291391 Impedance Analysis of Endothelial Cells in Development of an Orbital Shear Platform

Tuesday, October 30, 2012
Hall B (Convention Center )
Mark Gruenthal, Mechanical Engineering, University of Louisville , Louisville, KY, Vanessa Velasco, University of Louisville, Louisville, KY, R. Eric Berson, Chemical Engineering, University of Louisville, Louisville, KY, Robert Keynton, Department of Bioengineering, University of Louisville, Louisville, KY and Stuart J. Williams, Mechanical Engineering, University of Louisville, Louisville, KY

Impedance analysis of adherent cells on top of an electrode can reveal information about cell morphology, monolayer permeability, and other physiological parameters.  This data provides insights into the structure and functionality of the endothelium in real-time.  Because the cell monolayer is subjected to wall shear stresses that oscillate due to the pulsatile flow of the cardiovascular system it is necessary to investigate the behavior of endothelial cells under conditions that simulate the environment in vivo.   The aim of this study is to develop a microfluidic impedance platform for the characterization of endothelial barrier function during hydrodynamic stress.  For this purpose a device was fabricated that contains a circular region for cell monolayer growth that can be used to produce a rotational oscillatory fluid flow when the device is placed on an orbiting table.  Human Umbilical Vein Endothelial Cells (HUVECs) were cultured on the surface of the device, which contains patterned electrodes for recording impedance.  At various time points the impedance of the endothelial cells was recorded between 40Hz and 1.1MHz using AC of amplitude 10 millivolts.  A high-precision impedance analyzer (Agilent 4294A) and impedance probe (Agilent 42941A) were the instruments used for data acquisition.  In order to develop an appropriate circuit model to describe the behavior of the device the impedance data from static cell cultures was curve-fit using impedance analysis software (Scribner Associates ZView).  The results of the circuit model curve-fit demonstrated that cell monolayer resistance increases and capacitance decreases as the fraction of the device surface area that is covered by cells increases.  These changes in the electrical characteristics of the cell monolayer both contribute to higher impedance as reflected in the data when compared to the impedance of the device with media and attachment factor alone.  The future direction of this study is to analyze the impedance of the endothelial cells when they are subjected to hydrodynamic shear stress with the expectation that endothelial barrier function will become more permeable.

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