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Malakauskaitė P, Želvys A, Zinkevičienė A, Mickevičiūtė E, Radzevičiūtė-Valčiukė E, Malyško-Ptašinskė V, Lekešytė B, Novickij J, Kašėta V, Novickij V. Mitochondrial depolarization and ATP loss during high frequency nanosecond and microsecond electroporation. Bioelectrochemistry 2024; 159:108742. [PMID: 38776865 DOI: 10.1016/j.bioelechem.2024.108742] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2024] [Revised: 05/13/2024] [Accepted: 05/16/2024] [Indexed: 05/25/2024]
Abstract
It is predicted that ultra-short electric field pulses (nanosecond) can selectively permeabilize intracellular structures (e.g., mitochondria) without significant effects on the outer cell plasma membrane. Such a phenomenon would have high applicability in cancer treatment and could be employed to modulate cell death type or immunogenic response. Therefore, in this study, we compare the effects of 100 µs x 8 pulses (ESOPE - European Standard Operating Procedures on Electrochemotherapy) and bursts of 100 ns pulses for modulation of the mitochondria membrane potential. We characterize the efficacies of various protocols to trigger permeabilization, depolarize mitochondria (evaluated 1 h after treatment), the extent of ATP depletion and generation of reactive oxygen species (ROS). Finally, we employ the most prominent protocols in the context of Ca2+ electrochemotherapy in vitro. We provide experimental proof that 7.5-12.5 kV/cm x 100 ns pulses can be used to modulate mitochondrial potential, however, the permeabilization of the outer membrane is still a prerequisite for depolarization. Similar to 100 µs x 8 pulses, the higher the permeabilization rate, the higher the mitochondrial depolarization. Nevertheless, 100 ns pulses result in lesser ROS generation when compared to ESOPE, even when the energy input is several-fold higher than for the microsecond procedure. At the same time, it shows that even the short 100 ns pulses can be successfully used for Ca2+ electrochemotherapy, ensuring excellent cytotoxic efficacy.
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Affiliation(s)
- Paulina Malakauskaitė
- State Research Institute Centre for Innovative Medicine, Department of Immunology and Bioelectrochemistry, Vilnius, Lithuania; Vilnius Gediminas Technical University, Faculty of Electronics, Vilnius, Lithuania
| | - Augustinas Želvys
- State Research Institute Centre for Innovative Medicine, Department of Immunology and Bioelectrochemistry, Vilnius, Lithuania; Vilnius Gediminas Technical University, Faculty of Electronics, Vilnius, Lithuania
| | - Auksė Zinkevičienė
- State Research Institute Centre for Innovative Medicine, Department of Immunology and Bioelectrochemistry, Vilnius, Lithuania
| | - Eglė Mickevičiūtė
- State Research Institute Centre for Innovative Medicine, Department of Immunology and Bioelectrochemistry, Vilnius, Lithuania; Vilnius Gediminas Technical University, Faculty of Electronics, Vilnius, Lithuania
| | - Eivina Radzevičiūtė-Valčiukė
- State Research Institute Centre for Innovative Medicine, Department of Immunology and Bioelectrochemistry, Vilnius, Lithuania; Vilnius Gediminas Technical University, Faculty of Electronics, Vilnius, Lithuania
| | | | - Barbora Lekešytė
- State Research Institute Centre for Innovative Medicine, Department of Immunology and Bioelectrochemistry, Vilnius, Lithuania; Vilnius Gediminas Technical University, Faculty of Electronics, Vilnius, Lithuania
| | - Jurij Novickij
- Vilnius Gediminas Technical University, Faculty of Electronics, Vilnius, Lithuania
| | - Vytautas Kašėta
- State Research Institute Centre for Innovative Medicine, Department of Stem Cell Biology, Vilnius, Lithuania
| | - Vitalij Novickij
- State Research Institute Centre for Innovative Medicine, Department of Immunology and Bioelectrochemistry, Vilnius, Lithuania; Vilnius Gediminas Technical University, Faculty of Electronics, Vilnius, Lithuania.
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2
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VanderBurgh JA, Corso GT, Levy SL, Craighead HG. A multiplexed microfluidic continuous-flow electroporation system for efficient cell transfection. Biomed Microdevices 2024; 26:10. [PMID: 38194117 DOI: 10.1007/s10544-023-00692-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 12/13/2023] [Indexed: 01/10/2024]
Abstract
Cellular therapies have the potential to advance treatment for a broad array of diseases but rely on viruses for genetic reprogramming. The time and cost required to produce viruses has created a bottleneck that constricts development of and access to cellular therapies. Electroporation is a non-viral alternative for genetic reprogramming that bypasses these bottlenecks, but current electroporation technology suffers from low throughput, tedious optimization, and difficulty scaling to large-scale cell manufacturing. Here, we present an adaptable microfluidic electroporation platform with the capability for rapid, multiplexed optimization with 96-well plates. Once parameters are optimized using small volumes of cells, transfection can be seamlessly scaled to high-volume cell manufacturing without re-optimization. We demonstrate optimizing transfection of plasmid DNA to Jurkat cells, screening hundreds of different electrical waveforms of varying shapes at a speed of ~3 s per waveform using ~20 µL of cells per waveform. We selected an optimal set of transfection parameters using a low-volume flow cell. These parameters were then used in a separate high-volume flow cell where we obtained similar transfection performance by design. This demonstrates an alternative non-viral and economical transfection method for scaling to the volume required for producing a cell therapy without sacrificing performance. Importantly, this transfection method is disease-agnostic with broad applications beyond cell therapy.
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Affiliation(s)
| | - Grant T Corso
- CyteQuest, Inc, 95 Brown Road, Box 1011, Ithaca, NY, 14850, USA
| | - Stephen L Levy
- CyteQuest, Inc, 95 Brown Road, Box 1011, Ithaca, NY, 14850, USA
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3
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VanderBurgh JA, Corso GT, Levy SL, Craighead HG. A multiplexed microfluidic continuous-flow electroporation system for efficient cell transfection. RESEARCH SQUARE 2023:rs.3.rs-3538613. [PMID: 37986928 PMCID: PMC10659555 DOI: 10.21203/rs.3.rs-3538613/v1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/22/2023]
Abstract
Cellular therapies have the potential to advance treatment for a broad array of diseases but rely on viruses for genetic reprogramming. The time and cost required to produce viruses has created a bottleneck that constricts development of and access to cellular therapies. Electroporation is a non-viral approach for genetic reprogramming that bypasses these bottlenecks, but current electroporation technology suffers from low throughput, tedious optimization, and difficulty scaling to large-scale cell manufacturing. Here, we present an adaptable microfluidic electroporation platform with the capability for rapid, multiplexed optimization with 96-well plates. Once parameters are optimized using small volumes of cells, transfection can be seamlessly scaled to high-volume cell manufacturing without re-optimization. We demonstrate optimizing transfection of plasmid DNA to Jurkat cells, screening hundreds of different electrical waveforms of varying shapes at a speed of ~3 s per waveform using ~ 20 μL of cells per waveform. We selected an optimal set of transfection parameters using a low-volume flow cell. These parameters were then used in a separate high-volume flow cell where we obtained similar transfection performance by design. This demonstrates an economical method for scaling to the volume required for producing a cell therapy without sacrificing performance.
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4
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Łapińska Z, Novickij V, Rembiałkowska N, Szewczyk A, Dubińska-Magiera M, Kulbacka J, Saczko J. The influence of asymmetrical bipolar pulses and interphase intervals on the bipolar cancellation phenomenon in the ovarian cancer cell line. Bioelectrochemistry 2023; 153:108483. [PMID: 37301162 DOI: 10.1016/j.bioelechem.2023.108483] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2022] [Revised: 05/24/2023] [Accepted: 05/29/2023] [Indexed: 06/12/2023]
Abstract
The application of negative polarity electrical pulse (↓) following positive polarity pulses (↑) may induce bipolar cancellation (BPC), a unique physiological response believed to be specific to nanosecond electroporation (nsEP). The literature lacks analysis of bipolar electroporation (BP EP) involving asymmetrical sequences composed of nanosecond and microsecond pulses. Moreover, the impact of interphase interval on BPC caused by such asymmetrical pulse needs consideration. In this study, the authors utilized the ovarian clear carcinoma cell line (OvBH-1) model to investigate the BPC with asymmetrical sequences. Cells were exposed to pulses delivered in 10-pulse bursts but as uni- or bipolar, symmetrical, or asymmetrical sequences with a duration of 600 ns or 10 µs and electric field strength equal to 7.0 or 1.8 kV/cm, respectively. It was shown that the asymmetry of pulses influences BPC. The obtained results have also been investigated in the context of calcium electrochemotherapy. The reduction of cell membrane poration, and cell survival have been observed following Ca2+ electrochemotherapy. The effects of interphase delays (1 and 10 µs) on the BPC phenomenon were reported. Our findings show that the BPC phenomenon can be controlled using pulse asymmetry or delay between the positive and negative polarity of the pulse.
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Affiliation(s)
- Zofia Łapińska
- Department of Molecular and Cellular Biology, Faculty of Pharmacy, Wroclaw Medical University, Borowska 211A, 50-556 Wroclaw, Poland.
| | - Vitalij Novickij
- Institute of High Magnetic Fields, Vilnius Gediminas Technical University, LT-03227 Vilnius, Lithuania; Department of Immunology, State Research Institute Centre for Innovative Medicine, Santariškių 5, 08410 Vilnius, Lithuania
| | - Nina Rembiałkowska
- Department of Molecular and Cellular Biology, Faculty of Pharmacy, Wroclaw Medical University, Borowska 211A, 50-556 Wroclaw, Poland
| | - Anna Szewczyk
- Department of Molecular and Cellular Biology, Faculty of Pharmacy, Wroclaw Medical University, Borowska 211A, 50-556 Wroclaw, Poland
| | - Magdalena Dubińska-Magiera
- Department of Animal Developmental Biology, Faculty of Biological Science, University of Wroclaw, Sienkiewicza 21, 50-335 Wroclaw, Poland
| | - Julita Kulbacka
- Department of Molecular and Cellular Biology, Faculty of Pharmacy, Wroclaw Medical University, Borowska 211A, 50-556 Wroclaw, Poland; Department of Immunology, State Research Institute Centre for Innovative Medicine, Santariškių 5, 08410 Vilnius, Lithuania.
| | - Jolanta Saczko
- Department of Molecular and Cellular Biology, Faculty of Pharmacy, Wroclaw Medical University, Borowska 211A, 50-556 Wroclaw, Poland
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5
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Guo F, Zhou J, Wang J, Qian K, Qu H. A molecular dynamics study of phospholipid membrane electroporation induced by bipolar pulses with different intervals. Phys Chem Chem Phys 2023; 25:14096-14103. [PMID: 37161819 DOI: 10.1039/d2cp04637g] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/11/2023]
Abstract
The mechanism of changes in cell electroporation (EP) during the intervals of bipolar pulses is still unclear, and few studies have investigated the effect of the intervals at the molecular level. In this study, EP induced by bipolar pulses (BP) with different intervals was investigated using all-atom molecular dynamics simulations. Firstly, EP was formed during the positive pulses of 2 ns and 0.5 V nm-1, then the effects of various intervals of 0, 1, 5, and 10 ns on EP evolution were investigated, and the dynamic changes of different degrees of EP induced by the following negative pulses of 2 ns and 0.5 V nm-1 were analyzed. The elimination effect of intervals was determined and it was related to the degrees of EP and the time of intervals. At the last moment of the intervals the phospholipid membrane was classified and quantitatively defined in three states according to the degrees of EP, namely, Resealing, Destabilizing and Retaining states. These states appeared due to the combined effect of both the positive pulse and the interval, and the states represent the degrees of EP which had different responses after applying the negative pulse. These results can improve our understanding of the fundamental mechanism of BP-induced EP.
