High Intensity Electric Pulses Research Articles

Electric wind induced texturing for enhanced thermoelectric performance of p-type Mg3Sb2-based materials

High-intensity electric pulse treatment (EPT) can induce electric wind effect in materials, which facilitates the grain rearrangement and reorientation in polycrystalline samples. For the first time, this study employed the EPT technique to construct texture in Mg3.04Ag0.02Sb2 bulk compounds, and a highly conductive channel was produced to promote the charge carrier transport. This leads to a 53 % improvement in carrier mobility of the EPT sample (4#20) over the pristine one at room temperature. Additionally, EPT does not affect the carrier concentration of the material, making the EPT samples possess significantly improved electrical conductivities and untouched Seebeck coefficients. Consequently, a 36 % improvement in zT value is achieved for the EPT sample (4#20) at 723 K, compared to the pristine one. This work demonstrates that EPT technique is an effective approach for constructing textured Mg3Sb2-based materials, offering a valuable avenue for high thermoelectric performance in other potential materials via manipulating properties-related texture.

The estimation of pore size distribution of electroporated MCF-7 cell membrane

ABSTRACT The size of the pores created by external electrical pulses is important for molecule delivery into the cell. The size of pores and their distribution on the cell membrane determine the efficiency of molecule transport into the cell. There are very few studies visualizing the presence of electropores. In this study, we aimed to investigate the size distribution of electropores that were created by high intensity and short duration electrical pulses on MCF-7 cell membrane. Scanning Electron Microscopy (SEM) was used to visualize and characterize the membrane pores created by the external electric field. Structural changes on the surface of the electroporated cell membrane was observed by Atomic Force Microscopy (AFM). The size distribution of pore sizes was obtained by measuring the radius of 500 electropores. SEM imaging showed non-uniform patterning. The average radius of the electropores was 12 nm, 51.60% of pores were distributed within the range of 5 to 10 nm, and 81% of pores had radius below 15 nm. These results showed that microsecond (µs) high intensity electrical pulses cause the creation of heterogeneous nanopores on the cell membrane.

Irreversible Electroporation-Induced Inflammation Facilitates Neutrophil-Mediated Drug Delivery to Enhance Pancreatic Cancer Therapy.

Pancreatic cancer is a deadly disease with a five-year overall survival rate of around 11%. Chemotherapy is a cornerstone in the treatment of this malignancy, but the intratumoral delivery of chemotherapy drugs is impaired by the highly fibrotic tumor-associated stroma. Irreversible electroporation (IRE) is an ablative technique for treating locally advanced pancreatic cancer. During a typical IRE procedure, high-intensity electric pulses are released to kill tumor cells through the irreversible disruption of the cytoplasm membranes. IRE also induces rapid tumor infiltration by neutrophils and offers an opportunity for neutrophil-mediated drug delivery. We herein showed that the IRE-induced neutrophil trafficking was facilitated by the upregulation of neutrophil chemotaxis and migration as well as the release of several chemoattractants. Doxorubicin-loaded bovine serum albumin nanoparticles were prepared and loaded into neutrophils at a ratio of 9.9 ± 1.2 to 11.7 ± 2.0 pg of doxorubicin per cell. The resultant formulation (NP@NEs) efficiently accumulated in the IRE-treated KPC-A377 murine pancreatic tumors with an uptake value of 10.7 ± 1.5 (percent of injected dose per gram of tissue, abbreviated as %ID/g) at 48 h after intravenous injection. In both Panc02 and KPC-A377 murine pancreatic tumor models, the combination of IRE + NP@NEs inhibited tumor growth more effectively than either monotherapy. The tumors treated with the combination also exhibited the lowest frequency of Ki67+ proliferating cells and the highest abundance of terminal deoxynucleotidyl transferase dUTP nick end labeling+ (TUNEL+) apoptotic cells among the experiment groups. Minimal treatment-associated toxicity was observed. Our findings suggest that neutrophil-mediated delivery of chemotherapy drugs is a useful tool to enhance the response of pancreatic cancer to IRE.

