Date of Award

Winter 2006

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Program/Concentration

Biomedical Sciences

Committee Director

Stephen J. Beebe

Committee Member

Peter F. Blackmore

Committee Member

Richard Nuccitelli

Committee Member

Karl H. Schoenbach

Abstract

The continuing effort to manipulate cell-signaling pathways for therapeutic benefit has lead to the exploration of electric field effects on cells. Current electric field applications include electroporation of the plasma membrane for introduction of drugs, genes, or other macromolecules into cells. Modeling of how these pulsed electric fields affect cells depicts the cell as an excitable circuit. In this model, the electric fields, administered in short pulses to a cell, charge the plasma and internal membranes, which act as dielectric layers, and between these the cytoplasm acts as a conductive medium. The pulse lengths of this treatment are traditionally in the range of 0.1 to 20 ms. Since the pulse duration is longer than the charging time of the plasma membrane the accumulation of charges along the membrane effectively shields the intracellular components from the imposed electric field much like a Faraday cage. With advances in pulsed power technology sub-microsecond pulses are now possible. This timescale is shorter than the charging time of the plasma membrane and therefore, during an applied field of sufficiently short duration and higher potential, charges are unable to accumulate sufficiently around the plasma membrane. This allows the applied field to be experienced throughout the interior of the cell. Thus it is proposed that pulsed electric fields of ultra short duration (<1 >μs) may manipulate specific intracellular functions. Based on molecular modeling of nanosecond duration pulsed electric fields (nsPEFs) the short duration of the pulse does not contribute to significant electroporation in the conventional sense. Rather a large number of nano-pores are formed, or supra-electroporation, that can limit large molecules from intracellular entry but may allow non-specific ion traffic. Therefore, nsPEFs are hypothesized to affect intracellular membrane structures providing a new means to modulate signal transduction mechanisms. This study investigated the effects of nsPEFs on induced calcium mobilization and changes in transmembrane potential in cultured cells. The results may further the development of nsPEFs as a basic investigative tool for discovery of new signaling pathways and stimulation of cell function. This application also holds promise as a possible medical treatment for tumor reduction and platelet activation.

DOI

10.25777/gghy-rb29

ISBN

9781109834994

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