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Affiliation(s)
- Fei Guo
- Institute of Ecological Safety, Chongqing University of Posts and Telecommunications, Chongqing 400065, China.
| | - Jiong Zhou
- Institute of Ecological Safety, Chongqing University of Posts and Telecommunications, Chongqing 400065, China.
| | - Ji Wang
- Institute of Ecological Safety, Chongqing University of Posts and Telecommunications, Chongqing 400065, China.
| | - Kun Qian
- Institute of Ecological Safety, Chongqing University of Posts and Telecommunications, Chongqing 400065, China.
| | - Hongchun Qu
- Institute of Ecological Safety, Chongqing University of Posts and Telecommunications, Chongqing 400065, China.
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6
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Hartl S, Reinsch N, Füting A, Neven K. Pearls and Pitfalls of Pulsed Field Ablation. Korean Circ J 2023; 53:273-293. [PMID: 37161743 PMCID: PMC10172271 DOI: 10.4070/kcj.2023.0023] [Citation(s) in RCA: 8] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2023] [Accepted: 02/13/2023] [Indexed: 05/11/2023] Open
Abstract
Pulsed field ablation (PFA) was recently rediscovered as an emerging treatment modality for the ablation of cardiac arrhythmias. Ultra-short high voltage pulses are leading to irreversible electroporation of cardiac cells subsequently resulting in cell death. Current literature of PFA for pulmonary vein isolation (PVI) consistently reported excellent acute and long-term efficacy along with a very low adverse event rate. The undeniable benefit of the novel ablation technique is that cardiac cells are more susceptible to electrical fields whereas surrounding structures such as the pulmonary veins, the phrenic nerve or the esophagus are not, or if at all, minimally affected, which results in a favorable safety profile that is expected to be superior to the current standard of care without compromising efficacy. Nevertheless, the exact mechanisms of electroporation are not yet entirely understood on a cellular basis and pulsed electrical field protocols of different manufactures are not comparable among one another and require their own validation for each indication. Importantly, randomized controlled trials and comparative data to current standard of care modalities, such as radiofrequency- or cryoballoon ablation, are still missing. This review focuses on the "pearls" and "pitfalls" of PFA, a technology that has the potential to become the future leading energy source for PVI and beyond.
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Affiliation(s)
- Stefan Hartl
- Department of Electrophysiology, Alfried Krupp Hospital, Essen, Germany
- Department of Medicine, Witten/Herdecke University, Witten, Germany
| | - Nico Reinsch
- Department of Electrophysiology, Alfried Krupp Hospital, Essen, Germany
- Department of Medicine, Witten/Herdecke University, Witten, Germany
| | - Anna Füting
- Department of Electrophysiology, Alfried Krupp Hospital, Essen, Germany
- Department of Medicine, Witten/Herdecke University, Witten, Germany
| | - Kars Neven
- Department of Electrophysiology, Alfried Krupp Hospital, Essen, Germany
- Department of Medicine, Witten/Herdecke University, Witten, Germany.
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7
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VanderBurgh JA, Corso TN, Levy SL, Craighead HG. Scalable continuous-flow electroporation platform enabling T cell transfection for cellular therapy manufacturing. Sci Rep 2023; 13:6857. [PMID: 37185305 PMCID: PMC10133335 DOI: 10.1038/s41598-023-33941-2] [Citation(s) in RCA: 7] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2022] [Accepted: 04/21/2023] [Indexed: 05/17/2023] Open
Abstract
Viral vectors represent a bottleneck in the manufacturing of cellular therapies. Electroporation has emerged as an approach for non-viral transfection of primary cells, but standard cuvette-based approaches suffer from low throughput, difficult optimization, and incompatibility with large-scale cell manufacturing. Here, we present a novel electroporation platform capable of rapid and reproducible electroporation that can efficiently transfect small volumes of cells for research and process optimization and scale to volumes required for applications in cellular therapy. We demonstrate delivery of plasmid DNA and mRNA to primary human T cells with high efficiency and viability, such as > 95% transfection efficiency for mRNA delivery with < 2% loss of cell viability compared to control cells. We present methods for scaling delivery that achieve an experimental throughput of 256 million cells/min. Finally, we demonstrate a therapeutically relevant modification of primary T cells using CRISPR/Cas9 to knockdown T cell receptor (TCR) expression. This study displays the capabilities of our system to address unmet needs for efficient, non-viral engineering of T cells for cell manufacturing.
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Affiliation(s)
| | - Thomas N Corso
- CyteQuest, Inc, 95 Brown Road, Box 1011, Ithaca, NY, 14850, USA
| | - Stephen L Levy
- CyteQuest, Inc, 95 Brown Road, Box 1011, Ithaca, NY, 14850, USA
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8
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Zhou J, Hung YC, Xie X. Application of electric field treatment (EFT) for microbial control in water and liquid food. JOURNAL OF HAZARDOUS MATERIALS 2023; 445:130561. [PMID: 37055970 DOI: 10.1016/j.jhazmat.2022.130561] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/07/2022] [Revised: 11/23/2022] [Accepted: 12/04/2022] [Indexed: 06/19/2023]
Abstract
Water disinfection and food pasteurization are critical to reducing waterborne and foodborne diseases, which have been a pressing public health issue globally. Electrified treatment processes are emerging and have become promising alternatives due to the low cost of electricity, independence of chemicals, and low potential to form by-products. Electric field treatment (EFT) is a physical pathogen inactivation approach, which damages cell membrane by irreversible electroporation. EFT has been studied for both water disinfection and food pasteurization. However, no study has systematically connected the two fields with an up-to-date review. In this article, we first provide a comprehensive background of microbial control in water and food, followed by the introduction of EFT. Subsequently, we summarize the recent EFT studies for pathogen inactivation from three aspects, the processing parameters, its efficacy against different pathogens, and the impact of liquid properties on the inactivation performance. We also review the development of novel configurations and materials for EFT devices to address the current challenges of EFT. This review introduces EFT from an engineering perspective and may serve as a bridge to connect the field of environmental engineering and food science.
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Affiliation(s)
- Jianfeng Zhou
- School of Civil and Environmental Engineering, Georgia Institute of Technology, Atlanta, GA, USA
| | - Yen-Con Hung
- Department of Food Science and Technology, College of Agriculture and Environmental Sciences, University of Georgia, Griffin, GA, USA
| | - Xing Xie
- School of Civil and Environmental Engineering, Georgia Institute of Technology, Atlanta, GA, USA.
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9
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Zhou M, Zheng M, Zhou X, Tian S, Yang X, Ning Y, Li Y, Zhang S. The roles of connexins and gap junctions in the progression of cancer. Cell Commun Signal 2023; 21:8. [PMID: 36639804 PMCID: PMC9837928 DOI: 10.1186/s12964-022-01009-9] [Citation(s) in RCA: 9] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2022] [Accepted: 12/03/2022] [Indexed: 01/15/2023] Open
Abstract
Gap junctions (GJs), which are composed of connexins (Cxs), provide channels for direct information exchange between cells. Cx expression has a strong spatial specificity; however, its influence on cell behavior and information exchange between cells cannot be ignored. A variety of factors in organisms can modulate Cxs and subsequently trigger a series of responses that have important effects on cellular behavior. The expression and function of Cxs and the number and function of GJs are in dynamic change. Cxs have been characterized as tumor suppressors in the past, but recent studies have highlighted the critical roles of Cxs and GJs in cancer pathogenesis. The complex mechanism underlying Cx and GJ involvement in cancer development is a major obstacle to the evolution of therapy targeting Cxs. In this paper, we review the post-translational modifications of Cxs, the interactions of Cxs with several chaperone proteins, and the effects of Cxs and GJs on cancer. Video Abstract.
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Affiliation(s)
- Mingming Zhou
- grid.265021.20000 0000 9792 1228Graduate School, Tianjin Medical University, Tianjin, 300070 People’s Republic of China
| | - Minying Zheng
- Department of Pathology, Tianjin Union Medical Center, Nankai University, Tianjin, 300121 People’s Republic of China
| | - Xinyue Zhou
- grid.265021.20000 0000 9792 1228Graduate School, Tianjin Medical University, Tianjin, 300070 People’s Republic of China
| | - Shifeng Tian
- grid.265021.20000 0000 9792 1228Graduate School, Tianjin Medical University, Tianjin, 300070 People’s Republic of China
| | - Xiaohui Yang
- grid.216938.70000 0000 9878 7032Nankai University School of Medicine, Nankai University, Tianjin, 300071 People’s Republic of China
| | - Yidi Ning
- grid.216938.70000 0000 9878 7032Nankai University School of Medicine, Nankai University, Tianjin, 300071 People’s Republic of China
| | - Yuwei Li
- grid.417031.00000 0004 1799 2675Department of Colorectal Surgery, Tianjin Union Medical Center, Tianjin, 300121 People’s Republic of China
| | - Shiwu Zhang
- Department of Pathology, Tianjin Union Medical Center, Nankai University, Tianjin, 300121 People’s Republic of China
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Scuderi M, Dermol-Černe J, Amaral da Silva C, Muralidharan A, Boukany PE, Rems L. Models of electroporation and the associated transmembrane molecular transport should be revisited. Bioelectrochemistry 2022; 147:108216. [DOI: 10.1016/j.bioelechem.2022.108216] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2022] [Revised: 07/19/2022] [Accepted: 07/20/2022] [Indexed: 01/04/2023]
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11
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Garner AL, Neculaes B, Dylov DV. Infrared Laser-Based Single Cell Permeabilization by Plasma Membrane Temperature Gradients. MEMBRANES 2022; 12:membranes12060574. [PMID: 35736281 PMCID: PMC9227360 DOI: 10.3390/membranes12060574] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/01/2022] [Revised: 05/25/2022] [Accepted: 05/29/2022] [Indexed: 01/27/2023]
Abstract
Single cell microinjection provides precise tuning of the volume and timing of delivery into the treated cells; however, it also introduces workflow complexity that requires highly skilled operators and specialized equipment. Laser-based microinjection provides an alternative method for targeting a single cell using a common laser and a workflow that may be readily standardized. This paper presents experiments using a 1550 nm, 100 fs pulse duration laser with a repetition rate of 20 ns for laser-based microinjection and calculations of the hypothesized physical mechanism responsible for the experimentally observed permeabilization. Chinese Hamster Ovarian (CHO) cells exposed to this laser underwent propidium iodide uptake, demonstrating the potential for selective cell permeabilization. The agreement between the experimental conditions and the electropermeabilization threshold based on estimated changes in the transmembrane potential induced by a laser-induced plasma membrane temperature gradient, even without accounting for enhancement due to traditional electroporation, strengthens the hypothesis of this mechanism for the experimental observations. Compared to standard 800 nm lasers, 1550 nm fs lasers may ultimately provide a lower cost microinjection method that readily interfaces with a microscope and is agnostic to operator skill, while inducing fewer deleterious effects (e.g., temperature rise, shockwaves, and cavitation bubbles).
