A subnanosecond electric pulse exposure system for biological cells

Abstract

An exposure system adapted for use on a microscope stage was constructed for studying the effects of high electric field, subnanosecond pulses on biological cells. The system has a bandpass of 3 GHz and is capable of delivering high voltage electric pulses (6.2 kV) to the electrodes, which are two tungsten rods (100 μm in diameter) in parallel with a gap distance of 170 μm. Electric pulses are delivered to the electrodes through a π-network, which serves as an attenuator as well as an impedance matching unit to absorb the reflection at the electrodes. By minimizing the inductance of the pulse delivery system, it was possible to generate electric fields of up to 200 kV/cm with a pulse duration of 500 ps at the surface of the cover slip under the microscope. The electric field at the cover slip was found to be homogenous over an area of 50 to 70 μm. Within this area, neuroblastoma cells placed on the cover slip were studied with respect to membrane potential changes caused by subnanosecond pulses. This allowed us, for the first time, to demonstrate depolarization of the cell membrane potential.

3D bioprinter applied picosecond pulsed electric fields for targeted manipulation of proliferation and lineage specific gene expression in neural stem cells

“…When exposed to 3 kV/cm at 100 Hz an upregulation of GFAP in NSCs was recorded (12). GFAP upregulation was also seen when NCSs were exposed to 10 and 50 Hz AC signals at 1 V/cm (16). In mature astrocytes GFAP was upregulated in both astrocytes and microglia after exposure in an R-18 waveguide resonating at 1800 MHz (26).…”

“…Such a setup is not advisable for stimulating adhered cells such as functional neurons. The second setup is a coaxial cable which transitions into a pair of wire electrodes (16), which was adopted by this study for delivering pulses to adhered cells.…”

“…The electrode setup was based on a design described by Xiao et al (16). It consists of a coaxial cable and two tungsten wires (diameter: 0.1 mm).…”

Cell Fragmentation and Permeabilization by a 1 ns Pulse Driven Triple-Point Electrode

“…Still, a large field is needed to cause trypan blue uptake. For a cell that is rich in voltage-gated channels, a single subnanosecond pulse can permeabilize the membrane, presumably through the voltage-gated channels rather than the lipid bilayer, but the field is still rather high (~200 kV/cm) [6–8]. When subnanosecond pulses are applied repetitively, temperature increase contributes to the cell killing in addition to the pulsed electric field [9] and so the electric field can be effectively lowered to 20 kV/cm.…”

“…Recently, the technology to generate moderate or low voltage (<10 kV) subnanosecond pulses has advanced and generators are commercially available. Such low voltages allow us to generate electric fields that can be as high as 200 kV/cm with two wires in parallel for small-diameter electrodes and a short electrode gap distance [8]. It is also possible to use the triple-point effect to enhance the electric field near the metallic electrode with a low dielectric constant sleeve.…”