A Reagentless Signal-On Architecture for Electronic, Aptamer-Based Sensors via Target-Induced Strand Displacement

Thrombin binding stabilizes the alternative G-quadruplex conformation of the aptamer, liberating the methylene blue (MB)-tagged oligonucleotide to produce a flexible, single-stranded DNA element. This allows the MB tag to collide with the gold electrode surface, producing a readily detectable Faradaic current at thrombin concentrations as low as ∼3 nM.