A ligand-gated ion-channel mimetic nanopore membrane with an on-board transmembrane microbattery.

We have been investigating synthetic nanopore membranes that mimic the function of ligand-gated ion channels. We showed previously that the transmembrane ion current in a hydrophobic alumina nanopore membrane can be switched from an "off" state to an "on" state by exposure of the membrane to hydrophobic ionic surfactants. In these prior experiments, external electrodes and an external power supply were used to drive the ion current when the membrane was in its "on" state. In biological channels there are no electrodes, and the ion current is driven by an electrochemical potential difference across the cell membrane. In this article we mimic this function of the ligand-gated ion channel by applying a porous battery cathode film to one face of the hydrophobic alumina membrane and a porous battery anode film to the other face. Hence, in analogy to the naturally occurring channel case, we have a membrane with a built in electrochemical potential difference across the membrane. We show here that in the absence of the ligand (again, a hydrophobic ionic surfactant), the membrane is in its "off" state, and the electrochemical potential difference cannot be utilized to drive a transmembrane ion current. In contrast, when the ligand is detected, the membrane switches to its "on" state and the transmembrane battery discharges, producing a corresponding transmembrane ion current.