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Affiliation(s)
- Allen L. Garner
- School of Nuclear Engineering, Purdue University, West Lafayette, IN 47906, USA
- Elmore Family School of Electrical and Computer Engineering, Purdue University, West Lafayette, IN 47907, USA
- Department of Agricultural and Biological Engineering, Purdue University, West Lafayette, IN 47907, USA
- Correspondence: (A.L.G.); (B.N.)
| | - Bogdan Neculaes
- GE Research, Niskayuna, NY 12309, USA;
- Correspondence: (A.L.G.); (B.N.)
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12
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Sugrue A, Maor E, Del-Carpio Munoz F, Killu AM, Asirvatham SJ. Cardiac ablation with pulsed electric fields: principles and biophysics. Europace 2022; 24:1213-1222. [PMID: 35426908 DOI: 10.1093/europace/euac033] [Citation(s) in RCA: 21] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2021] [Accepted: 02/24/2022] [Indexed: 01/04/2023] Open
Abstract
Pulsed electric fields (PEFs) have emerged as an ideal cardiac ablation modality. At present numerous clinical trials in humans are exploring PEF as an ablation strategy for both atrial and ventricular arrhythmias, with early data showing significant promise. As this is a relatively new technology there is limited understanding of its principles and biophysics. Importantly, PEF biophysics and principles are starkly different to current energy modalities (radiofrequency and cryoballoon). Given the relatively novel nature of PEFs, this review aims to provide an understanding of the principles and biophysics of PEF ablation. The goal is to enhance academic research and ultimately enable optimization of ablation parameters to maximize procedure success and minimize risk.
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Affiliation(s)
- Alan Sugrue
- Division of Heart Rhythm Services, Department of Cardiovascular Medicine, Mayo Clinic, Rochester, MN, USA
- Division of Cardiovascular Medicine, Department of Medicine, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, Pennsylvania
| | - Elad Maor
- Division of Heart Rhythm Services, Department of Cardiovascular Medicine, Mayo Clinic, Rochester, MN, USA
- Chaim Sheba Medical Center and Sackler School of Medicine, Tel Aviv University, Israel
| | - Freddy Del-Carpio Munoz
- Division of Heart Rhythm Services, Department of Cardiovascular Medicine, Mayo Clinic, Rochester, MN, USA
| | - Ammar M Killu
- Division of Heart Rhythm Services, Department of Cardiovascular Medicine, Mayo Clinic, Rochester, MN, USA
| | - Samuel J Asirvatham
- Division of Heart Rhythm Services, Department of Cardiovascular Medicine, Mayo Clinic, Rochester, MN, USA
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13
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Zhou J, Hung YC, Xie X. Making waves: Pathogen inactivation by electric field treatment: From liquid food to drinking water. WATER RESEARCH 2021; 207:117817. [PMID: 34763276 DOI: 10.1016/j.watres.2021.117817] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/30/2021] [Revised: 09/25/2021] [Accepted: 10/25/2021] [Indexed: 06/13/2023]
Affiliation(s)
- Jianfeng Zhou
- School of Civil and Environmental Engineering, Georgia Institute of Technology, Atlanta, GA, USA
| | - Yen-Con Hung
- Department of Food Science and Technology, College of Agriculture and Environmental Sciences, University of Georgia, Griffin, GA, USA
| | - Xing Xie
- School of Civil and Environmental Engineering, Georgia Institute of Technology, Atlanta, GA, USA.
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Jindal S, Chockalingam S, Ghosh SS, Packirisamy G. Connexin and gap junctions: perspectives from biology to nanotechnology based therapeutics. Transl Res 2021; 235:144-167. [PMID: 33582245 DOI: 10.1016/j.trsl.2021.02.008] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/01/2020] [Revised: 01/10/2021] [Accepted: 02/09/2021] [Indexed: 12/11/2022]
Abstract
The concept of gap junctions and their role in intercellular communication has been known for around 50 years. Considerable progress has been made in understanding the fundamental biology of connexins in mediating gap junction intercellular communication (GJIC) and their role in various cellular processes including pathological conditions. However, this understanding has not led to development of advanced therapeutics utilizing GJIC. Inadequacies in strategies that target specific connexin protein in the affected tissue, with minimal or no collateral damage, are the primary reason for the lack of development of efficient therapeutic models. Herein, nanotechnology has a role to play, giving plenty of scope to circumvent these problems and develop more efficient connexin based therapeutics. AsODN, antisense oligodeoxynucleotides; BMPs, bone morphogenetic proteins; BMSCs, bone marrow stem cells; BG, bioglass; Cx, Connexin; CxRE, connexin-responsive elements; CoCr NPs, cobalt-chromium nanoparticles; cGAMP, cyclic guanosine monophosphate-adenosine monophosphate; cAMP, cyclic adenosine monophosphate; ERK1/2, extracellular signal-regulated kinase 1/2; EMT, epithelial-mesenchymal transition; EPA, eicosapentaenoic acids; FGFR1, fibroblast growth factor receptor 1; FRAP, fluorescence recovery after photobleaching; 5-FU, 5-fluorouracil; GJ, gap junction; GJIC, gap junctional intercellular communication; HGPRTase, hypoxanthine phosphoribosyltransferase; HSV-TK, herpes virus thymidine kinase; HSA, human serum albumin; HA, hyaluronic acid; HDAC, histone deacetylase; IRI, ischemia reperfusion injury; IL-6, interleukin-6; IL-8, interleukin-8; IONPs, iron-oxide nanoparticles; JNK, c-Jun N-terminal kinase; LAMP, local activation of molecular fluorescent probe; MSCs, mesenchymal stem cells; MMP, matrix metalloproteinase; MI, myocardial infarction; MAPK, mitogen-activated protein kinase; NF-κB, nuclear factor kappa B; NO, nitric oxide; PKC, protein kinase C; QDs, quantum dots; ROI, region of interest; RGO, reduced graphene oxide; siRNA, small interfering RNA; TGF-β1, transforming growth factor-β1; TNF-α, tumor necrosis factor-α; UCN, upconversion nanoparticles; VEGF, vascular endothelial growth factor. In this review, we discuss briefly the role of connexins and gap junctions in various physiological and pathological processes, with special emphasis on cancer. We further discuss the application of nanotechnology and tissue engineering in developing treatments for various connexin based disorders.
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Affiliation(s)
- Shlok Jindal
- Nanobiotechnology Laboratory, Department of Biotechnology, Indian Institute of Technology Roorkee, Roorkee, Uttarakhand, India
| | - S Chockalingam
- Department of Biotechnology, National Institute of Technology Warangal, Warangal, Telangana, India
| | - Siddhartha Sankar Ghosh
- Department of Biosciences and Bioengineering, Indian Institute of Technology Guwahati, Guwahati, Assam, India
| | - Gopinath Packirisamy
- Nanobiotechnology Laboratory, Department of Biotechnology, Indian Institute of Technology Roorkee, Roorkee, Uttarakhand, India; Centre for Nanotechnology, Indian Institute of Technology Roorkee, Roorkee, Uttarakhand, India.
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McBride S, Avazzadeh S, Wheatley AM, O’Brien B, Coffey K, Elahi A, O’Halloran M, Quinlan LR. Ablation Modalities for Therapeutic Intervention in Arrhythmia-Related Cardiovascular Disease: Focus on Electroporation. J Clin Med 2021; 10:jcm10122657. [PMID: 34208708 PMCID: PMC8235263 DOI: 10.3390/jcm10122657] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2021] [Revised: 06/13/2021] [Accepted: 06/14/2021] [Indexed: 02/06/2023] Open
Abstract
Targeted cellular ablation is being increasingly used in the treatment of arrhythmias and structural heart disease. Catheter-based ablation for atrial fibrillation (AF) is considered a safe and effective approach for patients who are medication refractory. Electroporation (EPo) employs electrical energy to disrupt cell membranes which has a minimally thermal effect. The nanopores that arise from EPo can be temporary or permanent. Reversible electroporation is transitory in nature and cell viability is maintained, whereas irreversible electroporation causes permanent pore formation, leading to loss of cellular homeostasis and cell death. Several studies report that EPo displays a degree of specificity in terms of the lethal threshold required to induce cell death in different tissues. However, significantly more research is required to scope the profile of EPo thresholds for specific cell types within complex tissues. Irreversible electroporation (IRE) as an ablative approach appears to overcome the significant negative effects associated with thermal based techniques, particularly collateral damage to surrounding structures. With further fine-tuning of parameters and longer and larger clinical trials, EPo may lead the way of adapting a safer and efficient ablation modality for the treatment of persistent AF.
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Affiliation(s)
- Shauna McBride
- Physiology and Cellular Physiology Laboratory, CÚRAM SFI Centre for Research in Medical Devices, School of Medicine, Human Biology Building, National University of Ireland (NUI) Galway, H91 W5P7 Galway, Ireland; (S.M.); (S.A.); (A.M.W.)
| | - Sahar Avazzadeh
- Physiology and Cellular Physiology Laboratory, CÚRAM SFI Centre for Research in Medical Devices, School of Medicine, Human Biology Building, National University of Ireland (NUI) Galway, H91 W5P7 Galway, Ireland; (S.M.); (S.A.); (A.M.W.)
| | - Antony M. Wheatley
- Physiology and Cellular Physiology Laboratory, CÚRAM SFI Centre for Research in Medical Devices, School of Medicine, Human Biology Building, National University of Ireland (NUI) Galway, H91 W5P7 Galway, Ireland; (S.M.); (S.A.); (A.M.W.)
| | - Barry O’Brien
- AtriAN Medical Limited, Unit 204, NUIG Business Innovation Centre, Upper Newcastle, H91 R6W6 Galway, Ireland; (B.O.); (K.C.)
| | - Ken Coffey
- AtriAN Medical Limited, Unit 204, NUIG Business Innovation Centre, Upper Newcastle, H91 R6W6 Galway, Ireland; (B.O.); (K.C.)
| | - Adnan Elahi
- Translational Medical Device Lab (TMDL), Lamb Translational Research Facility, University College Hospital Galway, H91 V4AY Galway, Ireland; (A.E.); (M.O.)
- Electrical & Electronic Engineering, School of Engineering, National University of Ireland Galway, H91 HX31 Galway, Ireland
| | - Martin O’Halloran
- Translational Medical Device Lab (TMDL), Lamb Translational Research Facility, University College Hospital Galway, H91 V4AY Galway, Ireland; (A.E.); (M.O.)
| | - Leo R. Quinlan
- Physiology and Cellular Physiology Laboratory, CÚRAM SFI Centre for Research in Medical Devices, School of Medicine, Human Biology Building, National University of Ireland (NUI) Galway, H91 W5P7 Galway, Ireland; (S.M.); (S.A.); (A.M.W.)
