Quantification of propidium iodide delivery using millisecond electric pulses: experiments.

The transport mechanisms in electroporation-mediated molecular delivery are experimentally investigated and quantified. In particular, the uptake of propidium iodide (PI) into single 3T3 fibroblasts is investigated with time- and space-resolved fluorescence microscopy, and as a function of extracellular buffer conductivity. During the pulse, both the peak and the total integrated fluorescence intensity exhibit an inverse correlation with extracellular conductivity. This behavior can be explained by an electrokinetic phenomenon known as Field-Amplified Sample Stacking (FASS). Furthermore, the respective contributions from electrophoresis and diffusion have been quantified; the former is shown to be consistently higher than the latter for the experimental conditions considered. The results are compared with a compact model to predict electrophoresis-mediated transport, and good agreement is found between the two. The combination of the experimental and modeling efforts provides an effective means for the quantitative diagnosis of electroporation.