Solid-state nanopore based biomimetic voltage gated ion channels

Voltage gating is essential to the computational ability of neurons. We show this effect can be mimicked in a solid-state nanopore by functionalizing the pore interior with a redox active molecule. We study the integration of an active biological molecule-a quinone-into a solid state nanopore, and its subsequent induced voltage gating. We show that the voltage gating effect mimics biological gating systems in its classic sigmoidal voltage response, unlike previous synthetic voltage gating systems. Initially, the quinone undergoes a reduction due to radicals in the bulk solution, and is converted to the hydroquinone state. Upon deprontonation the hydroquinone then acts as a charged nanomechanical arm, which opens the channel under the applied potential. We establish that the quinone gains a single net charge when the pH inside of the nanopore reaches its pKa value, and explore factors that influence the net pH in the middle of the pore. Using a combination of theory, experiment and simulation, we conclude that concentration polarization and a shift of the pH inside of the channel is the main cause of this gating effect.