Theory of electroporation: A review

Biochemical and Biophysical Research Communications

et al. 2007

The interaction of nanosecond duration pulsed electric fields (nsPEFs) with biological cells, and the models describing this behavior, depend critically on the electrical properties of the cells being pulsed. Here, we used time domain dielectric spectroscopy to measure the dielectric properties of Jurkat cells, a malignant human T-cell line, before and after exposure to five 10 ns, 150 kV/cm electrical pulses. The cytoplasm and nucleoplasm conductivities decreased dramatically following pulsing, corresponding to previously observed rises in cell suspension conductivity. This suggests that electropermeabilization occurred, resulting in ion transport from the cell's interior to the exterior. A delayed decrease in cell membrane conductivity after the nsPEFs possibly suggests long-term ion channel damage or use dependence due to repeated membrane charging and discharging. This data could be used in models describing the phenomena at work. Ó 2007 Elsevier Inc. All rights reserved.Keywords: Dielectric spectroscopy; Nanosecond pulsed electric fields; Electroporation; Permeabilization; Plasma membrane; Time domain; Intracellular manipulation; Ultrashort pulsesThe permeability of the cell membrane to external molecules can be dramatically increased by applying pulsed electric fields (PEFs) above a threshold voltage [1]. The mechanism behind this electropermeabilization is electroporation, or pore formation in the cell membrane, and usually occurs for PEFs with electric fields on the order of a few kV/cm and pulse durations on the order of 0.1-10 ms. With the appropriate combination of these parameters, electroporation is irreversible and the membrane breaks down, which is desirable for applications ranging from bacterial decontamination to food processing [2]. Many applications require temporarily opening the cell membrane to normally impermeant molecules, such as electrochemotherapy and gene therapy [3]. Applying pulses with higher field strength (50-300 kV/cm) and shorter duration (10-300 ns) do not fully charge the cell membrane and instead interact primarily with the membranes of intracellular organelles [4]. These nanosecond duration PEFs (nsPEFs) cause intracellular calcium release [5,6] and apoptosis-induction in cell suspensions and in vivo tumors [5,7,8]. To better understand the mechanisms involved, attempts to develop mathematical models are underway 0006-291X/$ -see front matter Ó

Section: Discussionmentioning

confidence: 99%

“…Furthermore, the cell can recover (i.e. the pores reseal) as long as the pore radius remains below a certain critical radius, r crit [25,26]. While 10 ns pulses are generally too short to induce electroporation [4], applying multiple pulses charges the cell membrane more, increasing the likelihood of exceeding r crit [26].…”

Section: Discussionmentioning

confidence: 99%

Ultrashort electric pulse induced changes in cellular dielectric properties

Garner

Biochemical and Biophysical Research Communications

et al. 2007

“…The resulting delayed plasma membrane permeabilization was likely secondary, arising due to subcellular effects [2] rather than direct electroporation [18,19]. In previous confocal microscopic real time studies, we compared the nuclear and plasma membrane effects of 10 and 60 ns pulses of approximately the same energy [5].…”

Section: Discussionmentioning

confidence: 99%

Nanosecond electric pulses penetrate the nucleus and enhance speckle formation

Garner

Biochemical and Biophysical Research Communications

et al. 2007

Nanosecond electric pulses generate nanopores in the interior membranes of cells and modulate cellular functions. Here, we used confocal microscopy and flow cytometry to observe Smith antigen antibody (Y12) binding to nuclear speckles, known as small nuclear ribonucleoprotein particles (snRNPs) or intrachromatin granule clusters (IGCs), in Jurkat cells following one or five 10 ns, 150 kV/cm pulses. Using confocal microscopy and flow cytometry, we observed changes in nuclear speckle labeling that suggested a disruption of pre-messenger RNA splicing mechanisms. Pulse exposure increased the nuclear speckled substructures by 2.5-fold above basal levels while the propidium iodide (PI) uptake in pulsed cells was unchanged. The resulting nuclear speckle changes were also cell cycle dependent. These findings suggest that 10 ns pulses directly influenced nuclear processes, such as the changes in the nuclear RNA-protein complexes. Published by Elsevier Inc.Keywords: Nucleus; Nuclear speckles; Small nuclear ribonucleoprotein particles/intrachromatin granule clusters; Intracellular electromanipulation; Nanosecond electric pulsesWe have been exploring a new nanosecond (ns) time domain in cell biology. When cells are exposed to intense (50-300 kV/cm) pulsed electric fields (PEFs) with rise times faster than the time it takes for charges on the plasma membrane to redistribute, the electric field can penetrate into the interior of the cell and organelles. If these fields exceed the breakdown threshold of these membranes, nanopores will form in the organelle membranes [1,2]. To better understand the mechanism involved, mathematical models for the cellular electropermeabilization due to nsPEFs have been developed [3,4]. The resulting changes in cellular structures and functions differ significantly from traditional electroporation [microseconod to millisecond pulsed electric fields (PEFs)] [1,5,6]. Increased permeabilization of the plasma membrane, typically demonstrated by measuring propidium iodide (PI) uptake, due to nsPEFs was delayed compared to traditional electroporation [5,6], indicating that it was an indirect effect. These nsPEFs 0006-291X/$ -see front matter Published by Elsevier Inc.

“…From the voltage dependent membrane capacitance in the reversible electroporation region, the effective membrane thickness d can be determined as a function of the applied transmembrane voltage [25][26][27] , see figure 8.b. From the effective thickness d, the corresponding critical radius of nanopores can be determined from a model based on the membrane free energy 27 :…”

Section: Realization and Characterization Of A Membrane Fusion Eventmentioning

confidence: 99%

Fast membrane hemifusion via dewetting between lipid bilayers

2014

The behavior of lipid bilayer is important to understand the functionality of cells like the trafficking of ions between cells. Standard procedures to explore the properties of lipid bilayer and hemifused states typically use either supported membranes or vesicles. Both techniques have several shortcoming in terms of bio relevance or accessibility for measurements. In this article the formation of individual free standing hemifused states between model cell membranes is studied using an optimized microfluidic scheme wh ich allows for simultaneous optical and electrophysiological measurements. In a first step, two model membranes are formed at a desired location within a microfluidic device using a variation of the droplet interface bilayer (DiB) technique. In a second st ep, the two model membranes are brought into contact forming a single hemifused state. For all tested lipids, the hemifused state between free standing membranes form within hundreds of milliseconds, i.e. several orders of magnitude faster than reported in literature. The formation of a hemifused state is observed as a two stage process, whereas the second stage can be explained as a dewetting process in no-slip boundary condition. The formed hemifusion states are long living and a single fusion event can be observed when triggered by an applied electric field as demonstrated for monoolein.