Electroporation-based treatments are motivated by the response of biological membranes to high- intensity pulsed electric fields. These fields rearrange the membrane structure to enhance the membrane's diffusive permeability, or the degree to which a membrane allows molecules to diffuse through it, is impacted by the structure, composition, and environment in which the cell resides. Tracer molecules have been developed that are unable to pass through intact cell membranes yet enter permeabilized cells. This dissertation investigates the hypothesis that the flow of such molecules may be used to quantify the effects of the electrical stimulus and environmental conditions leading to membrane electroporation. Specifically, a series of electrical pulses that alternates between positive and negative pulses permeabilizes cells more symmetrically than a longer pulse with the same total on-time. However, the magnitude of this symmetric entry decreases for the shorter alternating pulses. Furthermore, a method for quantitatively measuring the permeability of the cell membrane was proposed and validated. From data near the electroporation threshold, the response of cells varies widely in the manner in which cells become permeabilized. This method is applied to study the transient cell membrane permeability induced by electroporation and is used to demonstrate that the cell membrane remains permeable beyond 30 min following treatment. To analyze these experimental findings in the context of physical mechanisms, computational models of molecular uptake were developed to simulate electroporation. The results of these simulations indicate that the cell's local environment during electroporation facilitates the degree of molecular uptake. We use these models to predict how manipulating both the environment of cells during electroporation affects the induced membrane permeability. These experimental and computational results provide evidence that supports the hypothesis of this dissertation and provide a foundation for future investigation and simulation of membrane electroporation. / PHD / Electroporation is a biophysical process in which intense electric fields permeabilize bilayer membranes. The degree to which a membrane allows molecules to diffuse through it is called its diffusive permeability, and is impacted by the structure, composition, and environment in which the cell resides. This dissertation investigates the hypothesis that the flow of molecules into cells through their membranes may be used to quantitatively study the effects of the electrical stimulus and environmental conditions leading to membrane disruption. Here, I demonstrate that the cellular response to pulsed electric fields is affected by the waveform of the applied electrical stimulus. Specifically, a series of electrical pulses that alternates between positive and negative pulses permeabilizes cells more symmetrically than a longer pulse with the same total energized time. However, the total molecular uptake decreases for the shorter alternating pulses over the longer pulse. A method for quantitatively measuring the permeability of the cell membrane using a fluorescent tracer molecule is also developed and validated. This method is applied to show how cell membrane permeability changes following electroporation. To analyze these findings, computational models of molecular flow through the cell membrane are developed. These simulations indicate that the cell’s surrounding environment during electroporation dramatically impacts the degree of molecular uptake. We use these models to predict how manipulating both the environment of cells during electroporation affects the induced membrane permeability. These experimental and computational results provide a foundation for future investigation and simulation of membrane electroporation.
| Identifer | oai:union.ndltd.org:VTETD/oai:vtechworks.lib.vt.edu:10919/94416 |
| Date | 16 April 2018 |
| Creators | Sweeney, Daniel C. |
| Contributors | Department of Biomedical Engineering and Mechanics, Davalos, Rafael V., Cimini, Daniela, Verbridge, Scott, Poelzing, Steven, Safaai-Jazi, Ahmad |
| Publisher | Virginia Tech |
| Source Sets | Virginia Tech Theses and Dissertation |
| Detected Language | English |
| Type | Dissertation |
| Format | ETD, application/pdf |
| Rights | In Copyright, http://rightsstatements.org/vocab/InC/1.0/ |
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