Impedance Analysis and Single-Channel Recordings on Nano-Black Lipid Membranes Based on Porous Alumina

Abstract

Ordered porous alumina substrates with pore diameters of 55 and 280 nm, respectively, were produced and utilized as a support to prepare membranes suspending the pores of the material. Highly ordered porous alumina was prepared by an anodization process followed by dissolution of the remaining aluminum and alumina at the backside of the pores. The dissolution process of Al2O3 at the backside of the pores was monitored by electrical impedance spectroscopy ensuring the desired sieve-like structure of the porous alumina. One side of the porous material with an area of 7 mm2 was coated with a thin gold layer followed by chemisorption of 1,2-dipalmitoyl-sn-glycero-3-phosphothioethanol. The hydrophobic monolayer on top of the upper surface was a prerequisite for the formation of suspending membranes, termed nano-black lipid membranes (nano-BLMs). The formation process, and long-term and mechanical stability of the nano-BLMs were followed by electrical impedance spectroscopy indicating the formation of lipid bilayers with typical specific membrane capacitances of (0.65 ± 0.2) μF/cm2 and membrane resistances of up to 1.6 × 108 Ω cm2. These high membrane resistances allowed for single-channel recordings. Gramicidin as well as alamethicin was successfully inserted into the nano-BLMs exhibiting characteristic conductance states.