Pulsed field ablation and ventricular capture: assessing the need for R-wave gated therapy

Abstract Background Pulsed field ablation (PFA) is a therapy that disrupts cellular homeostasis by applying high intensity and short duration electrical pulses to cardiac tissue, ultimately resulting in cell death. Such stimuli have the potential to initiate ventricular arrhythmias if the therapy is not synchronized with the beginning of ventricular systole (R-wave gating). For the treatment of cardiac arrhythmias, it is important that the candidate therapy locations in the left atrium (e.g., pulmonary veins) are a sufficient distance away from ventricular tissue to avoid ventricular capture. Objective data exploring the need for R wave gating in the context of PFA therapy for pulmonary vein isolation is currently lacking. Purpose To study the effect of electrode distance of the 12-electrode loop catheter from the epicardium on likelihood of ventricular capture. Methods A sternotomy was performed on swine to expose the heart. An incision was then made in the pericardial sac and the edges were lifted and sutured to the surrounding chest cavity to create a cradle. The function of the cradle was to hold a ∼37C saline solution (tuned to match the electrical conductivity of blood) while PFA treatments were performed. Two left ventricular sites (apex and lateral aspect) were selected for treatment, taking care to avoid proximity to the coronary artery. For each PFA therapy trial, the catheter loop was positioned 10mm above the surface of the epicardium and then advanced in 1mm increments until capture was achieved; spacers were used to assure fixed spacing during cardiac activity. For each trial, the maximum distance between the catheter and the epicardium at which the IRE therapy captured the ventricle was recorded. Additionally, CT scans (N=20 human patients) were analyzed to understand distances of interest to ventricular tissue. Results N=12 trials were conducted at each target in each animal (N=48 total ablations). For all trials, the minimum capture distance was found to be 6-8mm (4/48 at 6mm, 28/48 at 7mm and 16/48 at 8mm), with a mean capture distance of 7.25±0.60mm. The mean capture distances for the left ventricular apex and lateral aspect were 7.29±0.55mm and 7.21±0.66mm, respectively (p=0.636). For the CT scan analysis, the minimum distance from pulmonary vein ostia to left ventricular tissue ("nominal case") were 10.6mm and 12.8mm for the left superior and inferior veins, respectively. Considering the use ("worst case") where the catheter is placed just distal to the ostia, the distances to ventricular tissue were 1.6mm and 5.8mm, respectively; 4/20 patients had a vein less than 10mm from ventricular myocardium. Conclusions This study was successful in establishing the distance of ventricular capture via PFA therapy (6-8mm for the considered therapy). Given the described use and CT analysis, there is potential risk in triggering ventricular arrhythmia via PFA therapy unless R-wave triggering is implemented.

Simultaneous Delivery of Dual Inhibitors of DNA Damage Repair Sensitizes Pancreatic Cancer Response to Irreversible Electroporation.

Pancreatic ductal adenocarcinoma (PDAC) is an abysmal disease refractory to most standard therapies. Irreversible electroporation (IRE) is a local ablative technique for the clinical treatment of solid tumors, including locally advanced and unresectable PDAC, by intratumorally delivering high-intensity electric pulses to permanently disrupt cell membranes and induce cell death. But the distribution of electric field is uneven within the tumor, and in some regions, tumor cells only experience temporary perturbation to their cell membrane, a phenomenon denoted as reversible electroporation (RE). These tumor cells may survive and therefore are the main culprit of tumor relapse after IRE. We herein showed that RE, although not killing tumor cells, induced DNA double-strand breaks and activated DNA damage repair (DDR) responses. Using reactive oxygen species-sensitive polymeric micelles coloaded with Olaparib, an inhibitor of poly(ADP-ribose) polymerase (PARP), and AZD0156, an inhibitor of ataxia telangiectasia mutated (ATM), the resultant nanoformulation (M-TK-OA) disrupted both homologous recombination and nonhomologous end joining signaling of the DDR response and impaired colony formation in pancreatic cancer cells after RE. The combination of IRE and M-TK-OA significantly prolonged animal survival in both subcutaneous and orthotopic murine PDAC models and elicited CD8+ T cell-mediated antitumor immunity with a sustained antitumor memory. The efficacy of combined IRE and M-TK-OA treatments was partially attributed to the activation of cyclic GMP-AMP synthase-stimulator of interferon genes innate immune responses. Our study suggests that dual inhibition of PARP and ATM with nanomedicine is a promising strategy to enhance the pancreatic cancer response to IRE.

