Gating of Single Synthetic Nanopores by DNA Molecular Switching

Switchable ion channels that are made of membrane proteins play crucial role in cellular circuits. Thereby synthetic nanofluidic channels attract great interest owing to the novel ion transport properties that are helpful for understanding the biological ion channels and for the promising applications on ultrasensitive molecular detection and separation [1]. Here we report a synthetic nanopore-DNA system where single solid-state nanopores are reversibly gated by switching DNA motors immobilized inside the nanopores. High(on-state) and low(off-state) conductance states are found within the nanopore-DNA system corresponding to the singlestranded and i-motif conformation of the DNA motors. The nanopores were fabricated by the ion-track technique. Chemical etching of the single-ion irradiated foils leads to the formation of conical single nanopore membranes. The large opening (base) was several hundred nanometers, and the narrow opening (tip) was 544 nm. The pH-responsive DNA molecules, which have been extensively studied in the field of nucleic acid nanodevices, were immobilized onto the inner wall of the nanopore by a two-step chemical reaction. The motor DNA molecules (C4-DNA) undergo pH-responsive conformational change between four-stranded i-motif structure (at pH 4.5) and random single-stranded structure (at pH 8.5) (Scheme 1) [2]. The gating performance of the nanopore-DNA system was evaluated by measuring the ionic current across the channel in solution with variant pH.