- CÚRAM, SFI Research Centre for Medical Devices, National University of Ireland Galway, H92 W2TY Galway, Ireland
- Correspondence:
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Aycock KN, Zhao Y, Lorenzo MF, Davalos RV. A Theoretical Argument for Extended Interpulse Delays in Therapeutic High-Frequency Irreversible Electroporation Treatments. IEEE Trans Biomed Eng 2021; 68:1999-2010. [PMID: 33400646 PMCID: PMC8291206 DOI: 10.1109/tbme.2021.3049221] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
High-frequency irreversible electroporation (H-FIRE) is a tissue ablation modality employing bursts of electrical pulses in a positive phase-interphase delay (d1)-negative phase-interpulse delay (d2) pattern. Despite accumulating evidence suggesting the significance of these delays, their effects on therapeutic outcomes from clinically-relevant H-FIRE waveforms have not been studied extensively. OBJECTIVE We sought to determine whether modifications to the delays within H-FIRE bursts could yield a more desirable clinical outcome in terms of ablation volume versus extent of tissue excitation. METHODS We used a modified spatially extended nonlinear node (SENN) nerve fiber model to evaluate excitation thresholds for H-FIRE bursts with varying delays. We then calculated non-thermal tissue ablation, thermal damage, and excitation in a clinically relevant numerical model. RESULTS Excitation thresholds were maximized by shortening d1, and extension of d2 up to 1,000 μs increased excitation thresholds by at least 60% versus symmetric bursts. In the ablation model, long interpulse delays lowered the effective frequency of burst waveforms, modulating field redistribution and reducing heat production. Finally, we demonstrate mathematically that variable delays allow for increased voltages and larger ablations with similar extents of excitation as symmetric waveforms. CONCLUSION Interphase and interpulse delays play a significant role in outcomes resulting from H-FIRE treatment. SIGNIFICANCE Waveforms with short interphase delays (d1) and extended interpulse delays (d2) may improve therapeutic efficacy of H-FIRE as it emerges as a clinical tissue ablation modality.
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Affiliation(s)
- Kenneth N. Aycock
- Department of Biomedical Engineering and Mechanics, Bioelectromechanical Systems Laboratory at Virginia Tech, Blacksburg, VA 24061 USA
| | - Yajun Zhao
- Department of Biomedical Engineering and Mechanics, Bioelectromechanical Systems Laboratory at Virginia Tech, Blacksburg, VA 24061 USA
| | - Melvin F. Lorenzo
- Department of Biomedical Engineering and Mechanics, Bioelectromechanical Systems Laboratory at Virginia Tech, Blacksburg, VA 24061 USA
| | - Rafael V. Davalos
- Department of Biomedical Engineering and Mechanics, Bioelectromechanical Systems Laboratory at Virginia Tech, Blacksburg, VA 24061 USA
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Wang L, Chang CC, Sylvers J, Yuan F. A statistical framework for determination of minimal plasmid copy number required for transgene expression in mammalian cells. Bioelectrochemistry 2020; 138:107731. [PMID: 33434786 DOI: 10.1016/j.bioelechem.2020.107731] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2020] [Revised: 12/11/2020] [Accepted: 12/14/2020] [Indexed: 02/07/2023]
Abstract
Plasmid DNA (pDNA) has been widely used for non-viral gene delivery. After pDNA molecules enter a mammalian cell, they may be trapped in subcellular structures or degraded by nucleases. Only a fraction of them can function as templates for transcription in the nucleus. Thus, an important question is, what is the minimal amount of pDNA molecules that need to be delivered into a cell for transgene expression? At present, it is technically a challenge to experimentally answer the question. To this end, we developed a statistical framework to establish the relationship between two experimentally quantifiable factors - average copy number of pDNA per cell among a group of cells after transfection and percent of the cells with transgene expression. The framework was applied to the analysis of electrotransfection under different experimental conditions in vitro. We experimentally varied the average copy number per cell and the electrotransfection efficiency through changes in extracellular pDNA dose, electric field strength, and pulse number. The experimental data could be explained or predicted quantitatively by the statistical framework. Based on the data and the framework, we could predict that the minimal number of pDNA molecules in the nucleus for transgene expression was on the order of 10. Although the prediction was dependent on the cell and experimental conditions used in the study, the framework may be generally applied to analysis of non-viral gene delivery.
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Affiliation(s)
- Liangli Wang
- Department of Biomedical Engineering, Duke University, Durham, NC 27708, USA
| | - Chun-Chi Chang
- Department of Biomedical Engineering, Duke University, Durham, NC 27708, USA
| | - Justin Sylvers
- Department of Biomedical Engineering, Duke University, Durham, NC 27708, USA
| | - Fan Yuan
- Department of Biomedical Engineering, Duke University, Durham, NC 27708, USA.
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Fesmire CC, Petrella RA, Kaufman JD, Topasna N, Sano MB. Irreversible electroporation is a thermally mediated ablation modality for pulses on the order of one microsecond. Bioelectrochemistry 2020; 135:107544. [DOI: 10.1016/j.bioelechem.2020.107544] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2020] [Revised: 04/29/2020] [Accepted: 04/29/2020] [Indexed: 12/15/2022]
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19
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Alobeedallah H, Cornell B, Coster H. The Effect of Cholesterol on the Voltage–Current Characteristics of Tethered Lipid Membranes. J Membr Biol 2020; 253:319-330. [DOI: 10.1007/s00232-020-00130-5] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2020] [Accepted: 07/09/2020] [Indexed: 11/28/2022]
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20
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Kašėta V, Kaušylė A, Kavaliauskaitė J, Petreikytė M, Stirkė A, Biziulevičienė G. Detection of intracellular biomarkers in viable cells using millisecond pulsed electric fields. Exp Cell Res 2020; 389:111877. [DOI: 10.1016/j.yexcr.2020.111877] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2019] [Revised: 01/06/2020] [Accepted: 01/24/2020] [Indexed: 01/22/2023]
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21
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Compact Square-Wave Pulse Electroporator with Controlled Electroporation Efficiency and Cell Viability. Symmetry (Basel) 2020. [DOI: 10.3390/sym12030412] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
The design and development of a compact square-wave pulse generator for the electroporation of biological cells is presented. This electroporator can generate square-wave pulses with durations from 3 μs up to 10 ms, voltage amplitudes up to 3500 V, and currents up to 250 A. The quantity of the accumulated energy is optimized by means of a variable capacitor bank. The pulse forming unit design uses a crowbar circuit, which gives better control of the pulse form and its duration, independent of the load impedance. In such cases, the square-wave pulse form ensures better control of electroporation efficiency by choosing parameters determined in advance. The device has an integrated graphic LCD screen and measurement modules for the visualization of the current pulse, allowing for express control of the electroporation quality and does not require an external oscilloscope for current pulse recording. This electroporator was tested on suspensions of Saccharomyces cerevisiae yeast cells, during which, it was demonstrated that the application of such square-wave pulses ensured better control of the electroporation efficiency and cell viability after treatment using the pulsed electric field (PEF).
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22
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Polajžer T, Dermol-Černe J, Reberšek M, O'Connor R, Miklavčič D. Cancellation effect is present in high-frequency reversible and irreversible electroporation. Bioelectrochemistry 2019; 132:107442. [PMID: 31923714 DOI: 10.1016/j.bioelechem.2019.107442] [Citation(s) in RCA: 31] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2019] [Revised: 12/03/2019] [Accepted: 12/05/2019] [Indexed: 12/21/2022]
Abstract
It was recently suggested that applying high-frequency short biphasic pulses (HF-IRE) reduces pain and muscle contractions in electrochemotherapy and irreversible ablation treatments; however, higher amplitudes with HF-IRE pulses are required to achieve a similar effect as with monophasic pulses. HF-IRE pulses are in the range of a microseconds, thus, the so-called cancellation effect could be responsible for the need to apply pulses of higher amplitudes. In cancellation effect, the effect of first pulse is reduced by the second pulse of opposite polarity. We evaluated cancellation effect with high-frequency biphasic pulses on CHO-K1 in different electroporation buffers. We applied eight bursts of 1-10 µs long pulses with inter-phase delays of 0.5 µs - 10 ms and evaluated membrane permeability and cell survival. In permeability experiments, cancellation effect was not observed in low-conductivity buffer. Cancellation effect was, however, observed in treatments with high-frequency biphasic pulses looking at survival in all of the tested electroporation buffers. In general, cancellation effect depended on inter-phase delay as well as on pulse duration, i.e. longer pulses and longer interphase delay cause less pronounced cancellation effect. Cancellation effect could be partially explained by the assisted discharge and not by the hyperpolarization by the chloride channels.
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Affiliation(s)
- Tamara Polajžer
- University of Ljubljana, Faculty of Electrical Engineering, Tržaška 25, 1000 Ljubljana, Slovenia
| | - Janja Dermol-Černe
- University of Ljubljana, Faculty of Electrical Engineering, Tržaška 25, 1000 Ljubljana, Slovenia
| | - Matej Reberšek
- University of Ljubljana, Faculty of Electrical Engineering, Tržaška 25, 1000 Ljubljana, Slovenia
| | - Rodney O'Connor
- École des Mines de Saint-Étienne, Department of Bioelectronics, Georges Charpak Campus, Centre Microélectronique de Provence, 880 Route de Mimet, 13120 Gardanne, France
| | - Damijan Miklavčič
- University of Ljubljana, Faculty of Electrical Engineering, Tržaška 25, 1000 Ljubljana, Slovenia.
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23
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Abstract
In this paper, we present an analysis and a validation of a simulation program with integrated circuit emphasis (SPICE) model for a pulse forming circuit of a high frequency electroporation system, which can deliver square-wave sub-microsecond (100–900 ns) electric field pulses. The developed SPICE model is suggested for use in evaluation of transient processes that occur due to high frequency operations in prototype systems. A controlled crowbar circuit was implemented to support a variety of biological loads and to ensure a constant electric pulse rise and fall time during electroporation to be independent of the applied buffer bioimpedance. The SPICE model was validated via a comparison of the simulation and experimental results obtained from the already existing prototype system. The SPICE model results were in good agreement with the experimental results, and the model complexity was found to be sufficient for analysis of transient processes. As result, the proposed SPICE model can be useful for evaluation and compensation of transient processes in sub-microsecond pulsed power set-ups during the development of new prototypes.
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Low concentrations of acetic and formic acids enhance the inactivation of Staphylococcus aureus and Pseudomonas aeruginosa with pulsed electric fields. BMC Microbiol 2019; 19:73. [PMID: 30943901 PMCID: PMC6448289 DOI: 10.1186/s12866-019-1447-1] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2018] [Accepted: 03/28/2019] [Indexed: 02/07/2023] Open
Abstract
Background Skin infections, particularly caused by drug-resistant pathogens, represent a clinical challenge due to being a frequent cause of morbidity and mortality. The objectives of this study were to examine if low concentrations of acetic and formic acids can increase sensitivity of Staphylococcus aureus and Pseudomonas aeruginosa to pulsed electric field (PEF) and thus, promote a fast and efficient treatment methodology for wound treatment. Results We have shown that the combination of PEF (10–30 kV/cm) with organic acids (0.1% formic and acetic acids) increased the bactericidal properties of treatment. The effect was apparent for both acids. The proposed methodology allowed to reduce the energy of electrical pulses and the inhibitory concentrations of acids, while still maintain high efficiency of bacteria eradication. Conclusions Application of weak organic acids as bactericidal agents has many advantages over antibiotics because they do not trigger development of drug-resistance in bacteria. The combination with PEF can make the treatment effective even against biofilms. The results of this study are particularly useful for the development of new methodologies for the treatment of extreme cases of wound infections when the chemical treatment is no longer effective or hinders wound healing.
