Ultrasensitive detection of lead ion based on target induced assembly of DNAzyme modified gold nanoparticle and graphene oxide

In this paper, we report a novel colorimetric strategy for the detection of small molecules by using Pb(2+) ion as an example. In this strategy, DNAzyme duplex modified gold nanoparticles (GNPs) are designed to be unable to interact with graphene oxide (GO). However, in the presence of Pb(2+), the substrate strand of the DNAzyme is cleaved at its cleavage site, resulting in the disassembly of the DNAzyme duplex modified GNPs into three parts, i.e., the 3'- and 5'-fragments of substrate strand and the DNAzyme strand modified GNPs. By taking advantage of the efficient cross-linking effect of ssDNA-GNPs to GO, colorimetric sensor for the detection of the metal ion can be fabricated with a detection limit of 100 pM, which is much lower than the previous reports. This colorimetric method has also been used for the determination of Pb(2+) in the tap water of the local city and the water from a reservoir with satisfactory results, so it may have potential applications in the future.