Scheme 1. Schematic representation of the miRNA-responsive DNA walking nanostructure based on strand displacement cascades. (1) miRNA bound to branch A through toehold-mediated strand displacement, pushing the formed helices between the arm of strand C1 and the track to separate. (2) The released arm of strand C1 walked over to branch B, and the arm of strand C2 from branch B to branch C. (3) C1 and C2 were circulated using T4 DNA ligase. (4) The RCA reactions were performed. (5) The RCA product and the MB hybridized to each other, forming double-stranded DNA. The nicking enzyme catalyzed the multiple cleavage of the molecular beacon, resulting in the generation of a fluorescence signal.
