Pore-Spanning PPy(DBS) as a Voltage-Gated Synthetic Membrane Ion Channel

The transport of monovalent cations across a suspended PPy(DBS) polymer membrane in an aqueous solution as a function of its redox state is investigated. Maximum ion transport is found to occur when PPy(DBS) is in the reduced state, and minimum transport in the oxidized state. No deviation in the dynamics of ion transport based on the direction of the applied electrical field is observed. Additionally, it is found that ion transport rates linearly increased proportional to the state of reduction until a steady state is reached when the polymer is fully reduced. Therefore controlled, bidirectional ion transport is for the first time demonstrated. The effect of aqueous Li⁺ concentration on ion transport in the fully reduced state of the polymer is studied. It is found that ion transport concentration dependence follows Michaelis-Menten kinetics (which models protein reaction rates, such as those forming ion channels in a cell membrane) with an r² value of 0.99. For the given PPy(DBS) polymer charge density and applied potential across the membrane, the maximum possible ion transport rate per channel is found to be 738 ions per second and the Michaelis constant, representing the concentration at which half the maximum ion transport rate occurs, is 619.5mM.