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Simonis P, Kersulis S, Stankevich V, Sinkevic K, Striguniene K, Ragoza G, Stirke A. Pulsed electric field effects on inactivation of microorganisms in acid whey. Int J Food Microbiol 2019; 291:128-134. [PMID: 30496942 DOI: 10.1016/j.ijfoodmicro.2018.11.024] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2018] [Revised: 11/08/2018] [Accepted: 11/20/2018] [Indexed: 01/11/2023]
Abstract
Prospects of pulsed electric field technology application on acid whey concentrate pretreatment were analyzed. Stationary and flow pre-treatment systems were combined with different treatment parameters: electric field strength (E = 39 kV/cm, 95 kV/cm, 92 kV/cm), pulse duration (τ = 60 ns, 90 ns, 1000 ns) and pulse number (pn = up to 100 pulses). Isolates of Saccharomyces sp. and Lactobacillus sp. were predominant in concentrate. Significant non-thermal inactivation effect was achieved after PEF treatment. Exposure to short pulses selectively inactivated yeast cells, as a result PEF technology can be applied for low-energy acid whey processing.
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Affiliation(s)
- Povilas Simonis
- Laboratory of Bioelectrochemistry, State Research Institute, Center for Physical Sciences and Technology, Sauletekio ave. 3, LT-10257 Vilnius, Lithuania
| | - Skirmantas Kersulis
- High Power Pulse Laboratory, State Research Institute, Center for Physical Sciences and Technology, Sauletekio ave. 3, LT-10257, Vilnius, Lithuania
| | - Voitech Stankevich
- High Power Pulse Laboratory, State Research Institute, Center for Physical Sciences and Technology, Sauletekio ave. 3, LT-10257, Vilnius, Lithuania
| | - Kamilija Sinkevic
- Laboratory of Bioelectrochemistry, State Research Institute, Center for Physical Sciences and Technology, Sauletekio ave. 3, LT-10257 Vilnius, Lithuania
| | | | - Gregoz Ragoza
- Pieno Zvaigzdes Kaunas Department, Taikos ave. 90, LT-51181 Kaunas, Lithuania
| | - Arunas Stirke
- Laboratory of Bioelectrochemistry, State Research Institute, Center for Physical Sciences and Technology, Sauletekio ave. 3, LT-10257 Vilnius, Lithuania.
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Cronjé TF, Gaynor PT. Electroporation of Ishikawa cells: analysis by flow cytometry. IET Nanobiotechnol 2019; 13:58-65. [PMID: 30964039 PMCID: PMC8676626 DOI: 10.1049/iet-nbt.2018.5194] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2018] [Revised: 07/04/2018] [Accepted: 07/31/2018] [Indexed: 12/25/2022] Open
Abstract
Electroporation facilitates loading of cells with molecules and substances that are normally membrane impermeable. Flow cytometry is used in this study to examine the effects of the application of electroporation-level monopolar electric field pulses of varying electrical field strength on Ishikawa endometrial adenocarcinoma cells. Analysis of the fluorescence versus forward scatter plots corroborates the well-recognised threshold and cell size dependence characteristics of electroporation, but also shows the progression of cell lysis and generation of particulate material. Two 500 µs monopolar rectangular pulses ranging from 1.0 × 105 to 2.5 × 105 V/m were used to electroporate the cells. Electroporation yields (fraction of viable cells exhibiting significant propidium iodide uptake) ranged from 0 to 97%, with viability ranging between 78 and 34% over the electric field strength range tested. The higher electric field strength pulses not only reduced cell viability, but also generated a substantial amount of sub-cellular sized particulate material indicating cells have been physically disrupted enough to create these particles.
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Affiliation(s)
- Thomas F Cronjé
- Department of Engineering and Architectural Studies, Ara Institute of Canterbury, Christchurch, New Zealand.
| | - Paul T Gaynor
- Department of Electrical and Computer Engineering, University of Canterbury, Christchurch, New Zealand
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Weinert R, Pereira E, Ramos A. Inclusion of memory effects in a dynamic model of electroporation in biological tissues. Artif Organs 2019; 43:688-693. [PMID: 30589443 DOI: 10.1111/aor.13415] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2018] [Revised: 12/07/2018] [Accepted: 12/14/2018] [Indexed: 01/06/2023]
Abstract
This article presents experimental and computational results of electroporation in rat liver. The experiments were performed using different forms of electrodes and waveforms of applied electric pulses. For the numerical simulation, the electroporation model proposed by Ramos and Weinert in a previous publication was used. Dynamic adjustments were used for obtaining a good modeling of the electric current. A single set of model parameters was obtained to fit the simulated current response for different waveforms and electrodes. These parameters were obtained with the use of a genetic algorithm that minimized the error between the simulated and experimental currents. The electroporation model with dynamic adjustment proved to be an appropriate simulation tool to predict the tissue conductivity during stimulation by intense electrical fields.
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Affiliation(s)
- Rodolfo Weinert
- Universidade do Estado de Santa Catarina Ringgold Standard Institution, Electrical Engineering, Joinville, Brazil
| | - Eduardo Pereira
- Universidade do Estado de Santa Catarina Ringgold Standard Institution, Electrical Engineering, Joinville, Brazil
| | - Airton Ramos
- Universidade do Estado de Santa Catarina Ringgold Standard Institution, Electrical Engineering, Joinville, Brazil
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Wang L, Miller SE, Yuan F. Ultrastructural Analysis of Vesicular Transport in Electrotransfection. MICROSCOPY AND MICROANALYSIS : THE OFFICIAL JOURNAL OF MICROSCOPY SOCIETY OF AMERICA, MICROBEAM ANALYSIS SOCIETY, MICROSCOPICAL SOCIETY OF CANADA 2018; 24:553-563. [PMID: 30334512 PMCID: PMC6196718 DOI: 10.1017/s143192761801509x] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
Emerging evidence from various studies indicates that plasmid DNA (pDNA) is internalized by cells through an endocytosis-like process when it is used for electrotransfection. To provide morphological evidence of the process, we investigated ultrastructures in cells that were associated with the electrotransfected pDNA, using immunoelectron microscopy. The results demonstrate that four endocytic pathways are involved in the uptake of the pDNA, including caveolae- and clathrin-mediated endocytosis, macropinocytosis, and the clathrin-independent carrier/glycosylphosphatidylinositol-anchored protein-enriched early endosomal compartment (CLIC/GEEC) pathway. Among them, macropinocytosis is the most common pathway utilized by cells having various pDNA uptake capacities, and the CLIC/GEEC pathway is observed primarily in human umbilical vein endothelial cells. Quantitatively, the endocytic pathways are more active in easy-to-transfect cells than in hard-to-transfect ones. Taken together, our data provide ultrastructural evidence showing that endocytosis plays an important role in cellular uptake and intracellular transport of electrotransfected pDNA.
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Affiliation(s)
- Liangli Wang
- Department of Biomedical Engineering, Duke University, Durham, North Carolina 27708, USA
| | - Sara E. Miller
- Department of Pathology, Duke University Medical School, Durham, North Carolina 27710, USA
| | - Fan Yuan
- Department of Biomedical Engineering, Duke University, Durham, North Carolina 27708, USA
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The second phase of bipolar, nanosecond-range electric pulses determines the electroporation efficiency. Bioelectrochemistry 2018; 122:123-133. [PMID: 29627664 DOI: 10.1016/j.bioelechem.2018.03.014] [Citation(s) in RCA: 38] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2018] [Revised: 03/21/2018] [Accepted: 03/28/2018] [Indexed: 12/31/2022]
Abstract
Bipolar cancellation refers to a phenomenon when applying a second electric pulse reduces ("cancels") cell membrane damage by a preceding electric pulse of the opposite polarity. Bipolar cancellation is a reason why bipolar nanosecond electric pulses (nsEP) cause weaker electroporation than just a single unipolar phase of the same pulse. This study was undertaken to explore the dependence of bipolar cancellation on nsEP parameters, with emphasis on the amplitude ratio of two opposite polarity phases of a bipolar pulse. Individual cells (CHO, U937, or adult mouse ventricular cardiomyocytes (VCM)) were exposed to either uni- or bipolar trapezoidal nsEP, or to nanosecond electric field oscillations (NEFO). The membrane injury was evaluated by time-lapse confocal imaging of the uptake of propidium (Pr) or YO-PRO-1 (YP) dyes and by phosphatidylserine (PS) externalization. Within studied limits, bipolar cancellation showed little or no dependence on the electric field intensity, pulse repetition rate, chosen endpoint, or cell type. However, cancellation could increase for larger pulse numbers and/or for longer pulses. The sole most critical parameter which determines bipolar cancellation was the phase ratio: maximum cancellation was observed with the 2nd phase of about 50% of the first one, whereas a larger 2nd phase could add a damaging effect of its own. "Swapping" the two phases, i.e., delivering the smaller phase before the larger one, reduced or eliminated cancellation. These findings are discussed in the context of hypothetical mechanisms of bipolar cancellation and electroporation by nsEP.
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Cemazar M, Sersa G, Frey W, Miklavcic D, Teissié J. Recommendations and requirements for reporting on applications of electric pulse delivery for electroporation of biological samples. Bioelectrochemistry 2018; 122:69-76. [PMID: 29571034 DOI: 10.1016/j.bioelechem.2018.03.005] [Citation(s) in RCA: 34] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2018] [Revised: 03/09/2018] [Accepted: 03/10/2018] [Indexed: 01/26/2023]
Abstract
Electric field-induced membrane changes are an important approach in the life sciences. However, the developments in knowledge and translational applications face problems of reproducibility. Indeed, a quick survey of the literature reveals a lack of transparent and comprehensive reporting of essential technical information in many papers. Too many of the published scientific papers do not contain sufficient information for proper assessment of the presented results. The general rule/guidance in reporting experimental data should require details on exposure conditions such that other researchers are able to evaluate, judge and reproduce the experiments and data obtained. To enhance dissemination of information and reproducibility of protocols, it is important to agree upon nomenclature and reach a consensus on documentation of experimental methods and procedures. This paper offers recommendations and requirements for reporting on applications of electric pulse delivery for electroporation of biological samples in life science.
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Affiliation(s)
- M Cemazar
- Department of Experimental Oncology, Institute of Oncology, Ljubljana, Zaloska 2, 1000 Ljubljana, Slovenia; Faculty of Health Sciences, University of Primorska, Polje, 42, 6310 Izola, Slovenia
| | - G Sersa
- Department of Experimental Oncology, Institute of Oncology, Ljubljana, Zaloska 2, 1000 Ljubljana, Slovenia
| | - W Frey
- Karlsruhe Institute of Technology (KIT), Institute for Pulsed Power and Microwave Technology (IHM), 76344 Eggenstein-Leopoldshafen, Germany
| | - D Miklavcic
- University of Ljubljana, Faculty of Electrical Engineering, Trzaska 25, 1000 Ljubljana, Slovenia
| | - J Teissié
- Institut de Pharmacologie et Biologie Structurale, IPBS, Université de Toulouse, CNRS, UPS, Toulouse, France.
