DNA-Modified Polymer Pores Allow pH- and Voltage-Gated Control of Channel Flux

Abstract

Biological channels embedded in cell membranes regulate ionic transport by responding to external stimuli such as pH, voltage, and molecular binding. Mimicking the gating properties of these biological structures would be instrumental in the preparation of smart membranes used in biosensing, drug delivery, and ionic circuit construction. Here we present a new concept for building synthetic nanopores that can simultaneously respond to pH and transmembrane potential changes. DNA oligomers containing protonatable A and C bases are attached at the narrow opening of an asymmetric nanopore. Lowering the pH to 5.5 causes the positively charged DNA molecules to bind to other strands with negative backbones, thereby creating an electrostatic mesh that closes the pore to unprecedentedly high resistances of several tens of gigaohms. At neutral pH values, voltage switching causes the isolated DNA strands to undergo nanomechanical movement, as seen by a reversible current modulation. We provide evidence that the pH-dependent reversible closing mechanism is robust and applicable for nanopores with opening diameters of up to 14 nm. The concept of creating an electrostatic mesh may also be applied to different organic polymers.

Halide-Gated Molecular Release from Nanoporous Gold Thin Films

“…While gated-release is of significant interest for stimuli-responsive platforms, [54][55][56][57][58][59] the sensitivity of molecular release from the np-Au network to halides constitutes a challenge for using np-Au in physiological conditions due to the halide abundance. 40,41 Informed by the results revealing halide-gold interaction as the main driver of the release process, we hypothesized that SAMs onto the gold ligaments might dampen the degree of halide-surface interaction, therefore modulating the release processes.…”

Photo-switchable two-dimensional nanofluidic ionic diodes

“…1,2 Recent advances in chemistry, materials science, and nanotechnology elicit unprecedented interest in constructing ion-channel-mimetic nanofluidic systems that show adaptive responsiveness to environmental stimuli. 3,4 So far, one dimensional (1D) smart nanofluidic devices in response to pH, 5–7 temperature, 8,9 specific ionic or molecular targets, 10–13 and light irradiation 14,15 have been intensively studied. For example, Wang et al report a photochemical switch in spiropyran modified glass nanopores that selectively transports charged redox species.…”

Coordination of the electrical and optical signals revealing nanochannels with an ‘onion-like’ gating mechanism and its sensing application

“…For example, it is possible to observe a current blockade even if the molecules are at the channel tip rather than in the channel lumen. 19,20 In addition, the ionic current provides temporal information instead of spatial information on the process of gating, which makes it difficult to investigate the mechanism of gating. To address these limitations, the incorporation of additional measurements that supplement the electrical measurements to validate the envisaged gating process through the ion channels is indispensable.…”