Cell Membrane Electroporation Research Articles

Improving the lipid extraction yield from Chlorella based on the controllable electroporation of cell membrane by pulsed electric field

In order to solve the increasingly serious problems of energy and environment, microalgae are used as a raw material for extracting lipids to produce biodiesel. Prior to the extraction of lipids, microalgae were treated with high-voltage pulsed electric field (PEF) to break the cell membrane. It was found that the lipid extraction yield depends on the electric field strength (E) and the specific energy input (Wsp), and has a certain relationship with the cell disintegration rate of Chlorella. The perforation degree of the Chlorella's cell membrane by PEF treatment is controllable, moderate perforation can be ensured by controlling the power parameters. PEF treatment significantly improved the extraction yield of lipids. Compared with the test samples without PEF treatment, PEF treatment increased the lipid extraction yields by up to 166.67%. However, an excessively high voltage will cause the quality of the extracted biodiesel to decrease.

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.

Resistor–capacitor modeling of the cell membrane: A multiphysics analysis

In this Tutorial, we provide a discussion of “What are cell membrane resistance (MR) and capacitance (MC)?” and then give a number of examples to illustrate how cell membranes constitute nature's ultimate stretchable resistor–capacitor network. There are many approaches to the analysis of the electric field effects in cell membranes, but a particularly intuitive and conceptually straightforward method is to use the biophysically inspired lumped parameter resistor (R)–capacitor (C) network in order to simulate the charging and discharging processes. By developing advanced multiphysics and multiscale numerical analysis, we expect to learn many cross-properties of biological materials which involve multiple spatial or temporal scales. These include electrodeformation (ED) and electroporation (EP) biophysical processes occurring in the cell membrane. In a first stage, we present electric and mechanical circuit analog models of cell membranes and examine their predictions and limitations. An important parameter that researchers can tune with these deterministic approaches is the strength of the transmembrane voltage Vm: at low values of Vm, MC varies quadratically as a function of Vm and MR is infinite, but as Vm is increased at a value below the EP threshold, the membrane should be considered as a nonlinear capacitor. Over the EP threshold, there is a decrease in Vm and MR due to the charge transport across the membrane. Mechanical and electrical stresses, singly or in combination, can result in damage and eventually breakdown of the membrane. In a second stage, the parameters in the finite element (FE) modeling that we present are linked to scales we know should be associated with EP and ED processes. We present simulation data and attempt to determine whether the MC and MR behaviors compare well with experimental observations and/or trends from analytical approaches. MC and MR are correlated with the dielectric, mechanical, and morphological information of cells. For an initially spherical cell exposed to an electric field, monitoring MC and MR reflects a quadratic and then higher order nonlinear behavior as a function of Vm. The quadratic regime scales with spheroidal morphologies of the stressed cell up to a critical value of Vm beyond which higher order nonlinearities arise, and the cell shape is no longer described by a spheroid. Furthermore, we consider the present challenges of connecting electrostatic stress, strain energy in multi-cellular environments to sub-cellular scale material properties, and show that they have the potential to explain the ED and EP of cell membranes via multi-physics and multi-scale numerical analysis. The emergence of Vm as a reporter of neighboring cell interactions is also discussed in a theory-based method for constructing realistic models of tissues based on densely packed environments made by irregularly shaped cells. Of particular interest is the proximity-induced ED and capacitive coupling between neighboring cells, and the subsequent correlation that this has upon anisotropic local ED distribution over a wide range of conditions. For future studies, we identify significant challenges, opportunities, and a sampling of a few used case studies for the development of tissue ED and EP modeling in the coming years.

Pulsed field ablation: a promise that came true.

Pulsed field ablation is a nonthermal ablative modality that uses short living, strong electrical field created around catheter to create microscopic pores in cell membranes (electroporation). When adequately dosed/configured it shows a preference for myocardial tissue necrosis. Thus, it holds a promise to become a 'perfect' energy source for cardiac ablation to treat arrhythmias. Herein, we present update on platforms in clinical development. First in human series using pulsed field ablation for atrial fibrillation ablation have been completed and data published for several platforms. Acute safety outcomes are similar across the platforms with exceptionally low rate of those complications that are typically reported for thermal ablation methods (esophageal injury, pulmonary vein stenosis, phrenic nerve palsy). Promising acute data on pulmonary vein isolation had been corroborated with satisfactory 1-year clinical follow-up for a single platform, whereas reports are pending for the rest. Research efforts are being expanded to a development of focal catheters, and therefore, pulsed field ablation application for ventricular arrhythmias. As the reports confirming its safety and efficacy build up, there seems to be no way that the promise of pulsed field ablation could end in a blind alley.

