Date of Award

Spring 2012

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Electrical & Computer Engineering

Program/Concentration

Electrical Engineering

Committee Director

Juergen Kolb

Committee Member

Karl H. Schoenbach

Committee Member

Ravindra Joshi

Committee Member

Ali Beskok

Abstract

Nanosecond pulsed electric field induced biological effects have been a focus of research interests since the new millennium. Promising biomedical applications, e.g. tumor treatment and wound healing, are emerging based on this principle. Although the exact mechanisms behind the nanosecond pulse-cell interactions are not completely understood yet, it is generally believed that charging along the cell membranes (including intracellular membranes) and formation of membrane pores trigger subsequent biological responses, and the number and quality of pores are responsible for the cell fate. The immediate charging response of a biological cell to a nanosecond pulsed electric field exposure relies on the dielectric properties of its cellular components. Conversely, intense nanosecond pulses will change these properties due to conformational and functional changes. Hence, an understanding of biodielectric phenomena is necessary to explain the underlying interaction mechanisms between nanosecond pulses and biological materials.

To this end, we have investigated the changes in dielectric characteristics of biological cells and tissues after exposure to multiple nanosecond pulses. Significant differences have been observed in dielectric properties and membrane integrity of Jurkat cells for exposures to nanosecond and microsecond pulsed electric fields despite delivery of the same energy, suggesting different pore formation and development mechanisms. The effect of nanosecond pulsed electric fields on the dielectric properties of Jurkat cells is long-lasting which is consistent with predictions of much longer pore resealing times for shorter pulses. Strong correlation between short-term plasma membrane conductivity and long-term cell survival has also been observed for different nanosecond-exposure conditions. Together with the studies on tissues, we demonstrate that dielectric spectroscopy is capable of assessing conformational and possibly functional changes of cells after exposure to nanosecond pulsed electric fields on biologically relevant time scales, and in turn, evaluate and compare the efficacy of chosen pulse parameters.

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DOI

10.25777/79q1-z992

ISBN

9781267350312

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