Date of Award

Fall 2003

Document Type

Thesis

Degree Name

Master of Science (MS)

Department

Electrical & Computer Engineering

Program/Concentration

Electrical Engineering

Committee Director

Karl H. Schoenbach

Committee Member

Ravindra P. Joshi

Committee Member

R. James Swanson

Call Number for Print

Special Collections LD4331.E55 G366 2003

Abstract

Pulsed electric fields (PEF's) above a certain voltage threshold cause electroporation for microsecond pulses and intracellular effects for submicrosecond pulses. Models describing these effects often depend on the electrical properties of the cell, which are altered by the PEF. Time domain dielectric spectroscopy was used to provide data for these models and to measure changes in the conductivity of HL-60 cell suspensions due to single 50 μs and 10 ns PEF's of the same energy. For 1.1 kV/cm, 50 μs pulses, the conductivity rose within a minute after the pulse and dropped dramatically approximately forty minutes after the pulse. For 78 kV/cm, 10 ns pulses, a brief delay occurred prior to the conductivity rise while the same drop in conductivity took place after approximately forty minutes. Trypan Blue exclusion tests showed that higher voltages frequently led to a loss of membrane integrity and a gradual recovery about thirty to forty minutes after the pulse. Higher voltages also led to increased scatter in Trypan Blue exclusion tests due to the increased stress placed on the cells. By applying a two-shell model, it was shown that a 50 μs pulse caused a much more significant rise in membrane conductivity than a 10 ns pulse of the same energy. The membrane conductivity decreased about fifteen minutes after both these pulses, which was consistent with membrane recovery. The membrane permittivity returned to normal for the 10 ns pulse, but continued to rise for the 50 μs pulse. This could indicate more significant, long-term membrane deformation in the case of the microsecond pulses.

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DOI

10.25777/1nd7-tk39

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