A rapid and colorimetric biosensor based on GR-5 DNAzyme and self-replicating catalyzed hairpin assembly for lead detection

摘要

A rapid and colorimetric biosensor for Pb2+ detection has been constructed on the basis of Pb2+-dependent GR-5 DNAzyme and the self-replicating catalyzed hairpin assembly (SRCHA) reaction. In the presence of Pb2+, the phosphodiester bond of the internal RNA base (rA) in GR-5 DNAzyme was cleaved by the enzyme strand and trigger DNA was released. Then the SRCHA reaction was initiated and the H1-H2 complex equipped with single-stranded DNA (ssDNA) sticky ends on both sides was formed. The sequences of the newly formed sticky ends on one side of H1-H2 were the same as that of trigger DNA and then additional CHA reaction cycles were initiated. Meanwhile, the intact G-quadruplex was reunited on the other side of H1-H2 for colorimetric signal readout. By taking advantage of the self-replication of trigger DNA, the response signal in this sensing system was significantly amplified and Pb2+ can be detected in a linear range from 20 to 100 nM with a detection limit of 2.6 nM within 20 min. In addition, this method can be applied to the reliable monitoring of spiked Pb2+ in environmental water and serum samples with satisfying results, providing a potential method for on-site and real-time detection of Pb2+ for environmental protection and related disease prevention.