Micron dimensioned cavity array supported lipid bilayers for the electrochemical investigation of ionophore activity

• Gold cavity arrays support stable, fluidic and solvent free lipid bilayers in presence of ion gradient.
• The pore dimensions make them suited to both electrochemical and microscopy interrogation.
• EIS sensitively reports membrane resistance and capacitance changes on Nigericin or Valinomycin reconstitution.

Microcavity supported lipid bilayers, MSLBs, were applied to an electrochemical investigation of ionophore mediated ion transport. The arrays comprise of a 1 cm2 gold electrode imprinted with an ordered array of uniform spherical-cap pores of 2.8 μm diameter prepared by gold electrodeposition through polystyrene templating spheres. The pores were pre-filled with aqueous buffer prior to Langmuir-Blodgett assembly of a 1,2-dioleoyl-sn-glycero-3-phosphocholine bilayer. Fluorescence lifetime correlation spectroscopy enabled by the micron dimensions of the pores permitted study of lipid diffusion across single apertures, yielding a diffusion coefficient of 12.58 ± 1.28 μm2 s− 1 and anomalous exponent of 1.03 ± 0.02, consistent with Brownian motion. From FLCS, the MSLBs were stable over 3 days and electrochemical impedance spectroscopy of the membrane with and without ionic gradient over experimental windows of 6 h showed excellent stability. Two ionophores were studied at the MSLBs; Valinomycin, a K+ uniporter and Nigericin, a K+/H+ antiporter. Ionophore reconstituted into the DOPC bilayer resulted in a decrease and increase in membrane resistance and capacitance respectively. Significant increases in Valinomycin and Nigericin activity were observed, reflected in large decreases in membrane resistance when K+ was present in the contacting buffer and in the presence of H+ ionic gradient across the membrane respectively.

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