Mechanistic studies of gene delivery into mammalian cells by electrical short-circuiting via an aqueous droplet in dielectric oil

Influence of DNA characteristics on cell membrane damage stimulated by electrical short-circuiting via a low-conductive aqueous droplet in dielectric oil

We investigated gene electrotransfer using electrical short-circuiting via a cell suspension droplet in dielectric oil. An aqueous droplet of a few microliters placed between a pair of electrodes can be deformed by an intense DC electric field depending on the electric field intensity. When a droplet containing suspended cells and plasmid DNA elongates during deformation and connects the electrodes, the resulting short circuit can cause successful gene electrotransfection into various mammalian cells. We also investigated the influence of the electroporation medium on membrane permeabilization and the mechanisms of gene electrotransfection using short-circuiting via an aqueous droplet. One aim of this study was to investigate the influence of the conductivity of electroporation medium on gene electrotransfer stimulated by short-circuiting. It was found that low-conductivity medium with plasmid DNA resulted in a significant decrease in cell viability compared to the high-conductivity medium with plasmid DNA. Therefore, we demonstrated the influence of exogenous DNA on membrane damage stimulated by droplet electroporation using a low-conductivity medium. Thus, electrical stimulation with the combination of plasmid DNA and the low-conductivity medium resulted in tremendous membrane damage. Linearized plasmid DNA stimulated more significant membrane damage than circular DNA. However, the size of linear DNA did not influence the efflux of small intracellular molecules.

Influence of Electroporation Medium on Delivery of Cell-Impermeable Small Molecules by Electrical Short-Circuiting via an Aqueous Droplet in Dielectric Oil: A Comparison of Different Fluorescent Tracers

Membrane permeabilization stimulated by high-voltage electric pulses has been used to deliver cell-impermeable exogenous molecules. The electric field effect on the cells depends on various experimental parameters, such as electric field strength, the number of electric pulses, and the electroporation medium. In this study, we show the influence of the electroporation medium on membrane permeabilization stimulated by electrical short-circuiting via an aqueous droplet in dielectric oil, a novel methodology developed by our previous investigations. We investigated the membrane permeabilization by three methods, influx of calcium ions, uptake of nucleic acid-binding fluorophores (YO-PRO-1), and calcein leakage. We demonstrated that the external medium conductivity had a significant impact on the cells in all described experiments. The short-circuiting using a low-conductivity electroporation medium enhanced the formation of both transient and irreversible membrane pores. We also found that clathrin-mediated endocytosis contributed to YO-PRO-1 uptake when a cell culture medium was used as an electroporation medium.