Field enhancement in microfluidic semiconductor nanowire array.

Nano-material integrated microfluidic platforms are increasingly being considered to accelerate biological sample preparation and molecular diagnostics. A major challenge in this context is the generation of high electric fields for electroporation of cell membranes. In this paper, we have studied a novel mechanism of generating a high electric field in the microfluidic channels by using an array of semiconductor nanowires. When an electrostatic field is applied across a semiconductor nanowire array, the electric field is localized near the nanowires and the field strength is higher than what was reported previously with various other micro-geometries. Nanowires made of ZnO, Si, and Si-SiO2 and their orientation and array spacing are considered design parameters. It is observed that for a given ratio of the spacing between nanowires to the diameter, the electric field enhancement near the edges of ZnO nanowires is nearly 30 times higher compared to Si or Si-SiO2 nanowire arrays. This enhancement is a combined effect of the unique geometry with a pointed tip with a hexagonal cross section, the piezoelectric and the spontaneous polarization in the ZnO nanowires, and the electro-kinetics of the interface fluid. Considering the field localization phenomena, the trajectories of E. coli cells in the channel are analyzed. For a given inter-nanowire spacing and an applied electric field, the channels with ZnO nanowire arrays have a greater probability of cell lysis in comparison to Si-based nanowire arrays. Detailed correlations between the cell lysis probability with the inter-nanowire spacing and the applied electric field are reported.

Dye Transport through Bilayers Agrees with Lipid Electropore Molecular Dynamics

Although transport of molecules into cells via electroporation is a common biomedical procedure, its protocols are often based on trial and error. Despite a long history of theoretical effort, the underlying mechanisms of cell membrane electroporation are not sufficiently elucidated, in part, because of the number of independent fitting parameters needed to link theory to experiment. Here, we ask if the electroporation behavior of a reduced cell membrane is consistent with time-resolved, atomistic, molecular dynamics (MD) simulations of phospholipid bilayers responding to electric fields. To avoid solvent and tension effects, giant unilamellar vesicles (GUVs) were used, and transport kinetics were measured by the entry of the impermeant fluorescent dye calcein. Because the timescale of electrical pulses needed to restructure bilayers into pores is much shorter than the time resolution of current techniques for membrane transport kinetics measurements, the lifetimes of lipid bilayer electropores were measured using systematic variation of the initial MD simulation conditions, whereas GUV transport kinetics were detected in response to a nanosecond timescale variation in the applied electric pulse lifetimes and interpulse intervals. Molecular transport after GUV permeabilization induced by multiple pulses is additive for interpulse intervals as short as 50 ns but not 5-ns intervals, consistent with the 10–50-ns lifetimes of electropores in MD simulations. Although the results were mostly consistent between GUV and MD simulations, the kinetics of ultrashort, electric-field-induced permeabilization of GUVs were significantly different from published results in cells exposed to ultrashort (6 and 2 ns) electric fields, suggesting that cellular electroporation involves additional structures and processes.

Intraoperative electrochemotherapy in locally advanced pancreatic cancer: Results and impact on quality of life. a single center experience.

e16731 Background: Locally advanced pancreatic cancer (LAPC) is usually treated with chemoradiotherapy with poor results, thus additional therapies have been proposed. Of the latter, electrochemotherapy (ECT) represents a non-thermal ablation method, which combines the administration of chemotherapeutic drugs with permeabilizing electric pulses for cell membrane electroporation. The present study is the first to assess the short and long-term results, and the quality of life of the patients who underwent ECT for LAPC. Methods: Observational study of patients affected by LAPC who underwent intraoperative ECT after chemoradiotherapy. The inclusion criteria were: 1- patients with LAPC (defined according to the National Comprehensive Cancer Network 2019), 2- previous chemoradiotherapy and 3- absence of disease progression at restaging. Data at diagnosis and at restaging were collected for each patient. The Quality of life was evaluated using the Euro Quality of Life Group Association Questionnaire (EQ-5D-5L). The questionnaire was administered to all patients before and after ECT. Results: From May 25, 2018 to November 26, 2019 five patients underwent ECT: in 4 cases, the tumors were located in the head and, in one, in the body of the pancreas. Preoperative chemotherapy consisted mainly of 6 cycles of modified folfirinox, while the radiotherapy consisted of 54 Gy (27 fractions). At restaging, the serum value of CA 19-9 and tumor size were reduced; however, the vascular involvement did not change. No downstaging was recorded. Intravenous bleomycin 15,000IU/m2 was given as a bolus, the ECT procedure was performed using at least 4 needles with a mean duration time of 27 minutes, (range 15-40). No postoperative mortality or major complications were reported. The mean length of stay was 8 days (range 5-14). Four patients were alive and well at the end of the study while one patient died from disease progression. The mean follow-up was 20.8 months (range 9-34) from diagnosis and 9.4 months (range 2-19) from ECT. The quality of life was good (EQ-5D-5L scale > 50 in all cases) and there was improvement in pain/discomfort with respect to the pre-treatment period in 3 out of 5 patients. Conclusions: Electrochemotherapy can be considered a simple, feasible and safe palliative additional treatment in LAPC without progression after chemoradiotherapy, and it seems to allow a good quality of life and pain improvement.

