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    Resonance-Mode Electrochemical Impedance Measurements of Silicon Dioxide Supported Lipid Bilayer Formation and Ion Channel Mediated Charge Transport

    Year: 2011

    Journal: Anal. Chem., 2011, 83 (20), pp 7800–7806, 20111207

    Authors: Lundgren A.†, Hedlund J.‡, Andersson O.‡, Brändén M.‡§, Kunze A.§, Elwing H.†, Höök F.*§

    Last authors: Fredrik Höök

    Organizations: Department of Cell and Molecular Biology, University of Gothenburg, SE-405 30 Gothenburg, Sweden Stena Center 1B, Layerlab AB, SE-41292 Gothenburg, Sweden Department of Applied Physics, Chalmers University of Technology, SE-412 96 Gothenburg, Sweden

    Country: Sweden, Sverige

    A single-chip electrochemical method based on impedance measurements in resonance mode has been employed to study lipid monolayer and bilayer formation on hydrophobic alkanethiolate and SiO2 substrates, respectively. The processes were monitored by temporally resolving changes in interfacial capacitance and resistance, revealing information about the rate of formation, coverage, and defect density (quality) of the layers at saturation. The resonance-based impedance measurements were shown to reveal significant differences in the layer formation process of bilayers made from (i) positively charged lipid 1-palmitoyl-2-oleoyl-sn-glycero-3-ethylphosphocholine (POEPC), (ii) neutral lipid 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) on SiO2, and (iii) monolayers made from POEPC on hydrophobic alkanethiolate substrates. The observed responses were represented with an equivalent circuit, suggesting that the differences primarily originate from the presence of a conductive aqueous layer between the lipid bilayers and the SiO2. In addition, by adding the ion channel gramicidin D to bilayers supported on SiO2, channel-mediated charge transport could be measured with high sensitivity (resolution around 1 pA).