Magnetic DNAzyme nanomachine fluorescent biosensor for Pb(Ⅱ) detection

The lead ion (Pb2+) is harmful to human. Detecting low content of Pb2+ in the environment requires high sensitive and specific detection technology. In this study, we developed a magnetic DNAzyme nanomachine fluorescent biosensor for rapid and ultra-sensitive detection of Pb2+. We focused on using bovine serum albumin (BSA) as a bridge to connect magnetic beads and DNAzyme in the magnetic nanomachine, aiming to improve the detection sensitivity. In the presence of Pb2+, the enzyme cleavage activity was activated, leading to the substrate chains cleaved and released. Meanwhile, Pb2+ participated in the cyclic process of recognition and release, which contributed to signal amplification. The cleavage products and stem-loop chains were assembled and amplified using the double primer realtime fluorescence quantitative reaction (qPCR) method. By applying such triple amplifications of the signal, Pb2+ was quantitatively detected by measuring the change in the Ct value (ΔCt) before and after cleavage of the DNAzyme. Under optimized assay conditions, a linear relationship ranging from 2 nM to 150 nM was observed with a limit of detection (LOD) of 3.7 nM for Pb2+. In conclusion, our approach offers a potentially useful method for simple, rapid, and sensitive Pb2+ detection.