Giant Catalytic DNA Particles for Simple and Intuitive Detection of Pb²⁺

DNAzymes have been extensively studied as biosensors because of their unique functionality of cleaving substrate in the presence of metal ion cofactors. However, there are only a few reports on visual detection using gold nanoparticles. Here, we synthesized the DNAzyme microparticle (DzMP) (~1 μm) via rolling circle amplification for detection of Pb²⁺ without the help of other materials. Then, the substrate strands were labeled with two different fluorophores (6-carboxyfluorescein and Cy5) to visualize the DzMPs and to monitor the separation of substrate strands. Because of their large size, the decline in the number of fluorescent particles in the presence of Pb²⁺ could be successfully demonstrated by a fluorescence microscopy, presenting a new platform for heavy metal detection.