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García-Sánchez T, Merla C, Fontaine J, Muscat A, Mir LM. Sine wave electropermeabilization reveals the frequency-dependent response of the biological membranes. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2018; 1860:1022-1034. [PMID: 29410049 DOI: 10.1016/j.bbamem.2018.01.018] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/04/2017] [Revised: 01/16/2018] [Accepted: 01/22/2018] [Indexed: 01/25/2023]
Abstract
The permeabilization of biological membranes by electric fields, known as electroporation, has been traditionally performed with square electric pulses. These signals distribute the energy applied to cells in a wide frequency band. This paper investigates the use of sine waves, which are narrow band signals, to provoke electropermeabilization and the frequency dependence of this phenomenon. Single bursts of sine waves at different frequencies in the range from 8 kHz-130 kHz were applied to cells in vitro. Electroporation was studied in the plasma membrane and the internal organelles membrane using calcium as a permeabilization marker. Additionally, a double-shell electrical model was simulated to give a theoretical framework to our results. The electroporation efficiency shows a low pass filter frequency dependence for both the plasma membrane and the internal organelles membrane. The mismatch between the theoretical response and the observed behavior for the internal organelles membrane is explained by a two-step permeabilization process: first the permeabilization of the external membrane and afterwards that of the internal membranes. The simulations in the model confirm this two-step hypothesis when a variable plasma membrane conductivity is considered in the analysis. This study demonstrates how the use of narrow-band signals as sine waves is a suitable method to perform electroporation in a controlled manner. We suggest that the use of this type of signals could bring a simplification in the investigations of the very complex phenomenon of electroporation, thus representing an interesting option in future fundamental studies.
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Affiliation(s)
- Tomás García-Sánchez
- Vectorology and Anticancer Therapies, UMR 8203, CNRS, Univ. Paris-Sud, Gustave Roussy, Université Paris-Saclay, 94805 Villejuif, France.
| | - Caterina Merla
- Vectorology and Anticancer Therapies, UMR 8203, CNRS, Univ. Paris-Sud, Gustave Roussy, Université Paris-Saclay, 94805 Villejuif, France
| | - Jessica Fontaine
- Vectorology and Anticancer Therapies, UMR 8203, CNRS, Univ. Paris-Sud, Gustave Roussy, Université Paris-Saclay, 94805 Villejuif, France
| | - Adeline Muscat
- Vectorology and Anticancer Therapies, UMR 8203, CNRS, Univ. Paris-Sud, Gustave Roussy, Université Paris-Saclay, 94805 Villejuif, France
| | - Lluis M Mir
- Vectorology and Anticancer Therapies, UMR 8203, CNRS, Univ. Paris-Sud, Gustave Roussy, Université Paris-Saclay, 94805 Villejuif, France
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High frequency electroporation efficiency is under control of membrane capacitive charging and voltage potential relaxation. Bioelectrochemistry 2018; 119:92-97. [DOI: 10.1016/j.bioelechem.2017.09.006] [Citation(s) in RCA: 34] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2017] [Revised: 09/13/2017] [Accepted: 09/13/2017] [Indexed: 01/13/2023]
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Bednarczyk M, Kozłowska I, Łakota P, Szczerba A, Stadnicka K, Kuwana T. Generation of transgenic chickens by the non-viral, cell-based method: effectiveness of some elements of this strategy. J Appl Genet 2018; 59:81-89. [PMID: 29372515 PMCID: PMC5799318 DOI: 10.1007/s13353-018-0429-6] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2017] [Revised: 01/05/2018] [Accepted: 01/10/2018] [Indexed: 12/20/2022]
Abstract
Transgenic chickens have, in general, been produced by two different procedures. The first procedure is based on viral transfection systems. The second procedure, the non-viral method, is based on genetically modified embryonic cells transferred directly into the recipient embryo. In this review, we analyzed the effectiveness of important elements of the non-viral, cell-based strategy of transgenic chicken production. The main elements of this strategy are: isolation and cultivation of donor embryonic cells; transgene construction; cell transfection in vitro; and chimera production: injection of cells into recipient embryos, raising and identification of germline chimeras, mating germline chimeras, transgene inheritance, and transgene expression. In this overview, recent progress and important limitations in the development of transgenic chickens are presented.
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Affiliation(s)
- Marek Bednarczyk
- Department of Animal Biochemistry and Biotechnology, University of Science and Technology, Bydgoszcz, Poland.
| | - Izabela Kozłowska
- Department of Animal Biochemistry and Biotechnology, University of Science and Technology, Bydgoszcz, Poland
| | - Paweł Łakota
- Department of Animal Biochemistry and Biotechnology, University of Science and Technology, Bydgoszcz, Poland
| | - Agata Szczerba
- Department of Animal Biochemistry and Biotechnology, University of Science and Technology, Bydgoszcz, Poland
| | - Katarzyna Stadnicka
- Department of Animal Biochemistry and Biotechnology, University of Science and Technology, Bydgoszcz, Poland
| | - Takashi Kuwana
- Department of Animal Biochemistry and Biotechnology, University of Science and Technology, Bydgoszcz, Poland
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34
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Sweeney DC, Weaver JC, Davalos RV. Characterization of Cell Membrane Permeability In Vitro Part I: Transport Behavior Induced by Single-Pulse Electric Fields. Technol Cancer Res Treat 2018; 17:1533033818792491. [PMID: 30236040 PMCID: PMC6154305 DOI: 10.1177/1533033818792491] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2018] [Revised: 06/18/2018] [Accepted: 07/03/2018] [Indexed: 02/03/2023] Open
Abstract
Most experimental studies of electroporation focus on permeabilization of the outer cell membrane. Some experiments address delivery of ions and molecules into cells that should survive; others focus on efficient killing of the cells with minimal temperature rise. A basic method for quantifying electroporation effectiveness is measuring the membrane's diffusive permeability. More specifically, comparisons of membrane permeability between electroporation protocols often rely on relative fluorescence measurements, which are not able to be directly connected to theoretical calculations and complicate comparisons between studies. Here we present part I of a 2-part study: a research method for quantitatively determining the membrane diffusive permeability for individual cells using fluorescence microscopy. We determine diffusive permeabilities of cell membranes to propidium for electric field pulses with durations of 1 to 1000 μs and strengths of 170 to 400 kV/m and show that diffusive permeabilities can reach 1.3±0.4×10-8 m/s. This leads to a correlation between increased membrane permeability and eventual propidium uptake. We also identify a subpopulation of cells that exhibit a delayed and significant propidium uptake for relatively small single pulses. Our results provide evidence that cells, especially those that uptake propidium more slowly, can achieve large permeabilities with a single electrical pulse that may be quantitatively measured using standard fluorescence microscopy equipment and techniques.
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Affiliation(s)
- Daniel C. Sweeney
- Department of Biomedical Engineering and Mechanics, Virginia Tech,
Blacksburg, VA, USA
| | - James C. Weaver
- Harvard-MIT Division of Health Sciences and Technology, Massachusetts
Institute of Technology, Cambridge, MA, USA
| | - Rafael V. Davalos
- Department of Biomedical Engineering and Mechanics, Virginia Tech,
Blacksburg, VA, USA
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35
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Sweeney DC, Douglas TA, Davalos RV. Characterization of Cell Membrane Permeability In Vitro Part II: Computational Model of Electroporation-Mediated Membrane Transport. Technol Cancer Res Treat 2018; 17:1533033818792490. [PMID: 30231776 PMCID: PMC6149036 DOI: 10.1177/1533033818792490] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2018] [Revised: 06/18/2018] [Accepted: 07/03/2018] [Indexed: 12/22/2022] Open
Abstract
Electroporation is the process by which applied electric fields generate nanoscale defects in biological membranes to more efficiently deliver drugs and other small molecules into the cells. Due to the complexity of the process, computational models of cellular electroporation are difficult to validate against quantitative molecular uptake data. In part I of this two-part report, we describe a novel method for quantitatively determining cell membrane permeability and molecular membrane transport using fluorescence microscopy. Here, in part II, we use the data from part I to develop a two-stage ordinary differential equation model of cellular electroporation. We fit our model using experimental data from cells immersed in three buffer solutions and exposed to electric field strengths of 170 to 400 kV/m and pulse durations of 1 to 1000 μs. We report that a low-conductivity 4-(2-hydroxyethyl)-1 piperazineethanesulfonic acid buffer enables molecular transport into the cell to increase more rapidly than with phosphate-buffered saline or culture medium-based buffer. For multipulse schemes, our model suggests that the interpulse delay between two opposite polarity electric field pulses does not play an appreciable role in the resultant molecular uptake for delays up to 100 μs. Our model also predicts the per-pulse permeability enhancement decreases as a function of the pulse number. This is the first report of an ordinary differential equation model of electroporation to be validated with quantitative molecular uptake data and consider both membrane permeability and charging.
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Affiliation(s)
- Daniel C. Sweeney
- Department of Biomedical Engineering and Mechanics, Virginia Tech,
Blacksburg, VA, USA
| | - Temple A. Douglas
- Department of Biomedical Engineering and Mechanics, Virginia Tech,
Blacksburg, VA, USA
| | - Rafael V. Davalos
- Department of Biomedical Engineering and Mechanics, Virginia Tech,
Blacksburg, VA, USA
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36
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Krishnaveni S, Subhashini R, Rajini V. Inactivation of bacteria suspended in water by using high frequency unipolar pulse voltage. J FOOD PROCESS ENG 2017. [DOI: 10.1111/jfpe.12574] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- S. Krishnaveni
- Department of EEE; SSN College of Engineering, Kalavakkam-603 110; Chennai Tamil Nadu, India
| | - R. Subhashini
- Department of Biomedical Engineering; SSN College of Engineering, Kalavakkam-603 110; Chennai Tamil Nadu India
| | - V. Rajini
- Department of EEE; SSN College of Engineering, Kalavakkam-603 110; Chennai Tamil Nadu, India
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37
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Garcia PA, Ge Z, Kelley LE, Holcomb SJ, Buie CR. High efficiency hydrodynamic bacterial electrotransformation. LAB ON A CHIP 2017; 17:490-500. [PMID: 28067371 DOI: 10.1039/c6lc01309k] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/15/2023]
Abstract
Synthetic biology holds great potential for addressing pressing challenges for mankind and our planet. One technical challenge in tapping into the full potential of synthetic biology is the low efficiency and low throughput of genetic transformation for many types of cells. In this paper, we discuss a novel microfluidic system for improving bacterial electrotransformation efficiency and throughput. Our microfluidic system is comprised of non-uniform constrictions in microchannels to facilitate high electric fields with relatively small applied voltages to induce electroporation. Additionally, the microfluidic device has regions of low electric field to assist in electrophoretic transport of nucleic acids into the cells. The device features hydrodynamically controlled electric fields that allow cells to experience a time dependent electric field that is otherwise difficult to achieve using standard electronics. Results suggest that transformation efficiency can be increased by ∼4×, while throughput can increase by 100-1000× compared to traditional electroporation cuvettes. This work will enable high-throughput and high efficiency genetic transformation of microbes, facilitating accelerated development of genetically engineered organisms.
