| In the past two decades, electroporation has been found to be a very effective approach to introduce low and high molecular weight molecules such as drugs, hormones, proteins, DNA, and chromosomes into biological cells. Although electroporation has been under investigation for long time, the dynamic formation and resealing of pores is still not completely understood.; In this dissertation, we computationally analyzed the electric field dosimetry for the Gigahertz Transverse Electromagnetic (GTEM) chamber (a cell electroporation exposure system) loaded with cell culture media using the Finite-Difference Time-Domain (FDTD) method. The simulation results showed that the electric field intensity was high outside but very low inside the cell culture medium due to inefficient field coupling. Placing the cell-containing flasks on a high permittivity pedestal improved the field coupling. However, this exposure method still suffered from undesirable field polarity oscillations, even when excited by a monopolar ultrawideband pulse. Using a novel micro-fabricated microcuvette and pulse delivering system, we systematically conducted experimental studies of electroporation of HL-60 cells in the range of pulse widths from 125 ns to 1 ms, including the effects of pulse width, and the number of and intervals between pulses in a pulse train. The experimental results were consistent with previous publications and implied that the HL-60 cell membrane charge time is about 250 ns. Theoretical models based on the Smoluchowski equation were employed to describe the mechanisms for pore formation and development of a spherical (HL-60) cell. The calculation results showed that the pore dynamics, as well as the transmembrane potential and current density, were highly dependent on the polar angle on the cell membrane surface. A locally constrained surface tension model was proposed to represent the cytoskeleton and anchor proteins in the cell membrane and was observed to provide a plausible explanation for experimental evidence of long-lived pores. Also, transport mechanisms of small charged molecules associated with electroporation were analyzed based on the Nernst-Plank equation. The analysis showed that electrophoresis was the dominant transport process during the pulse, but diffusion contributed to most of the total dye uptake which primarily occurs after the pulse. |
