Book Description

Reversible electroporation is a non-viral technique to introduce foreign molecules into biological cells or tissues, which has found applications in fields including gene transfer, cancer treatment, stem-cell research etc. Despite its promising potential, the improvement of electroporation technique is impeded by the lack of a comprehensive understanding of the underlying mechanisms involved in the process of molecular delivery. This work aims at implementing model studies of electroporation-mediated molecular delivery with the target varying from small molecules (propidium iodide, PI) to macromolecules (DNA). Three significant tasks have been accomplished. First, a model study is performed on the electroporation-mediated delivery of PI. In particular, the effects of extra-cellular conductivity on the amount of PI delivery are carefully investigated and discussed. The results are extensively compared with experiments by Sadik et al., and reveal important physical insights about the transport mechanisms involved. It is confirmed that the electrophoretic transport, not the diffusive transport, is the dominating mechanism in mediating PI delivery, and the inverse correlation observed between PI delivery and extra-cellular conductivity results from an electrokinetic phenomenon termed Field Amplified Sample Stacking (FASS). Second, a model investigation of Fluorescein-Dextran delivery is implemented for double-pulse electroporation. Simulated results find qualitative agreement with experiments in predicting the correlation between delivery and pulsing parameters. A bifurcation analysis of equilibrium pore size with respect to the transmembrane potential is presented to explain the observed "critical field strength" above which the second pulse abruptly becomes effective in mediating delivery. Third, a 1D Fokker-Planck simulation is used to characterize the process of DNA translocation through an electropore under finite DC pulses. It is found that the translocation may occur on two disparate time scales, the electrophoretic time (~ ms), and the diffusive time (~ s), depending on the pulse length. Furthermore, a power-law correlation is observed between the final probability of successful translocation and pulsing parameters. Simulated results are compared with previous data to interpret the trends, and further model predictions are made which can be verified by well-designed experiments. Together, these projects establish connections between available theoretical model and experimental observations in electroporation research. Such a connection on one hand benefits experimentalists in providing a powerful prediction tool for the design and optimization of electroporation; on the other hand it equally benefits theorists to improve the models and advance fundamental understandings in the subject.