A single high-intensity nanosecond electric pulse stimulates NALCN and TRPC4/5 channels leading to Na+ accumulation in adrenal chromaffin cells as detected by live cell Na+ fluorescence imaging.

We recently reported that a single 5 ns high intensity electric pulse (NEP) elicits an inwardly rectifying current carried mainly by Na+ in bovine adrenal chromaffin cells, with ∼75% of the current being carried by both TRPC4/5 channels and the Na+ leak channel (NALCN) (Yang et al. Arch Biochem Biophys 723: 109252, 2022). In this study we used Na+ fluorescence imaging to further investigate the involvement of these channels in mediating Na+ influx triggered by NEPs. Chromaffin cells were loaded with the Na+ fluorescent indicator ING-2/AM (2 μM; Ex/Em: 525/545 nm; Kd = 20 mM). Similar to patch clamp experiments, a single NEP (5 MV/m) consistently evoked Na+ accumulation in all cells, which was characterized by a gradual rise in fluorescence that reached a plateau by ∼4 min. Also consistent with the inward current monitored by patch clamp, a combination of the TRPC4/5 channel inhibitor M084 (40 µM) and the NALCN blocker CP-96345 (50 µM) blocked the increase in fluorescence by ∼69%. Surprisingly, Na+ influx was significantly reduced in the absence of extracellular Ca2+ or by blocking L-type voltage-gated Ca2+ channels with nitrendipine, nifedipine or verapamil. The NEP-evoked Na+ influx pathway did not involve nicotinic agonist receptor stimulation nor voltage-gated Na+ channels. Overall, these results suggest that a 5-ns pulse triggers a Na+ conductance through NALCN and TRPC4/5 channels, serving as a novel way to modify neural cell excitability. Future experiments will identify the mechanism by which the NEP activates Na+ influx through these channels and whether these channels can also be activated by conventional electric stimulation (i.e., milli- and micro-second electric pulses).

Influence of pulsed electric field on mortality of yeasts of the genus Candida

Pulsed electric field (PEF) is a technology that uses short duration high intensity electrical pulses. Application of such a field causes electroporation of the cell membrane and consequently increases its permeability [1]. The genus Candida includes about 200 species, some of which are pathogenic to humans. These microorganisms are potentially used as a source of proteins, polysaccharides and biocomplexes in nutrition [7]. The mechanism of microbial inactivation by PEF is related to the formation of pores in the membrane, as indicated by many authors. The aim of this study is to determine the parameters of pulsed electric field affecting the lethality of selected Candida yeast strains, as well as to determine the percentage of dead cells, after PEF exposure. Depending on the voltage applied and the number of pulses, variation in yeast cell mortality is noted. In comparison with the control samples, with the increase in the number of pulses at each voltage variant, an increase in mortality among the tested yeast strains is observed.

Influence of electric field pulse on electromechanical effect in LiF crystals

Influence of electric field pulse on electromechanical effect in LiF crystals. / M. V. Galustashvili, D. G. Driaev, A. A. Iashvili, V. G. Kvatchadze, V. M. Tavkhelidze. / Nano Studies. – 2020. – # 20. – pp. 141-144. – rus. Studying of the electromechanical effect, vibrations of LiF crystal under the action of an alternating electric field, is carried out. The effect of high-intensity electric field short pulse on the crystal oscillations amplitude under the action of alternating field and its modulus of elasticity was studied. Temperature- and time-dependence of the effect after the pulse application is traced. The migration energy of defects pinning dislocations in the process of return after exposure to an electric field pulse is determined. Fig. 3, Ref. 6.

