Hydrophobic Gating in Synthetic Nanopores

Abstract

In nature, nanopores play a critical role in a number of vital biological functions and understanding this role is just as critical. These pores can be ion selective based on their size and/or surface charge, but further functionality is achieved by modulating, or gating, their conductance state. The conductivity of a particular nanochannel can be controlled in a number of ways, including mechanically, chemically and electrically. By studying these phenomena in model systems, we may be able to take large steps towards understanding the underlying fundamental physics phenomena behind these mechanisms. Here, we present what we believe to be the first study to show the gating of a synthetic channel based on its hydrophobicity, which has been observed to be a natural gating mechanism in mechanosensitive channels.Using nanopores prepared in polyethylene terephthalate (PET) by the track-etching technique, we show that it is possible to decorate the pore surface with hydrophobic chemical groups and that these significantly alter the properties of the pore. Prior to modification, aqueous electrolytic solutions are able to conduct readily through the pore, but afterwards, the pore demonstrates closed and open states. This behavior is also observed to be voltage dependent. Increasing voltage increases the probability of the pore to be in the open states. There is also a voltage range where the pore does not conduct at all. The hydrophobic gating was studied as a function of pore diameter and charge of the residual groups.