Sensitive electrochemical detection of microRNA based on DNA walkers and hyperbranched HCR-DNAzyme cascade signal amplification strategy

The designable and configurable DNA nanostructures with various biological functions have been widely applied in biosensors especially for detection of nucleic acid. In this work, a cascade signal amplification strategy based on DNAzyme-driven 3D DNA walkers combined with hyperbranched HCR and DNAzyme catalyzation were applied for sensitive electrochemical detection of microRNA-141. First, the Mg2+-dependent cleavage of DNAzyme trigger the autonomous DNA walking process, inducing the generation of mediate strand output, thereby leading the construction of hyperbranched HCR and subsequently providing more embedding sites for electroactive molecules. Meanwhile, the G-quadruplex domains are introduced by the terminal of DNA strand in constructing hyperbranched nanostructure. Finally, the formed hemin/G-quadruplex DNAzyme (a horseradish peroxidase-mimicking DNAzyme) could catalyze the decomposition of H2O2, greatly increasing the intensity of electrochemical signal. Combined with the DNAzyme-driven 3D DNA walkers, hyperbranched HCR and DNAzyme catalyst assisted amplification strategies, the electrochemical biosensor showed a wide linear range for the detection of microRNA-141 with favorable sensitivity and selectivity. The performance of this biosensor in different cell lysates were evaluated, which showed great potential in assay of microRNAs at low expression levels in complex samples.