Molecular dynamics simulations of the effects of lipid oxidation on the permeability of cell membranes

The formation of transient pores in their membranes is a well-known mechanism of permeabilization of cells exposed to high-intensity electric pulses. However, the formation of such pores is not able to explain all aspects of the so-called electroporation phenomenon. In particular, the reasons for sustained permeability of cell membranes, persisting long after the pulses’ application, remain elusive. The complete resealing of cell membranes takes indeed orders of magnitude longer than the time for electropore closure as reported from molecular dynamics (MD) investigations. Lipid peroxidation has been suggested as a possible mechanism to explain the sustainable permeability of cell membranes. However, theoretical investigations of membrane lesions containing excess amounts of hydroperoxides have shown that the conductivities of such lesions were not high enough to account for the experimental measurements. Here, expanding on these studies, we investigate quantitatively the permeability of cell membrane lesions that underwent secondary oxidation. MD simulations and free energy calculations of lipid bilayers show that such lesions provide a better model of post-pulse permeable and conductive electropermeabilized cells. These results are further discussed in the context of sonoporation and ferroptosis, respectively a procedure and a phenomenon, among others, in which, alike electroporation, substantial lipid oxidation might be triggered.

Molecular Dynamics of Cell Membrane Electroporation

Electroporation is a phenomenon that can be observed when exposing biological cells to high-intensity electric pulses. The phenomenon is manifested in transient but profound increase in membrane permeability to molecules that cannot cross the membrane under physiological conditions. While electroporation is already used in many applications in medicine and biotechnology, the molecular mechanisms underlying increased cell membrane permeability continue to be an exciting research puzzle. To build the understanding of electroporation in a systematic way, it is necessary to study the biophysical responses of simplified model membrane systems. For this purpose we utilize atomistic and coarse-grained molecular dynamics simulations. We investigate how different membrane components (lipid domains) influence the formation of pores in the membrane under the influence of the electric field. Our analysis, facilitated by machine learning methods, provides interesting information on how local molecular organization governs the membrane's propensity for poration and identifies membrane properties that favor the poration event.

Paradoxical effects on voltage-gated Na+conductance in adrenal chromaffin cells by twin vs single high intensity nanosecond electric pulses.

We previously reported that a single 5 ns high intensity electric pulse (NEP) caused an E-field-dependent decrease in peak inward voltage-gated Na+ current (INa) in isolated bovine adrenal chromaffin cells. This study explored the effects of a pair of 5 ns pulses on INa recorded in the same cell type, and how varying the E-field amplitude and interval between the pulses altered its response. Regardless of the E-field strength (5 to 10 MV/m), twin NEPs having interpulse intervals ≥ than 5 s caused the inhibition of TTX-sensitive INa to approximately double relative to that produced by a single pulse. However, reducing the interval from 1 s to 10 ms between twin NEPs at E-fields of 5 and 8 MV/m but not 10 MV/m decreased the magnitude of the additive inhibitory effect by the second pulse in a pair on INa. The enhanced inhibitory effects of twin vs single NEPs on INa were not due to a shift in the voltage-dependence of steady-state activation and inactivation but were associated with a reduction in maximal Na+ conductance. Paradoxically, reducing the interval between twin NEPs at 5 or 8 MV/m but not 10 MV/m led to a progressive interval-dependent recovery of INa, which after 9 min exceeded the level of INa reached following the application of a single NEP. Disrupting lipid rafts by depleting membrane cholesterol with methyl-β-cyclodextrin enhanced the inhibitory effects of twin NEPs on INa and ablated the progressive recovery of this current at short twin pulse intervals, suggesting a complete dissociation of the inhibitory effects of twin NEPs on this current from their ability to stimulate its recovery. Our results suggest that in contrast to a single NEP, twin NEPs may influence membrane lipid rafts in a manner that enhances the trafficking of newly synthesized and/or recycling of endocytosed voltage-gated Na+ channels, thereby pointing to novel means to regulate ion channels in excitable cells.

Cisplatin and Vinorelbine -Mediated Electrochemotherapeutic Approach Against Multidrug Resistant Small Cell Lung Cancer (H69AR) In Vitro.