The Effect of KcsA Channel on Lipid Bilayer Electroporation Induced by Picosecond Pulse Trains.

Membrane proteins are the major component of plasma membranes, and they play crucial roles in all organisms. To understand the influence of the presence of KcsA channel on cell membrane electroporation induced by picosecond pulse trains (psPT), in this paper, the electroporation of KcsA membrane protein system and bare lipid bilayer system (POPC) with the applied psPT are simulated using molecular dynamics (MD) method. First, we find that the average pore formation time of the KcsA system is longer than the bare system with the applied psPT. In the KcsA system, water protrusions appear more slowly. Then, the system size effects of psPT in the MD simulations are investigated. When the system size decreases, the average pore formation time of small KcsA membrane protein system is shorter than the bare system with the applied psPT. It is found that the psPT makes the protein fluctuation of small system increase greatly; meanwhile the instability of protein disturbs the water and then affects the water protrusion appearance time. Furthermore, it shows that the protein fluctuation of constant electric field is smaller than that of psPT and no field, and protein fluctuation increases with the psPT repetition frequency increasing.

Asymmetric voltage multiplying circuit coupled to sliding electrodes for biomass fractionation with high-voltage and high current pulsed electric fields

Pulsed electric field (PEF) is an emerging technology for biomass processing and fractionation by electroporation of cell membrane. Nevertheless, PEF technology and devices require tailoring and adaptation for each specific type of biomass. Such an optimization requires convenient and adaptable laboratory systems, which will enable both electrical and mechanical parameters determination before process upscaling. In this work, we report on the design and development of a laboratory PEF system that allows applying for up to 4[Formula: see text]kV, 1[Formula: see text]kA pulses with 1–100[Formula: see text][Formula: see text]s and total power dissipation of 20[Formula: see text]W and up to 25[Formula: see text]kg of mechanical load. The design of an asymmetric voltage multiplying circuit allows for controlling pulse parameters for each pulse in series. Such an approach enables precise adaptation of PEF to the changing conductivity of the biomass, minimizing the total invested energy in the process. The system was tested on highly conductive marine macroalgae Ulva sp, a promising but challenging feedstock for the biorefinery. This work provides a design of an adaptable PEF device, important for biomass processing with electroporation.

On the possible mechanisms of the selective effect of a non‐equilibrium plasma on healthy and cancer cells in a physiological solution

This paper discusses possible mechanisms for the selective effect of weakly ionized nonequilibrium plasma and currents in electrolytes on healthy and cancerous cells in physiological saline in a Petri dish. The interaction with the plasma source leads to a change in osmotic pressure, which affects the electro-mechanical properties of cell membranes in healthy and cancerous cells in different ways. The currents arising in the electrolyte charge the membranes of healthy and cancerous cells to a different potential difference due to the different values of the membranes’ dielectric constants. We hypothesized: 1. The dielectric permeability of cancer cell membranes is lower than that of healthy cells, as is the capacity of a unit of the membrane surface, and therefore, the additional potential difference acquired by the membrane through charging with currents induced in the intercellular electrolyte is greater in cancer cells. This can lead to electroporation of cancer cell membranes, resulting in their apoptosis, but does not affect healthy cells. 2. It is known from the literature that the equilibrium potential differences on the membrane (resting potential) of cancer and healthy cells are noticeably different. Therefore, a change in the potential difference on the membrane due to currents in the extracellular fluid can affect the permeability and transport properties of the membranes. It can also be a reason for the selective effect of the nonequilibrium plasma interaction with healthy and cancerous cells in physiological saline.

