Electroporation applications continue to grow rapidly in number and significance in both basic research and medicine. A molecule of almost any size can be delivered into living cells by suitable electrical pulses. The most established clinical application is electrochemotherapy (ECT), which delivers small cancer drugs into targeted tumor cells. There is also great interest in delivering large molecules, particularly for DNA vaccination. Two other electroporation-mediated tumor ablation treatments are drug-free, based entirely on non-thermal electrical interactions that alter cell membranes. One is irreversible electroporation (IRE), which employs relatively large pulses that change a cell's outermost membrane. This leads to tumor cell death by necrosis. The other is based on nanosecond pulsed electric fields (nsPEF), which involve much larger but shorter pulses. These cause intracellular changes that kill targeted cells by apoptosis. In addition to affecting tumor cells, nearby nerve cells (which are larger, by nature) may be damaged even if they lie outside the targeted region. In spite of this exciting progress, the mechanisms underlying the desired outcomes and side effects remain poorly understood. We have succeeded in constructing increasingly realistic computer models of cells that describe essential features of electroporation. This is a difficult problem in which the cell's membranes change their electrical properties on a time scale of nanoseconds to milliseconds, which redistributes the electric field within the cell. Our general mechanistic hypothesis is that electrically created transient pores account for key features of non-thermal cell responses to strong electric field pulses. Pores are created, expand/contract and later vanish. The resulting molecular transport through the temporary pores can kill cells. The changing number and size of pores varies across a cell membrane. These govern transport of molecules of different size and charge. Molecular uptake and release is the result of all these processes taking place simultaneously at different sites within a cell. We propose extending our successful models to include several irregularly shaped cells close together, representing in vivo environments. These models should provide useful descriptions of molecular transport across even organelle membranes, and may lead to """"""""in silico"""""""" markers of cell death. This should set the stage for computer-based screening of electroporation pulse waveforms with different in vivo electrode configurations. The number of possible in vivo electrode configurations and EP pulse waveforms is essentially infinite and it is unrealistic to explore or evaluate these combinations by experiment alone. We thus expect that our increasingly realistic models can be used with the set of anatomically correct whole body models (""""""""Virtual Family"""""""") recently developed FDA/IT'IS to guide scientific understanding and to contribute to the medical device regulatory process.

Public Health Relevance

Electroporation applications continue to grow rapidly in both basic research and medicine, but the basic mechanisms remain poorly understood. We propose extending our successful models to represent cells within in vivo environments, which will provide useful descriptions of molecular transport within cells and may lead to in silico markers of cell death. Advanced multicell models can be used with the recently developed FDA/IT'IS anatomically correct Virtual Family models to guide scientific understanding and to assist medical device regulation.

National Institute of Health (NIH)
National Institute of General Medical Sciences (NIGMS)
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Special Emphasis Panel (ZRG1-SBIB-U (92))
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Lewis, Catherine D
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Massachusetts Institute of Technology
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Kotnik, Tadej; Weaver, James C (2016) Abiotic Gene Transfer: Rare or Rampant? J Membr Biol 249:623-631
Son, Reuben S; Gowrishankar, Thiruvallur R; Smith, Kyle C et al. (2016) Modeling a Conventional Electroporation Pulse Train: Decreased Pore Number, Cumulative Calcium Transport and an Example of Electrosensitization. IEEE Trans Biomed Eng 63:571-80
Son, Reuben S; Smith, Kyle C; Gowrishankar, Thiruvallur R et al. (2014) Basic features of a cell electroporation model: illustrative behavior for two very different pulses. J Membr Biol 247:1209-28
Smith, Kyle C; Son, Reuben S; Gowrishankar, T R et al. (2014) Emergence of a large pore subpopulation during electroporating pulses. Bioelectrochemistry 100:3-10
Weaver, James C (2013) Estimating the contribution of lightning to microbial evolution: guidance from the Drake equation: comment on ""Lightning-triggered electroporation and electrofusion as possible contributors to natural horizontal gene transfer"" by Tadej Kotnik. Phys Life Rev 10:373-6
Weaver, James C; Smith, Kyle C; Esser, Axel T et al. (2012) A brief overview of electroporation pulse strength-duration space: a region where additional intracellular effects are expected. Bioelectrochemistry 87:236-43
Smith, Kyle C; Weaver, James C (2012) Electrodiffusion of molecules in aqueous media: a robust, discretized description for electroporation and other transport phenomena. IEEE Trans Biomed Eng 59:1514-22
Smith, Kyle C; Weaver, James C (2011) Transmembrane molecular transport during versus after extremely large, nanosecond electric pulses. Biochem Biophys Res Commun 412:8-12
Gowrishankar, T R; Esser, A T; Smith, K C et al. (2011) Intracellular electroporation site distributions: modeling examples for nsPEF and IRE pulse waveforms. Conf Proc IEEE Eng Med Biol Soc 2011:732-5
Esser, Axel T; Smith, Kyle C; Gowrishankar, T R et al. (2010) Mechanisms for the intracellular manipulation of organelles by conventional electroporation. Biophys J 98:2506-14

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