Small cell lung cancer (SCLC) originates from neuroendocrine branchial cells (15-20%). It is regarded as distinct from other lung cancers due to its biological and clinical features. In most cases of SCLC, surgery or radiotherapy alone is not an effective cure. The aim of our study was to examine the cytotoxic effects of chemotherapy supported by electroporation (EP) on a resistant SCLC model, in vitro. The multidrug resistant small lung cell line H69AR was used to evaluate the cytotoxic effects of cisplatin (CPPD) and vinorelbine (Navirel®; NAV) at lower doses when used with EP. Cells were treated with different concentrations of CPPD and NAV, alone or in combination with the following EP parameters: 400-1200 V/cm, 8 pulses of 100 μs duration, at 1Hz. The cell viability was estimated by MTT assay after 24 and 48 h. Apoptotic cells were detected by neutral comet assay and immunofluorescence assay with PARP-6. CPPD and NAV alone showed a dose-dependent effect on cell viability. Cytostatic drugs combined with EP revealed increased anticancer activity. Lower doses of CPPD or NAV delivered by EP were as effective as higher doses of these drugs without EP. The electrochemotherapeutic protocols increased the number of apoptotic cells and increased immunoreactivity of PARP-6. Our results indicated higher sensitivity of H69AR cells to NAV supported by EP. In SCLC cells, an increased anticancer activity was potentiated by exposure of cells to high intensity electric pulses and low drug doses. It is suggested that this method could be effectively applied in the treatment of lung cancer.

Biophysical Properties of the Electropermeabilization-Induced Membrane Conductance in Patch Clamped Adrenal Chromaffin Cells

Our group recently showed that a single 5 ns high intensity electric pulse (NEP) elicited membrane permeabilization in whole-cell voltage clamped bovine adrenal chromaffin cells, inducing an instantaneous inward conductance at the holding potential of −70 mV. When Na+ was completely replaced in the bath solution with n-methyl-d-glucamine, the NEP-induced current was significantly reduced suggesting that the current was partially carried by Na+. Later, a slow voltage ramp protocol from −100 mV to 80 mV was used to inactivate Na+ channel, whereas K+ and Ca2+ channels were blocked by cesium, tetraethylammonium and nitrendipine. With this ramp protocol, the fact that the NEP-induced conductance showed a consistent reversal potential around −10 mV revealed the properties of the current that resembled protein ion channel-like activity. We further exposed cells to SKF-96365 and La3+, both compounds considered to be able to alter the activity of TRP channels. The results showed 33% and 59 % inhibition effect on the NEP-induced current. Therefore, one possibility of the NEP-induced conductance is a TRP-like channel that is activated via some sort of elctromechnical coupling triggered as a consequence of the NEP. It is known that many TRP channels are localized in caveolae, a subset of membrane lipid rafts involved in compartmentalized signal transduction. Methy-β-cyclodextrin, as cholesterol depletion drug which disrupts caveolae integrity, produced a strong inhibitory effect on the NEP-induced current suggesting the hypothesis that caveolae disruption altered TRP trafficking and/or compartmentalization leading to a diminished ability of NEP to activate these channels, although this observation cannot rule out the possibility that membrane cholesterol depletion altered the biophysical properties of the membrane in a way that would prevent or limit the formation of lipid-containing electronanopores.

A numerical study for dielectric constant profile of aqueous solvent in ionic solution radiated by high-intensity electric pulses

In this paper, a mathematical physics model is set up to study dielectric constant profile of aqueous solvent in ionic solution, to revise Brownian dynamics simulation in ionic solution by considering time-variant dielectric constant profile with change in ion positions, and to study the effect of high-intensity electric pulses on the profile. The validation of the model is confirmed with verification calculations. By means of the proposed model, dielectric constant profiles in calcium chloride and sodium chloride solutions and their response to pulses are simulated. Based on numerical results, dielectric constants of aqueous solvent spatially vary instead of being the same value in ionic solutions. And the profiles are variant with time due to ion motion in solutions. From the profiles, overall dielectric constant in calcium chloride solution is lower than that in sodium chloride solution. And overall dielectric constant decreases with increment of solution concentration. In addition, the results show that influence on the profiles depends on solution concentration and field intensity of the pulse. The profile in solutions with low concentration is more vulnerable to the pulse than that with high concentration. And overall dielectric constant decreases dramatically as field intensity increases. Those understandings provide basis for application of pulses in biomedical engineering at the molecular level. Meanwhile, pulse radiation provides a potential way to constrain water molecules at room temperature reflected by significantly reducing dielectric constant, and to lower absorption loss of electromagnetic field in millimeter and far infrared band.