Cancellation of nerve excitation by the reversal of nanosecond stimulus polarity and its relevance to the gating time of sodium channels.

The initiation of action potentials (APs) by membrane depolarization occurs after a brief vulnerability period, during which excitation can be abolished by the reversal of the stimulus polarity. This vulnerability period is determined by the time needed for gating of voltage-gated sodium channels (VGSC). We compared nerve excitation by ultra-short uni- and bipolar stimuli to define the time frame of bipolar cancellation and of AP initiation. Propagating APs in isolated frog sciatic nerve were elicited by cathodic pulses (200ns-300µs), followed by an anodic (canceling) pulse of the same duration after a 0-200-µs delay. We found that the earliest and the latest boundaries for opening the critical number of VGSC needed to initiate AP are, respectively, between 11 and 20µs and between 100 and 200µs after the onset of depolarization. Stronger depolarization accelerated AP initiation, apparently due to faster VGSC opening, but not beyond the 11-µs limit. Bipolar cancellation was augmented by reducing pulse duration, shortening the delay between pulses, decreasing the amplitude of the cathodic pulse, and increasing the amplitude of the anodic one. Some of these characteristics contrasted the bipolar cancellation of cell membrane electroporation (Pakhomov et al. in Bioelectrochemistry 122:123-133, 2018; Gianulis et al. in Bioelectrochemistry 119:10-19, 2017), suggesting different mechanisms. The ratio of nerve excitation thresholds for a unipolar cathodic pulse and a symmetrical bipolar pulse increased as a power function as the pulse duration decreased, in remarkable agreement with the predictions of SENN model of nerve excitation (Reilly and Diamant in Health Phys 83(3):356-365, 2002).

IGBT-Based Pulsed Electric Fields Generator for Disinfection: Design and In Vitro Studies on Pseudomonas aeruginosa.

Irreversible electroporation of cell membrane with pulsed electric fields is an emerging physical method for disinfection that aims to reduce the doses and volumes of used antibiotics for wound healing. Here we report on the design of the IGBT-based pulsed electric field generator that enabled eradication of multidrug resistant Pseudomonas aeruginosa PAO1 on the gel. Using a concentric electric configuration we determined that the lower threshold of the electric field required to kill P. aeruginosa PAO1 was 89.28 ± 12.89Vmm-1, when 200 square pulses of 300µs duration are delivered at 3Hz. These parameters disinfected 38.14 ± 0.79mm2 area around the single needle electrode. This study provides a step towards the design of equipment required for multidrug-resistant bacteria disinfection in patients with pulsed electric fields.

Effects of Pulsed Electric Field Treatment on Compression Properties and Solutes Diffusion Behaviors of Jerusalem artichoke.

Jerusalem artichoke is widely used as raw material for industrial production of inulin. Pressing (compression) and diffusion are two effective technologies for bio-compounds’ recovery from plants. In this work, pulsed electric field (PEF) treatment at 400, 600, and 800 V/cm during 100 ms was applied to facilitate juice and solutes recovery from Jerusalem artichoke. The application of PEF led to electroporation of cell membranes and enhanced the tissue compression/juice expression and solutes diffusion. The consolidation coefficient (calculated by application of semi-empirical model) of PEF treated sample at 800 V/cm was 6.50 × 10−7 m2/s, which is significantly higher than that of untreated sample (5.02 × 10−9 m2/s) and close to that of freeze-thawed sample. Diffusion experiments with PEF treated samples were carried out at 25, 50, and 75 °C. A PEF treatment of Jerusalem artichoke at 800 V/cm led to a similar diffusion behavior at 25 °C, compared to diffusion behavior obtained from untreated sample at 75 °C.

Excitation of murine cardiac myocytes by nanosecond pulsed electric field.

