exhibited excellent linearity in the range from 0.01 to 1.0 nM, with a limit of detection for Pb of 5 pM. It features superior selectivity to Pb over other interfering metal ions and good application in the determination of Pb in tap water and human serum samples. The SERS biosensor provides a novel' simple and sensitive method for detection of Pb and sheds new light on the design and synthesis of analogous SERS biosensors for the detection of other heavy metal ions.