Nanosecond pulsed electric field generators for the study of subcellular effects

Abstract

Modeling and experimental studies have shown that pulsed electric fields of nanosecond duration and megavolt per meter amplitude affect subcellular structures but do not lead to the formation of large pores in the outer membrane. This "intracellular electromanipulation" requires the use of pulse generators which provide extremely high power but low energy pulses. In this study, we describe the concept of the required pulsed power sources, their design, operation, and the necessary diagnostics. Two types of pulse generators based on the Blumlein line principle have been developed and are described here. One system is designed to treat a large number of cells in cuvettes holding volumes from 0.1 to 0.8 ml. Pulses of up to 40 kV amplitude, with a duration of 10 ns and a rise time close to 1 ns can be applied to the cuvette. For an electrode gap of 1 mm this voltage corresponds to an average electric field of 40 MV/m. The second system allows for real time observation of individual cells under a microscope. It generates pulses of 10-300 ns duration with a rise time of 3.5 ns and voltage amplitudes up to 1 kV. Connected to a microreactor with an electrode gap of 100 microm, electric fields up to 10 MV/m are applied.

Ultrashort electric pulse induced changes in cellular dielectric properties

“…After preparation, the cell suspensions were placed in Gene Pulser cuvettes (BioRad) with an electrode distance of 1 mm. A Blumlein pulse generator with an impedance of 10 X provided 10 ns electrical pulses with a rise-and fall-time of 1-2 ns, limited by the employed high-pressure SF 6 spark gap switch [16,18]. The Blumlein generator consists of two transmission lines with equal length and impedance in series with the load impedance matching the overall impedance of the two transmission lines, 2Z 0 .…”

“…The Blumlein generator consists of two transmission lines with equal length and impedance in series with the load impedance matching the overall impedance of the two transmission lines, 2Z 0 . More details can be found elsewhere [18].…”

“…TDDS uses the lumped capacitance approximation [14], which considers the sample holder as a capacitor with a complex permittivity that is determined by comparing the reflected signal of the sample to two standards (open and short circuit loads). We used a thermostat (Julabo, US) to maintain the temperature of the sample holder at 25°C to be consistent with past experiments [10,17,18].…”

“…Using data analysis software (IDC Expertise), we performed nonuniform sampling of a 5 ls time window to obtain the dielectric spectrum of the cell suspension and estimate and remove the effects of electrode polarization and DC conductivity [10,17,18]. We used a single-exponent model to correct for electrode polarization in the coaxial sample cell [19].…”

Nanosecond electric pulses penetrate the nucleus and enhance speckle formation

“…The Blumlein generator consists of two transmission lines with equal length and impedance in series with the load impedance matching the overall impedance of the two transmission lines, 2Z 0 . More details can be found elsewhere [15].…”