Opening of voltage-gated sodium channels takes tens to hundreds of microseconds, and mechanisms of their opening by nanosecond pulsed electric field (nsPEF) stimuli remain elusive. This study was aimed at uncovering the mechanisms of how nsPEF elicits action potentials (APs) in cardiomyocytes. Fluorescent imaging of optical APs (FluoVolt) and Ca2+ -transients (Fluo-4) was performed in enzymatically isolated murine ventricular cardiomyocytes stimulated by 200-nanosecond trapezoidal pulses. nsPEF stimulation evoked tetrodotoxin-sensitive APs accompanied or preceded by slow sustained depolarization (SSD) and, in most cells, by transient afterdepolarization waves. SSD threshold was lower than the AP threshold (1.26 ± 0.03 vs 1.34 ± 0.03 kV/cm, respectively, P < 0.001). Inhibition of l-type calcium and sodium-calcium exchanger currents reduced the SSD amplitude and increased the AP threshold ( P < 0.05). The threshold for Ca 2+ -transients (1.40 ± 0.04 kV/cm) was not significantly affected by a tetrodotoxin-verapamil cocktail, suggesting the activation of a Ca 2+ entry pathway independent from the opening of Na + or Ca 2+ voltage-gated channels. Removal of external Ca 2+ decreased the SSD amplitude ( P = 0.004) and blocked Ca 2+ -transients but not APs. The incidence of transient afterdepolarization waves was decreased by verapamil and by removal of external Ca 2+ ( P = 0.002). The study established that nsPEF stimulation caused calcium entry into cardiac myocytes (including routes other than voltage-gated calcium channels) and SSD. Tetrodotoxin-sensitive APs were mediated by SSD, whose amplitude depended on the calcium entry. Plasma membrane electroporation was the most likely primary mechanism of SSD with additional contribution from l-type calcium and sodium-calcium exchanger currents.

Electrochemotherapy in head and neck cancer: A review of an emerging cancer treatment.

Patients affected by aggressive neoplasms with a high propensity to metastasize to the skin, including some types of head and neck cancer, may benefit from electrochemotherapy, a modality that combines the electroporation of cell membranes and chemotherapy to facilitate the transport of non-permeant molecules into cells; the host immune response consequently participates in achieving the abolition of tumors. Electrochemotherapy can be successfully used for skin metastases of head and neck tumors and, with some limitations, for primary and relapsing neoplasms; it can also be applied on an outpatient basis with a favorable cost-benefit ratio and it is a repeatable treatment that, if necessary, can be followed by traditional antineoplastic therapies. Although still a palliative treatment, the good level of tolerability and the high success rates of electrochemotherapy make it worth consideration among treatment options in selected patients.

MODELLING AND ANALYSIS OF ELECTROPORATION PARAMETERS OF THE MEMBRANE OF A BIOLOGICAL CELL IN A VARIED INTENSITY PULSED ELECTRIC FIELD

Context. The problem of constructing electroporation models for membranes of biological cells by the methods of nonlinear approximation using the experimental dependences of their specific electric conductivity on intensity pulsed electric field was solved in the paper.Objective is a construction of models, which adequately describe the experimentally obtained nonlinear effects of the conductivity of the cell, including reversible electroporation, irreversible electrical breakdown or local reversible electrical breakdown of membranes at the fusion of two contacting cells.Method. Polynomials of 8–10 degrees are chosen as the functions that modelling the experimental ones and the criteria for estimating the parameters of electroporation are the coordinates of the local extrema of their curvature and inflexion points that characterize the specified state of the cell membrane at current field intensity. The approximation problem was solved by the least squares method. The calculation of the estimate of the polynomials coefficients was carried out by the Gaussian elimination – the forward and reverse moves were realized. It is possible to search for extrema of the obtained polynomials of high degrees by specifying a calculation error. The root-mean-square error of the approximation is used for finding the degree of the polynomial. The current curvature of the polynomial is counted by calculating the first and second order derivatives of conductivity. The values of the curvature, which obtained via these methods, make possible to determine the inflexion points of the curve for purpose to determine breakdown of a cell membrane.Results. Applied software was developed, polynomial models of the conductivity of a biological cell in a varied intensity pulsed electric field were constructed and their quantitative mathematical analysis was carried out by using this software. All these calculations are proved by graphs, some of which can be viewed on an enlarged scale.Conclusions. The parameters of electroporation of a biological cell membrane obtained by analysing the curvature function of polynomial models are calculated. The developed analytical methods and software for determining the parameters of electroporation allow us to recommend them for use in practice in calculating the numerical values of the field intensity and conductivity at which specific electroporation regimes of the biological cell membrane are provided.

Low field MRI study of the potato cell membrane electroporation by pulsed electric field

The effects of high voltage pulsed electric fields (PEF) applied to potato tubers were examined by the contrast enhanced, low field Magnetic Resonance Imaging (MRI). This is a non-destructive, and relatively inexpensive method that allows to monitor the spatial distribution of damages caused by the pulses and their evolution in time. The MRI results confirmed the irreversible damage of the potato tuber cell membranes caused by the PEF treatment, leading to non-selective flow of ions. The extent of electroporation was also evaluated by electrical conductivity measurements, as well as by compression tests and compared with the MRI. On the basis of these results, the PEF method can be optimized in applications aiming at the increase of the permeability of potato cell membranes.