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Affiliation(s)
- Paulo A Garcia
- Department of Mechanical Engineering, Massachusetts Institute of Technology, 77 Massachusetts Ave, Cambridge, MA 02139, USA.
| | - Zhifei Ge
- Department of Mechanical Engineering, Massachusetts Institute of Technology, 77 Massachusetts Ave, Cambridge, MA 02139, USA.
| | - Laura E Kelley
- Department of Biological Engineering, Massachusetts Institute of Technology, 77 Massachusetts Ave, Cambridge, MA 02139, USA
| | - Steven J Holcomb
- Department of Mechanical Engineering, Massachusetts Institute of Technology, 77 Massachusetts Ave, Cambridge, MA 02139, USA.
| | - Cullen R Buie
- Department of Mechanical Engineering, Massachusetts Institute of Technology, 77 Massachusetts Ave, Cambridge, MA 02139, USA.
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38
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Effects of Electroporation on Tamoxifen Delivery in Estrogen Receptor Positive (ER+) Human Breast Carcinoma Cells. Cell Biochem Biophys 2016; 75:103-109. [DOI: 10.1007/s12013-016-0776-z] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2016] [Accepted: 11/30/2016] [Indexed: 12/11/2022]
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39
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Novickij V, Grainys A, Lastauskienė E, Kananavičiūtė R, Pamedytytė D, Kalėdienė L, Novickij J, Miklavčič D. Pulsed Electromagnetic Field Assisted in vitro Electroporation: A Pilot Study. Sci Rep 2016; 6:33537. [PMID: 27634482 PMCID: PMC5025861 DOI: 10.1038/srep33537] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2016] [Accepted: 08/30/2016] [Indexed: 12/21/2022] Open
Abstract
Electroporation is a phenomenon occurring due to exposure of cells to Pulsed Electric Fields (PEF) which leads to increase of membrane permeability. Electroporation is used in medicine, biotechnology, and food processing. Recently, as an alternative to electroporation by PEF, Pulsed ElectroMagnetic Fields (PEMF) application causing similar biological effects was suggested. Since induced electric field in PEMF however is 2–3 magnitudes lower than in PEF electroporation, the membrane permeabilization mechanism remains hypothetical. We have designed pilot experiments where Saccharomyces cerevisiae and Candida lusitaniae cells were subjected to single 100–250 μs electrical pulse of 800 V with and without concomitant delivery of magnetic pulse (3, 6 and 9 T). As expected, after the PEF pulses only the number of Propidium Iodide (PI) fluorescent cells has increased, indicative of membrane permeabilization. We further show that single sub-millisecond magnetic field pulse did not cause detectable poration of yeast. Concomitant exposure of cells to pulsed electric (PEF) and magnetic field (PMF) however resulted in the increased number PI fluorescent cells and reduced viability. Our results show increased membrane permeability by PEF when combined with magnetic field pulse, which can explain electroporation at considerably lower electric field strengths induced by PEMF compared to classical electroporation.
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Affiliation(s)
- Vitalij Novickij
- Vilnius Gediminas Technical University, Institute of High Magnetic Fields, Vilnius, 03227, Lithuania
| | - Audrius Grainys
- Vilnius Gediminas Technical University, Institute of High Magnetic Fields, Vilnius, 03227, Lithuania
| | - Eglė Lastauskienė
- Vilnius University, Department of Biotechnology and Microbiology, Vilnius, 03101, Lithuania
| | - Rūta Kananavičiūtė
- Vilnius University, Department of Biotechnology and Microbiology, Vilnius, 03101, Lithuania
| | - Dovilė Pamedytytė
- Vilnius University, Department of Biotechnology and Microbiology, Vilnius, 03101, Lithuania
| | - Lilija Kalėdienė
- Vilnius University, Department of Biotechnology and Microbiology, Vilnius, 03101, Lithuania
| | - Jurij Novickij
- Vilnius Gediminas Technical University, Institute of High Magnetic Fields, Vilnius, 03227, Lithuania
| | - Damijan Miklavčič
- University of Ljubljana, Faculty of Electrical Engineering, Ljubljana, SI-1000, Slovenia
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40
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Quantification of cell membrane permeability induced by monopolar and high-frequency bipolar bursts of electrical pulses. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2016; 1858:2689-2698. [PMID: 27372268 DOI: 10.1016/j.bbamem.2016.06.024] [Citation(s) in RCA: 59] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/20/2016] [Revised: 06/06/2016] [Accepted: 06/26/2016] [Indexed: 12/12/2022]
Abstract
High-frequency bipolar electric pulses have been shown to mitigate undesirable muscle contraction during irreversible electroporation (IRE) therapy. Here, we evaluate the potential applicability of such pulses for introducing exogenous molecules into cells, such as in electrochemotherapy (ECT). For this purpose we develop a method for calculating the time course of the effective permeability of an electroporated cell membrane based on real-time imaging of propidium transport into single cells that allows a quantitative comparison between different pulsing schemes. We calculate the effective permeability for several pulsed electric field treatments including trains of 100μs monopolar pulses, conventionally used in IRE and ECT, and pulse trains containing bursts or evenly-spaced 1μs bipolar pulses. We show that shorter bipolar pulses induce lower effective membrane permeability than longer monopolar pulses with equivalent treatment times. This lower efficiency can be attributed to incomplete membrane charging. Nevertheless, bipolar pulses could be used for increasing the uptake of small molecules into cells more symmetrically, but at the expense of higher applied voltages. These data indicate that high-frequency bipolar bursts of electrical pulses may be designed to electroporate cells as effectively as and more homogeneously than conventional monopolar pulses.
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Cell Monitoring and Manipulation Systems (CMMSs) based on Glass Cell-Culture Chips (GC³s). MICROMACHINES 2016; 7:mi7070106. [PMID: 30404280 PMCID: PMC6190263 DOI: 10.3390/mi7070106] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/19/2016] [Revised: 06/10/2016] [Accepted: 06/20/2016] [Indexed: 01/09/2023]
Abstract
We developed different types of glass cell-culture chips (GC3s) for culturing cells for microscopic observation in open media-containing troughs or in microfluidic structures. Platinum sensor and manipulation structures were used to monitor physiological parameters and to allocate and permeabilize cells. Electro-thermal micro pumps distributed chemical compounds in the microfluidic systems. The integrated temperature sensors showed a linear, Pt1000-like behavior. Cell adhesion and proliferation were monitored using interdigitated electrode structures (IDESs). The cell-doubling times of primary murine embryonic neuronal cells (PNCs) were determined based on the IDES capacitance-peak shifts. The electrical activity of PNC networks was detected using multi-electrode arrays (MEAs). During seeding, the cells were dielectrophoretically allocated to individual MEAs to improve network structures. MEA pads with diameters of 15, 20, 25, and 35 µm were tested. After 3 weeks, the magnitudes of the determined action potentials were highest for pads of 25 µm in diameter and did not differ when the inter-pad distances were 100 or 170 µm. Using 25-µm diameter circular oxygen electrodes, the signal currents in the cell-culture media were found to range from approximately −0.08 nA (0% O2) to −2.35 nA (21% O2). It was observed that 60-nm thick silicon nitride-sensor layers were stable potentiometric pH sensors under cell-culture conditions for periods of days. Their sensitivity between pH 5 and 9 was as high as 45 mV per pH step. We concluded that sensorized GC3s are potential animal replacement systems for purposes such as toxicity pre-screening. For example, the effect of mefloquine, a medication used to treat malaria, on the electrical activity of neuronal cells was determined in this study using a GC3 system.
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Novickij V, Grainys A, Butkus P, Tolvaišienė S, Švedienė J, Paškevičius A, Novickij J. High-frequency submicrosecond electroporator. BIOTECHNOL BIOTEC EQ 2016. [DOI: 10.1080/13102818.2016.1150792] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
Affiliation(s)
- Vitalij Novickij
- Faculty of Electronics, High Magnetic Field Institute, Vilnius Gediminas Technical University, Vilnius, Lithuania
| | - Audrius Grainys
- Faculty of Electronics, High Magnetic Field Institute, Vilnius Gediminas Technical University, Vilnius, Lithuania
| | - Paulius Butkus
- Faculty of Electronics, Department of Electrical Engineering, Vilnius Gediminas Technical University, Vilnius, Lithuania
| | - Sonata Tolvaišienė
- Faculty of Electronics, Department of Electrical Engineering, Vilnius Gediminas Technical University, Vilnius, Lithuania
| | - Jurgita Švedienė
- Laboratory of Biodeterioration Research, Nature Research Centre, Institute of Botany, Vilnius, Lithuania
| | - Algimantas Paškevičius
- Laboratory of Biodeterioration Research, Nature Research Centre, Institute of Botany, Vilnius, Lithuania
| | - Jurij Novickij
- Faculty of Electronics, High Magnetic Field Institute, Vilnius Gediminas Technical University, Vilnius, Lithuania
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Kranjc S, Kranjc M, Scancar J, Jelenc J, Sersa G, Miklavcic D. Electrochemotherapy by pulsed electromagnetic field treatment (PEMF) in mouse melanoma B16F10 in vivo. Radiol Oncol 2016; 50:39-48. [PMID: 27069448 PMCID: PMC4825331 DOI: 10.1515/raon-2016-0014] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2015] [Accepted: 01/20/2016] [Indexed: 12/21/2022] Open
Abstract
Introduction Pulsed electromagnetic field (PEMF) induces pulsed electric field, which presumably increases membrane permeabilization of the exposed cells, similar to the conventional electroporation. Thus, contactless PEMF could represent a promising approach for drug delivery. Materials and methods Noninvasive electroporation was performed by magnetic field pulse generator connected to an applicator consisting of round coil. Subcutaneous mouse B16F10 melanoma tumors were treated with intravenously injection of cisplatin (CDDP) (4 mg/kg), PEMF (480 bipolar pulses, at frequency of 80 Hz, pulse duration of 340 μs) or with the combination of both therapies (electrochemotherapy − PEMF + CDDP). Antitumor effectiveness of treatments was evaluated by tumor growth delay assay. In addition, the platinum (Pt) uptake in tumors and serum, as well as Pt bound to the DNA in the cells and Pt in the extracellular fraction were measured by inductively coupled plasma mass spectrometry. Results The antitumor effectiveness of electrochemotherapy with CDDP mediated by PEMF was comparable to the conventional electrochemotherapy with CDDP, with the induction of 2.3 days and 3.0 days tumor growth delay, respectively. The exposure of tumors to PEMF only, had no effect on tumor growth, as well as the injection of CDDP only. The antitumor effect in combined treatment was related to increased drug uptake into the electroporated tumor cells, demonstrated by increased amount of Pt bound to the DNA. Approximately 2-fold increase in cellular uptake of Pt was measured. Conclusions The obtained results in mouse melanoma model in vivo demonstrate the possible use of PEMF induced electroporation for biomedical applications, such as electrochemotherapy. The main advantages of electroporation mediated by PEMF are contactless and painless application, as well as effective electroporation compared to conventional electroporation.
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Affiliation(s)
- Simona Kranjc
- Department of Experimental Oncology, Institute of Oncology Ljubljana, Ljubljana, Slovenia
| | - Matej Kranjc
- University of Ljubljana, Faculty of Electrical Engineering
| | | | | | - Gregor Sersa
- Department of Experimental Oncology, Institute of Oncology Ljubljana, Ljubljana, Slovenia
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Electroporation Loading and Dye Transfer: A Safe and Robust Method to Probe Gap Junctional Coupling. Methods Mol Biol 2016; 1437:155-69. [PMID: 27207293 DOI: 10.1007/978-1-4939-3664-9_11] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Intercellular communication occurring via gap junction channels is considered a key mechanism for synchronizing physiological functions of cells and for the maintenance of tissue homeostasis. Gap junction channels are protein channels that are situated between neighboring cells and that provide a direct, yet selective route for the passage of small hydrophilic biomolecules and ions. Here, an electroporation method is described to load a localized area within an adherent cell monolayer with a gap junction-permeable fluorescent reporter dye. The technique results in a rapid and efficient labeling of a small patch of cells within the cell culture, without affecting cellular viability. Dynamic and quantitative information on gap junctional communication can subsequently be extracted by tracing the intercellular movement of the dye via time-lapse microscopy.
