A novel fluorescent biosensor for detection of Pb²⁺ based on Pb²⁺-specific DNAzyme and carbon dots prepared from watermelon rind

A novel fluorescent biosensor was constructed to detect Pb2+. Multifunctional magnetic beads modified with substrate sequence and Pb2+-specific DNAzyme were employed as recognition probes. The fluorescence of carbon dots synthesized from watermelon rind (W-CDs) was quenched by hemin. Hemin/W-CDs were employed as fluorescent signals. The presence of Pb2+ could target-trigger the biosensor, and generated G-quadruplex which could restore the fluorescence of hemin/W-CDs. The fluorescence change of the biosensor depended on Pb2+ concentration from 1 to 20 nM.