Safety and feasibility of electrochemotherapy in patients with unresectable colorectal liver metastases: A pilot study

Background and objectivesElectrochemotherapy is a novel ablation technique combining chemotherapeutic agents with reversible cell membrane electroporation. Previous experiences have shown its efficacy for cutaneous tumors. Its application for deep-seated malignancies is under investigation. We performed a prospective, pilot study to evaluate the feasibility, safety, and efficacy of intraoperative electrochemotherapy for otherwise unresectable colorectal liver metastases. MethodsElectrochemotherapy with bleomycin was combined with open liver resection and performed with linear or hexagonal needle electrodes according to an individualized pretreatment plan. The primary endpoints were: feasibility, as ratio of completed to planned treatments; safety, and efficacy, as per response assessed at 30 days with MRI and according to RECIST. The secondary endpoint was overall and progression-free survival at month 6. ResultsA total of 9 colorectal liver metastases were treated in 5 patients with 20 electrode applications. No intraoperative complications were observed. At day 30, complete response was 55.5% and stable disease 45.5%. All (5) patients reached a 6 months overall survival, and 4 out of 5 patients had 6 months progression free survival. ConclusionsElectrochemotherapy is a feasible and safe adjunct to open surgery for treatment of unresectable colorectal liver metastases. Larger studies and longer follow-ups are favored to better define its role in the treatment of secondary liver malignancies.

Voltage Charging Gold-Microtube Membranes for Electroporation

Electroporation of cell membrane occurs when sufficiently large electric field gradients (in the order of kV/cm) are applied to a cell medium. This is routinely accomplished in medicine and biology using voltage pulses above 1 kV in order to incorporate foreign molecules and genes into living cells.1 However, transient pore formation or reversible electroporation is a challenge with such large voltages because of Joule heating, pH changes and ion dissolution that lead to high cell mortality.2 Furthermore, special safety precautions are required. As such, the miniaturization of electroporation devices has been a research interest in order to reach similar electric field gradients with lower voltages.3 It was also shown that these microscopic devices result in higher electroporation yields and better cell viability, although often reducing the cell throughput. We have developed an electroporation system that consists on charging gold microtubes inside a filter membrane to electroporate Escherichia coli at low voltages (<5 V).4 Supporting our experimental results with theoretical simulations, we have shown that electric field gradients of 4 kV/cm, sufficiently large to reversibly porate the bacteria membrane, were formed inside the gold microtubes. Following the incorporation of exogenous probes inside E. coli with fluorescence microscopy and spectroscopy, we have determined that up to 40% of the bacteria were reversibly electroporated. This is more than an order of magnitude higher than the efficiency obtained with a commercial electroporation device. Finally, cell throughput of >30 million cells per minutes, higher than any previously reported device, were obtained. Gehl, J. Acta Physiol. Scand. 2003, 177, 437-447.Lee, W. G.; Demirci, U.; Khademhosseini, A. Integr. Biol. 2009, 1, 242-251.Geng, T.; Lu, C. Lab Chip 2013, 13, 3803-3821.Experton, J.; Wilson, A. G.; Martin C. R. Anal. Chem. [Article ASAP]. DOI: 10.1021/acs.analchem.6b03820. Published Online: Nov 17, 2016.

Effect of Thermal Gradients Created by Electromagnetic Fields on Cell-Membrane Electroporation Probed by Molecular-Dynamics Simulations

Pulses of high electric fields increase cell-membrane permeability, and this $e\phantom{\rule{0}{0ex}}l\phantom{\rule{0}{0ex}}e\phantom{\rule{0}{0ex}}c\phantom{\rule{0}{0ex}}t\phantom{\rule{0}{0ex}}r\phantom{\rule{0}{0ex}}o\phantom{\rule{0}{0ex}}p\phantom{\rule{0}{0ex}}o\phantom{\rule{0}{0ex}}r\phantom{\rule{0}{0ex}}a\phantom{\rule{0}{0ex}}t\phantom{\rule{0}{0ex}}i\phantom{\rule{0}{0ex}}o\phantom{\rule{0}{0ex}}n$ can be used to introduce drugs or other molecules into cells, to trigger intracellular calcium release, or to shrink tumors, for example. Electroporation by nanosecond pulsed fields has been considered a nonthermal process, but huge temperature gradients could arise at the membrane, and the authors' molecular dynamics simulations suggest an important role of these gradients in directing and enhancing biophysical responses.