Pacific Rim Symposium on Surfaces, Coatings and Interfaces (PacSurf 2014)
    Biomaterial Interfaces Wednesday Sessions
       Session BI-WeM

Paper BI-WeM12
Characterization of Tethered Phospholipid Bilayers by the Electrochemical Impedance Spectroscopy

Wednesday, December 10, 2014, 11:40 am, Room Milo

Session: Biomaterials, Interfaces, and Cells
Presenter: Gintaras Valincius, Vilnius University, Lithuania
Authors: G. Valincius, Vilnius University, Lithuania
M. Mickevicius, Vilnius University, Lithuania
T. Penkauskas, Vilnius University, Lithuania
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We discuss the characterization of tethered phospholipid bilayer membranes (tBLMs) utilizing the electrochemical impedance spectroscopy (EIS). An emphasis is put on applications of tBLMs in protein (peptide)/phospholipid membrane interaction studies. Such interactions modulate the dielectric properties and affect the integrity of phospholipid bilayer. Because of highly asymmetric structure tBLMs exhibit a unique EI response, which cannot be modeled by simple equivalent circuits consisting of capacitors and resistors. We discuss the special functions that describe the characteristic features of the EI spectra. Those analytical functions obtained by solving problem of voltage-current distribution at the interface take into account the structural and dielectric properties of tBLMs. Also, our analysis of the EIS provides the theoretical background for the utility of tBLMs as bioanalytical sensors for the membrane damaging agents, such as pore-forming toxins. We demonstrate that the magnitude and frequency of the negative of the impedance phase minimum, as well as the magnitude of impedance are the parameters indicative of the extent of the membrane damage, and may be used to estimate the defect density in bilayers, as well as the activity of the membrane damaging proteins and peptides. The precision of such estimates is highly dependent on the knowledge of the electric properties of the submembrane electrolyte reservoir separating phospholipid bilayer and solid surface. We present an algorithm, which allows to make estimates of the submembrane specific resistance. Clustering of the defects affects EI response in a unique way, which may be used for the qualitative analysis of the protein membrane interactions.