Ingenious Design of DNA Concatamers and G-Quadruplex Wires Assisted Assembly of Multibranched DNA Nanoarchitectures for Ultrasensitive Biosensing of miRNA.

Facile and efficient assembly of intelligent DNA nano-objects with the ability to exert robust microRNA determination is essential for DNA nanobiotechnology and basic biomedical study. Herein, we present a novel target-triggered DNA assembly pathway for the construction of multibranched DNA nanoarchitectures by the combination of DNA concatamers with G-quadruplex wires. The DNA concatamers acting as the main body structures were assembled by hybridization chain reaction (HCR), while the G-quadruplex wires acting as the branch structures were generated by terminal deoxynucleotidyl transferase (TdT)-promoted polymerization and G-quadruplex units (GUs) based self-assembly. With a copious number of G-quadruplex replicates collected on the electrode surface, the obtained multibranched DNA nanoarchitectures were able to bind with lots of hemin, which further led to a significantly amplified electrochemical sensing signal for ultrasensitive and selective detection of miRNA-21. The detection limit was achieved as low as 0.2 fM with a wide dynamic response ranging from 10 fM to 100 nM, which is much more powerful or at least comparable to most of the reported studies. Furthermore, the electrochemical biosensor offered an excellent specificity, and even the single-base mutation against the perfectly matched target miRNA can be easily distinguished easily. Furthermore, the real biological samples were also desirably analyzed, indicating that the proposed strategy is an ideal platform for the fabrication of versatile DNA nanobiosensors.