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    Electrochemically Triggered Release of Reagent to the Proximal Leaflet of a Microcavity Supported Lipid Bilayer

    Year: 2017

    Journal: Langmuir, Volume 33, JUL 11, page 6691–6700

    Authors: Basit, H.; Maher, S.; Forster, R. J.; Keyes, T. E.

    Organizations: Science Foundation Ireland [10/CE/B1821, 14/IA/2488]; National Biophotonics and Imaging Platform, Ireland - Irish Programme for Research in Third Level Institutions, Cycle 4, Ireland's EU Structural Funds Programmes

    A novel and versatile approach to electrichemically triggering the release of a reagent, beta-cydodextrin (beta-CD), selectively to the proximal leaflet of a supported lipid bilayer is described. Selective delivery is achieved by creating a spanning lipid bilayer across a microcavity array and exploiting the irreversible redox disassembly of the host guest complex formed between thiolated ferrocene (Fc) and beta-cyclodextrin (beta-CD) in the presence of chloride. Self-assembled mono layers of the ferrocene alkanethiols were formed regioselectively on the interior surface of highly ordered 2.8 mu m cavities while the exterior top surface of the array was blocked with a monolayer of rnercaptoethanol. The Fc monolayers were complexed with beta-CD or beta-CD-conjugated to streptavidin (beta-CD-SA). Phospholipid bilayers were then assembled across the array via combined Langmuir Blodgett/vesicle fusion leading to a spanning bilayer suspended across the aqueous filled microcavities. Upon application of a positive potential, ferrocene is oxidized to ferrocinium cation, disrupting the inclusion complex and leading to the release of the beta-CD into the microcavity solution where it diffuses to the lower leaflet of the suspended bilayer. Disassembly of the supramolecular complex within the cavities and binding of the fi-CD-SA to a biotinylated bilayer was followed by voltammetry and impedance spectroscopy where it caused a large increase in membrane resistance. For unmodified beta-CD, the extraction of cholesterol from a cholesterol containing bilayer was evident in a decrease in the bilayer resistance. For the first time, this direct approach to targeted delivery "of a reagent to the proximal layer of a lipid bilayer offers the potential to build models of bidirectional signaling (inside-outvs outside-in) in cell membrane model systems.
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