Cell electrofusion using nanosecond electric pulses.

Electrofusion is an efficient method for fusing cells using short-duration high-voltage electric pulses. However, electrofusion yields are very low when fusion partner cells differ considerably in their size, since the extent of electroporation (consequently membrane fusogenic state) with conventionally used microsecond pulses depends proportionally on the cell radius. We here propose a new and innovative approach to fuse cells with shorter, nanosecond (ns) pulses.

Electroporation of intracellular liposomes using nanosecond electric pulses--a theoretical study.

Nanosecond (ns) electric pulses of sufficient amplitude can provoke electroporation of intracellular organelles. This paper investigates whether such pulses could provide a method for controlled intracellular release of a content of small internalized artificial lipid vesicles (liposomes). To estimate the pulse parameters needed to selectively electroporate liposomes while keeping the plasma and nuclear membranes intact, we constructed a numerical model of a biological cell containing a nucleus and liposomes of different sizes (with radii from 50 to 500 nm), which were placed in various sites in the cytoplasm.

The role of electrically stimulated endocytosis in gene electrotransfer.

Gene electrotransfer is an established method for transfer of genes into cells, however, the mechanism of transfer of DNA across the cell membrane is still not known. Some studies suggest that DNA is translocated through membrane pores while others propose that DNA enters the cell via electro-endocytosis, but no direct observation was performed. In this paper we investigated the second hypothesis.

Equivalent pulse parameters for electroporation.

Electroporation-based applications require the use of specific pulse parameters for a successful outcome. When recommended values of pulse parameters cannot be set, similar outcomes can be obtained by using equivalent pulse parameters. We determined the relations between the amplitude and duration/number of pulses resulting in the same fraction of electroporated cells.

Induced transmembrane voltage and its correlation with electroporation-mediated molecular transport.

Exposure of a cell to an electric field results in inducement of a voltage across its membrane (induced transmembrane voltage, DeltaPsi (m)) and, for sufficiently strong fields, in a transient increase of membrane permeability (electroporation). We review the analytical, numerical and experimental methods for determination of DeltaPsi (m) and a method for monitoring of transmembrane transport. We then combine these methods to investigate the correlation between DeltaPsi (m) and molecular transport through an electroporated membrane for isolated cells of regular and irregular shapes, for cells in dense suspensions as well as for cells in monolayer clusters.

Measuring the induced membrane voltage with Di-8-ANEPPS.

Placement of a cell into an external electric field causes a local charge redistribution inside and outside of the cell in the vicinity of the cell membrane, resulting in a voltage across the membrane. This voltage, termed the induced membrane voltage (also induced transmembrane voltage, or induced transmembrane potential difference) and denoted by DeltaPhi, exists only as long as the external field is present. If the resting voltage is present on the membrane, the induced voltage superimposes (adds) onto it.

A time-dependent numerical model of transmembrane voltage inducement and electroporation of irregularly shaped cells.

We describe a finite-element model of a realistic irregularly shaped biological cell in an external electric field that allows the calculation of time-dependent changes of the induced transmembrane voltage (Delta Psi) and simulation of cell membrane electroporation. The model was first tested by comparing its results to the time-dependent analytical solution for Delta Psi on a nonporated spherical cell, and a good agreement was obtained. To simulate electroporation, the model was extended by introducing a variable membrane conductivity.

Non invasive contact electrodes for in vivo localized cutaneous electropulsation and associated drug and nucleic acid delivery.

For an effective tissue controlled electropermeabilization as requested for electrochemotherapy and electrogenotherapy, it is very important to have informations about the electric field distribution provided by a defined set of electrodes. Computer simulations using the finite element models approach predicted the associated field distributions and currents. Phantoms made of gels with well-defined electrical conductance were used to measure the current responses of a new electrode geometry (wires), A good agreement between the measured and predicted currents was observed supporting the validity of the prediction for the field distribution.

Variability of the minimal transmembrane voltage resulting in detectable membrane electroporation.

We present a study of the variability of the minimal transmembrane voltage resulting in detectable electroporation of the plasma membrane of spherical and irregularly shaped CHO cells (we denote this voltage by ITVc). Electroporation was detected by monitoring the influx of Ca(2+), and the transmembrane voltage was computed on a 3D finite-elements model of each cell constructed from its cross-section images. We found that ITVc was highly variable, particularly in irregularly shaped cells, where it ranged from 512-1028 mV.

Kinetics of transmembrane transport of small molecules into electropermeabilized cells.

The transport of propidium iodide into electropermeabilized Chinese hamster ovary cells was monitored with a photomultiplier tube during and after the electric pulse. The influence of pulse amplitude and duration on the transport kinetics was investigated with time resolutions from 200 ns to 4 ms in intervals from 400 micros to 8 s. The transport became detectable as early as 60 micros after the start of the pulse, continued for tens of seconds after the pulse, and was faster and larger for higher pulse amplitudes and/or longer pulse durations.

Electropermeabilization of dense cell suspensions.

This paper investigates the influence of cell density on cell membrane electropermeabilization. The experiments were performed on dense cell suspensions (up to 400 x 10(6) cells/ml), which represent a simple model for studying electropermeabilization of tissues. Permeabilization was assayed with a fluorescence test using Propidium iodide to obtain the mean number of permeabilized cells (i.

Effect of cell electroporation on the conductivity of a cell suspension.

An increased permeability of a cell membrane during the application of high-voltage pulses results in increased transmembrane transport of molecules that otherwise cannot enter the cell. Increased permeability of a cell membrane is accompanied by increased membrane conductivity; thus, by measuring electric conductivity the extent of permeabilized tissue could be monitored in real time. In this article the effect of cell electroporation caused by high-voltage pulses on the conductivity of a cell suspension was studied by current-voltage measurements during and impedance measurement before and after the pulse application.

The effect of high frequency electric pulses on muscle contractions and antitumor efficiency in vivo for a potential use in clinical electrochemotherapy.

Muscle contractions present the main source of unpleasant sensations for patients undergoing electrochemotherapy. The contractions are a consequence of high voltage pulse delivery. Relatively low repetition frequency of these pulses (1 Hz) results in separate muscle contractions associated with each single pulse that is delivered.