Subnanosecond Electric Pulses Cause Membrane Permeabilization and Cell Death
ABSTRACT Subnanosecond electric pulses (200 ps) at electric field intensities on the order of 20 kV/cm cause the death of B16.F10 murine melanoma cells when applied for minutes with a pulse repetition rate of 10 kHz. The lethal effect of the ultrashort pulses is found to be caused by a combination of thermal effects and electrical effects. Studies on the cellular level show increased transport across the membrane at much lower exposure times or number of pulses. Exposed to 2000 pulses, NG108 cells exhibit an increase in membrane conductance, but only allow transmembrane currents to flow, if the medium is positively biased with respect to the cell interior. This means that the cell membrane behaves like a rectifying diode. This increase in membrane conductance is a nonthermal process, since the temperature rise due to the pulsing is negligible.
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ABSTRACT: Delivery of subnanosecond pulses into biological tissue can be undertaken by an impulse radiating antenna (IRA). Previous analysis shows that it is important to add a dielectric lens, which reduces the abrupt change of dielectric constant from air to tissue and therefore increases the transmission of the pulses. As a proof of concept, we have simulated subnanosecond pulsed radiation focused into a tissue simulant which consists of homogeneous, hemisphere tissues using 3-D electromagnetic solver, CST Microwave Studio. The simulation of an IRA in conjunction of a lens indicates subnanosecond pulses can be focused 6 cm below tissue surface with a spot diameter approximately 1 cm. The focal point coincides with the geometric focus of the IRA. However, this result is only valid for a tissue with a low conductivity (σ< 0.3 S/m). For lossier tissues, the electric field decreases from the surface monotonically as the subnanosecond pulses penetrate in depth. Two approaches were proposed to solve this problem. One was to use an inhomogeneous dielectric lens, with lossy material partially filled, to attenuate the incident field in the small azimuthal angles but to spare the field in the larger azimuthal angels. A desirable focusing was observed. The second approach was to use a dipole antenna in conjunction with the impulse radiating antenna. The dipole antenna decreases the surface field intensity generated by the aperture antenna, but at the destination, the field will be mostly given by the aperture antenna, resulting in a focusing.Power Modulator and High Voltage Conference (IPMHVC), 2012 IEEE International; 01/2012
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ABSTRACT: To expose biological cells or tissues to nanosecond pulsed electric fields of high intensity (>>kV/cm) and subnanosecond rise time, broadband exposure system with high-voltage handling capabilities and compatible with the tools of biologists are needed. To deliver subnanosecond pulses to a biological target, a hyperband antenna has been reported. In this study, we propose to use a Transverse ElectroMagnetic (TEM) cell. We characterize the system experimentally and numerically with Gaussian-like pulses of about 1.2 ns and 1.8 kV amplitude. The results are compared with those obtained using a classical electroporation cuvette, a typical delivery system to expose cell suspensions to ultrashort pulsed electric fields.Power Modulator and High Voltage Conference (IPMHVC), 2012 IEEE International; 01/2012
Conference Paper: Generators and Applicators for Nanosecond Pulsed Electric Field[Show abstract] [Hide abstract]
ABSTRACT: This paper describes nanosecond electric pulse generator and applicator for biological experiment. For the generator, an optoelectronic switching embedded in a frozen wave generator is obtained in the linear regime. In this way, square electrical pulses with adjustable duration and monocycle nanosecond pulses with balanced or unbalanced positive and negative components are obtained. In biological experiments, these nsPEF generators are frequently coupled with a standard electroporation cuvette, 50-Ω matched, containing the biological sample. A numerical and experimental characterization of a 50-Ω applicator is presented.Antennas and Propagation (EUCAP), 2012 6th European Conference on; 03/2012