Biomimetic, Voltage-Sensitive Nanopores with Local Control over Pore Position, Size and Surface Chemistry

Abstract

Excitable ion channels play an essential role in biology by regulating ion transport across cell membranes. A key characteristic of these nanoscale pores is the ability to respond to environmental stimuli such as changes in the local membrane voltage or ion concentration. The replication of this behavior in synthetic nanopore platforms has the potential to enable new responsive materials useful in applications such as biomimetic componentry, drug delivery and filtration technologies. While voltage gating has been demonstrated before in synthetic nanopores, previous fabrication methods make it difficult to incorporate such pores into more complex systems due to lack of control over key attributes such as pore location. Here, we present the fabrication of a voltage and ion concentration responsive nanochannel with local control over the pore location, size, shape and surface chemistry. This is achieved using focused ion beam (FIB) to nanomachine a pore in a SiNx membrane followed by ion-beam-controlled deposition of SiOx around the pore entrance. Chemistry selective for SiOx is then used to graft single stranded DNA (ssDNA) only to the regions where the local deposition was performed. Recorded voltage-sensitive transport is complex and dictated by both the charge and conformational changes of ssDNA chains in confinement. For small enough pore diameters, interplay between the applied voltage and local ion concentrations at the pore opening results in three pore states, each with different conductance behavior. Hysteresis was also observed, which is attributed to steric barriers to ssDNA conformational changes in a confined space. This successful demonstration of biomimetic nanopores with local control of multiple chemical and geometric properties is an important step towards the integration of nanopore technology into more complex multi-component systems.