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45
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Chafai DE, Mehle A, Tilmatine A, Maouche B, Miklavčič D. Assessment of the electrochemical effects of pulsed electric fields in a biological cell suspension. Bioelectrochemistry 2015; 106:249-57. [DOI: 10.1016/j.bioelechem.2015.08.002] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2014] [Revised: 08/10/2015] [Accepted: 08/10/2015] [Indexed: 11/25/2022]
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46
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Semenov I, Zemlin C, Pakhomova ON, Xiao S, Pakhomov AG. Diffuse, non-polar electropermeabilization and reduced propidium uptake distinguish the effect of nanosecond electric pulses. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2015; 1848:2118-25. [PMID: 26112464 DOI: 10.1016/j.bbamem.2015.06.018] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/15/2015] [Revised: 05/31/2015] [Accepted: 06/15/2015] [Indexed: 12/11/2022]
Abstract
Ca2+ activation and membrane electroporation by 10-ns and 4-ms electric pulses (nsEP and msEP) were compared in rat embryonic cardiomyocytes. The lowest electric field which triggered Ca2+ transients was expectedly higher for nsEP (36 kV/cm) than for msEP (0.09 kV/cm) but the respective doses were similar (190 and 460 mJ/g). At higher intensities, both stimuli triggered prolonged firing in quiescent cells. An increase of basal Ca2+ level by >10 nM in cells with blocked voltage-gated Ca2+ channels and depleted Ca2+ depot occurred at 63 kV/cm (nsEP) or 0.14 kV/cm (msEP) and was regarded as electroporation threshold. These electric field values were at 150-230% of stimulation thresholds for both msEP and nsEP, notwithstanding a 400,000-fold difference in pulse duration. For comparable levels of electroporative Ca2+ uptake, msEP caused at least 10-fold greater uptake of propidium than nsEP, suggesting increased yield of larger pores. Electroporation by msEP started Ca2+ entry abruptly and locally at the electrode-facing poles of cell, followed by a slow diffusion to the center. In a stark contrast, nsEP evoked a "supra-electroporation" pattern of slower but spatially uniform Ca2+ entry. Thus nsEP and msEP had comparable dose efficiency, but differed profoundly in the size and localization of electropores.
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Affiliation(s)
- Iurii Semenov
- Frank Reidy Research Center for Bioelectrics, Old Dominion University, Norfolk, VA 23508, USA
| | - Christian Zemlin
- Frank Reidy Research Center for Bioelectrics, Old Dominion University, Norfolk, VA 23508, USA; Department of Electrical and Computer Engineering, Old Dominion University, Norfolk, VA 23508, USA
| | - Olga N Pakhomova
- Frank Reidy Research Center for Bioelectrics, Old Dominion University, Norfolk, VA 23508, USA
| | - Shu Xiao
- Frank Reidy Research Center for Bioelectrics, Old Dominion University, Norfolk, VA 23508, USA; Department of Electrical and Computer Engineering, Old Dominion University, Norfolk, VA 23508, USA
| | - Andrei G Pakhomov
- Frank Reidy Research Center for Bioelectrics, Old Dominion University, Norfolk, VA 23508, USA.
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Trainito C, Français O, Le Pioufle B. Analysis of pulsed electric field effects on cellular tissue with Cole–Cole model: Monitoring permeabilization under inhomogeneous electrical field with bioimpedance parameter variations. INNOV FOOD SCI EMERG 2015. [DOI: 10.1016/j.ifset.2015.02.004] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
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48
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Demiryurek Y, Nickaeen M, Zheng M, Yu M, Zahn JD, Shreiber DI, Lin H, Shan JW. Transport, resealing, and re-poration dynamics of two-pulse electroporation-mediated molecular delivery. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2015; 1848:1706-14. [PMID: 25911207 DOI: 10.1016/j.bbamem.2015.04.007] [Citation(s) in RCA: 43] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/13/2014] [Revised: 03/16/2015] [Accepted: 04/14/2015] [Indexed: 01/08/2023]
Abstract
Electroporation is of interest for many drug-delivery and gene-therapy applications. Prior studies have shown that a two-pulse-electroporation protocol consisting of a short-duration, high-voltage first pulse followed by a longer, low-voltage second pulse can increase delivery efficiency and preserve viability. In this work the effects of the field strength of the first and second pulses and the inter-pulse delay time on the delivery of two different-sized Fluorescein-Dextran (FD) conjugates are investigated. A series of two-pulse-electroporation experiments were performed on 3T3-mouse fibroblast cells, with an alternating-current first pulse to permeabilize the cell, followed by a direct-current second pulse. The protocols were rationally designed to best separate the mechanisms of permeabilization and electrophoretic transport. The results showed that the delivery of FD varied strongly with the strength of the first pulse and the size of the target molecule. The delivered FD concentration also decreased linearly with the logarithm of the inter-pulse delay. The data indicate that membrane resealing after electropermeabilization occurs rapidly, but that a non-negligible fraction of the pores can be reopened by the second pulse for delay times on the order of hundreds of seconds. The role of the second pulse is hypothesized to be more than just electrophoresis, with a minimum threshold field strength required to reopen nano-sized pores or defects remaining from the first pulse. These results suggest that membrane electroporation, sealing, and re-poration is a complex process that has both short-term and long-term components, which may in part explain the wide variation in membrane-resealing times reported in the literature.
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Affiliation(s)
- Yasir Demiryurek
- Department of Mechanical and Aerospace Engineering, Rutgers, The State University of New Jersey, 98 Brett Road, Piscataway, NJ 08854, USA
| | - Masoud Nickaeen
- Department of Mechanical and Aerospace Engineering, Rutgers, The State University of New Jersey, 98 Brett Road, Piscataway, NJ 08854, USA
| | - Mingde Zheng
- Department of Biomedical Engineering, Rutgers, The State University of New Jersey, 599 Taylor Road, Piscataway, NJ 08854, USA
| | - Miao Yu
- Department of Mechanical and Aerospace Engineering, Rutgers, The State University of New Jersey, 98 Brett Road, Piscataway, NJ 08854, USA
| | - Jeffrey D Zahn
- Department of Biomedical Engineering, Rutgers, The State University of New Jersey, 599 Taylor Road, Piscataway, NJ 08854, USA
| | - David I Shreiber
- Department of Biomedical Engineering, Rutgers, The State University of New Jersey, 599 Taylor Road, Piscataway, NJ 08854, USA
| | - Hao Lin
- Department of Mechanical and Aerospace Engineering, Rutgers, The State University of New Jersey, 98 Brett Road, Piscataway, NJ 08854, USA
| | - Jerry W Shan
- Department of Mechanical and Aerospace Engineering, Rutgers, The State University of New Jersey, 98 Brett Road, Piscataway, NJ 08854, USA.
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Sadik MM, Yu M, Zheng M, Zahn JD, Shan JW, Shreiber DI, Lin H. Scaling relationship and optimization of double-pulse electroporation. Biophys J 2014; 106:801-12. [PMID: 24559983 DOI: 10.1016/j.bpj.2013.12.045] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2013] [Revised: 09/20/2013] [Accepted: 12/31/2013] [Indexed: 02/03/2023] Open
Abstract
The efficacy of electroporation is known to vary significantly across a wide variety of biological research and clinical applications, but as of this writing, a generalized approach to simultaneously improve efficiency and maintain viability has not been available in the literature. To address that discrepancy, we here outline an approach that is based on the mapping of the scaling relationships among electroporation-mediated molecular delivery, cellular viability, and electric pulse parameters. The delivery of Fluorescein-Dextran into 3T3 mouse fibroblast cells was used as a model system. The pulse was rationally split into two sequential phases: a first precursor for permeabilization, followed by a second one for molecular delivery. Extensive data in the parameter space of the second pulse strength and duration were collected and analyzed with flow cytometry. The fluorescence intensity correlated linearly with the second pulse duration, confirming the dominant role of electrophoresis in delivery. The delivery efficiency exhibited a characteristic sigmoidal dependence on the field strength. An examination of short-term cell death using 7-Aminoactinomycin D demonstrated a convincing linear correlation with respect to the electrical energy. Based on these scaling relationships, an optimal field strength becomes identifiable. A model study was also performed, and the results were compared with the experimental data to elucidate underlying mechanisms. The comparison reveals the existence of a critical transmembrane potential above which delivery with the second pulse becomes effective. Together, these efforts establish a general route to enhance the functionality of electroporation.
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Affiliation(s)
- Mohamed M Sadik
- Department of Mechanical and Aerospace Engineering, Rutgers, The State University of New Jersey, Piscataway, New Jersey
| | - Miao Yu
- Department of Mechanical and Aerospace Engineering, Rutgers, The State University of New Jersey, Piscataway, New Jersey
| | - Mingde Zheng
- Department of Biomedical Engineering, Rutgers, The State University of New Jersey, Piscataway, New Jersey
| | - Jeffrey D Zahn
- Department of Biomedical Engineering, Rutgers, The State University of New Jersey, Piscataway, New Jersey
| | - Jerry W Shan
- Department of Mechanical and Aerospace Engineering, Rutgers, The State University of New Jersey, Piscataway, New Jersey
| | - David I Shreiber
- Department of Biomedical Engineering, Rutgers, The State University of New Jersey, Piscataway, New Jersey
| | - Hao Lin
- Department of Mechanical and Aerospace Engineering, Rutgers, The State University of New Jersey, Piscataway, New Jersey.
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Ion transport into cells exposed to monopolar and bipolar nanosecond pulses. Bioelectrochemistry 2014; 103:44-51. [PMID: 25212701 DOI: 10.1016/j.bioelechem.2014.08.015] [Citation(s) in RCA: 46] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2014] [Revised: 07/21/2014] [Accepted: 08/12/2014] [Indexed: 02/06/2023]
Abstract
Experiments with CHO cells exposed to 60 and 300 ns pulsed electric fields with amplitudes in the range from several kV/cm to tens of kV/cm showed a decrease of the uptake of calcium ions by more than an order of magnitude when, immediately after a first pulse, a second one of opposite polarity was applied. This effect is assumed to be due to the reversal of the electrophoretic transport of ions through the electroporated membrane during the second phase of the bipolar pulse. This assumption, however, is only valid if electrophoresis is the dominant transport mechanism, rather than diffusion. Comparison of calculated calcium ion currents with experimental results showed that for nanosecond pulses, electrophoresis is at least as important as diffusion. By delaying the second pulse with respect to the first one, the effect of reverse electrophoresis is reduced. Consequently, separating nanosecond pulses of opposite polarity by up to approximately hundred microseconds allows us to vary the uptake of ions from very small values to those obtained with two pulses of the same polarity. The measured calcium ion uptake obtained with bipolar pulses also allowed us to determine the membrane pore recovery time. The calculated recovery time constants are on the order of 10 μs.
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