pH Dependence of γ-Aminobutyric Acid Iontronic Transport.

The organic electronic ion pump (OEIP) has been developed as an "iontronic" tool for delivery of biological signaling compounds. OEIPs rely on electrophoretically "pumping" charged compounds, either at neutral or shifted pH, through an ion-selective channel. Significant shifts in pH lead to an abundance of H+ or OH-, which are delivered along with the intended substance. While this method has been used to transport various neurotransmitters, the role of pH has not been explored. Here we present an investigation of the role of pH on OEIP transport efficiency using the neurotransmitter γ-aminobutyric acid (GABA) as the model cationic delivery substance. GABA transport is evaluated at various pHs using electrical and chemical characterization and compared to molecular dynamics simulations, all of which agree that pH 3 is ideal for GABA transport. These results demonstrate a useful method for optimizing transport of other substances and thus broadening OEIP applications.