Comparative Study of Pore Formation Energy by High Intensity, Nanosecond Electrical Pulse.

Nanosecond, high intensity electric pulses create nanopores in the cell membrane. Pore formation energy is probed by taking account of the strain energy based on the continuum model. Maxwell stress acting on the cell membrane is included in the 3D model calculation as well as the effect of membrane curvature. In addition, comparison between cylindrical and toroidal pores were made to explore the difference of strain energy and force over the pores at a range of radii. Through the analyses the transmembrane potential were kept constant in order to obtain a transient response in that the electric pulse has a ultrashort duration and pore-evolving process is rapid as well. Our results demonstrate that under the same circumstances toroidal pores have higher strain energy than cylindrical pores due to the surface area and volume of the pore shape.

Ionic Conduction in Biological Nanopores Created by Ultrashort9 High-Intensity Pulses.

Ultrashort, high-intensity electric pulses open nanopores in biological cell membranes. Ion transport in nanopore is analyzed using a numerical method that couples the Nernst-Planck equations for ionic concentrations, the Poisson equation for the electric potential, and Navier-Stokes equations for the fluid flow. Roles of the applied bias, pore size, as well as the surface charge lining the membrane are comprehensively examined through I-V characteristics, conductance variations of the pore. Our results show that the surface charge distribution has an impact on the ionic conduction due to mutual electrostatic force interference. In addition, a larger pore would conduct a larger ionic current thus being more conductive on the condition of the same bias applied, which would suggest a bias-dependent expansion of pores.

Selective Electroporation of Organelles Under an Intense Picosecond Pulsed Electric Field

A high-intensity electric pulse with subnanosecond and picosecond durations may induce electroporation of an intracellular organelle while the integrity of plasma membrane in a biological cell remains intact. In this paper, selective electroporation of organelles under intense picosecond electric pulse (psEP) is theoretically studied. We construct a simplified axisymmetric model of a biological cell containing two organelles of different sizes and investigate the electroporation processes of the cell with a finite element method. The induced transmembrane voltage (TMV) and pore formation dynamics on the biological cell membrane are comparatively analyzed when the cell is exposed to sufficiently intense electric pulses of nanosecond and picosecond durations, respectively. From our results, selective electroporation of organelles can be clearly observed when the cell is affected by an intense psEP. In contrast, the electric pulse of a few hundred nanosecond duration can electroporate the plasma membrane of biological cell much before organelle membranes regardless of the magnitude of the pulse. By regulating the intensity of electric pulse with two different durations, effective pulse parameters can be obtained to realize selective electroporation of intracellular organelles or plasma membrane. Our study demonstrates the selective electroporation of organelles of intense psEP and may provide guidance for further development in experimental and theoretical research. Furthermore, the applicability of the quasi-static model used to calculate the TMV under the stimulation of a few hundred psEP is first illustrated in this paper.

Electrochemotherapy as a New Modality in Interventional Oncology: A Review.

Electroporation is a well-known phenomenon that occurs at the cell membrane when cells are exposed to high-intensity electric pulses. Depending on electric pulse amplitude and number of pulses, applied electroporation can be reversible with membrane permeability recovery or irreversible. Reversible electroporation is used to introduce drugs or genetic material into the cell without affecting cell viability. Electrochemotherapy refers to a combined treatment: electroporation and drug injection to enhance its cytotoxic effect up to 1000-fold for bleomycin. Since several years, electrochemotherapy is gaining popularity as minimally invasive oncologic treatment. The adoption of electrochemotherapy procedure in interventional oncology poses several unsolved questions, since suitable tumor histology and size as well as therapeutic efficacy still needs to be deepen. Electrochemotherapy is usually applied in palliative settings for the treatment of patients with unresectable tumors to relieve pain and ameliorate quality of life. In most cases, it is used in the treatment of advanced stages of neoplasia when radical surgical treatment is not possible (eg, due to lesion location, size, and/or number). Further, electrochemotherapy allows treating tumor nodules in the proximity of important structures like vessels and nerves as the treatment does not involve tissue heating. Overall, the safety profile of electrochemotherapy is favorable. Most of the observed adverse events are local and transient, moderate local pain, erythema, edema, and muscle contractions during electroporation. The aim of this article is to review the recent published clinical experiences of electrochemotherapy use in deep-seated tumors with particular focus on liver cases. The principle of electrochemotherapy as well as the application to cutaneous metastases is briefly described. A short insight in the treatment of bone metastases, unresectable pancreas cancer, and soft tissue sarcoma will be given. Preclinical and clinical studies on treatment efficacy with electrochemotherapy of hepatic lesions and safety of the procedure adopted are discussed.

Targeted cell membrane damage by bipolar high repeated frequency pulses

Irreversible electroporation (IRE) uses high-intensity electric pulses of ∼ 100 μs duration to induce cell death through permanent membrane destruction. In this study, monopolar pulses are replaced by bipolar high repeated frequency pulses (BHRFPs) while maintaining a constant total energized time (100 μs), burst number (90), and inter-burst delay (1 s). To observe the damage to the cell membrane directly, the fluorescent dye DiI, which has the advantages of a high signal-to-noise ratio, a lack of toxicity in cells, and slow fading, is used to label the cell membrane. This study explores the degree of damage to the stained adherent cell membrane caused by BHRFPs with equal quantities of energy. The experimental results show that the degree of damage to the cell membrane gradually increases with increasing number of bursts, but different changes are observed with different pulse widths. The DiI fluorescence intensity (degree of damage to the cell membrane) decreases from 79% to 54% with an increase in the pulse width from 400 ns (250 ×) to 10 μs (10 ×). Therefore, a positive relationship exists between the degree of cell membrane damage as we increase the pulse duration from 400 ns (250 pulses) to 10 μs (10 pulses) at the same electric field strength while delivering the same total energy. The amount of cell membrane damage increases for increasing electric field strengths with sufficiently strong fields ultimately inducing cell lysis. A numerical model of single cell is built to investigate the mechanism considering the effect of electroporation. The simulated results also show that the total pore area increases by applying the electric pulse with a pulse width of 400 ns (250 ×) to 10 μs (10 ×); an increase in the total pore area means a stronger damage degree, which agrees well with the experimental results.

Finite Element Analysis of Tissue Conductivity during High-frequency and Low-voltage Irreversible Electroporation

Introduction: Irreversible electroporation (IRE) is a process in which the membrane of the cancer cells are irreversibly damaged with the use of high-intensity electric pulses, which in turn leads to cell death. The IRE is a non-thermal way to ablate the cancer cells. This process relies on the distribution of the electric field, which affects the pulse amplitude, width, and electrical conductivity of the tissues. The present study aimed to investigate the relationship of the pulse width and intensity with the conductivity changes during the IRE using simulation. Materials and Methods: For the purpose of the study, the COMSOL 5 software was utilized to predict the conductivity changes during the IRE. We used 4,000 bipolar and monopolar pulses with the frequency of 5 kHz and 1 Hz, width of 100 µs, and electric fields of low and high intensity. Subsequently, we built three-dimensional numerical models for the liver tissue. Results: The results of our study revealed that the conductivity of tissue increased during the application of electrical pulses. Additionally, the conductivity changes increased with the elevation of the electric field intensity. Conclusion: As the finding of this study indicated, the IRE with high-frequency and low electric field intensity could change the tissue conductivity. Therefore, the IRE was recommended to be applied with high frequency and low voltage.