External Electric Field Pulses Research Articles

Effects of buffer composition and plasmid toxicity on electroporation-based non-viral gene delivery in mammalian cells using bursts of nanosecond and microsecond pulses.

Gene electrotransfer (GET) is non-viral gene delivery technique, also known as electroporation-mediated gene delivery or electrotransfection. GET is a method used to introduce foreign genetic material (such as DNA or RNA) into cells by applying external pulsed electric fields (PEFs) to create temporary pores in the cell membrane. This study was undertaken to examine the impact of buffer composition on the efficiency of GET in mammalian cells Also, we specifically compared the effectiveness of high-frequency nanosecond (ns) pulses with standard microsecond (µs) pulses. For the assessment of cell transfection efficiency and viability, flow cytometric analysis, luminescent assays, and measurements of metabolic activity were conducted. The efficiency of electrotransfection was evaluated using two different proteins encoding plasmids (pEGFP-N1 and Luciferase-pcDNA3). The investigation revealed that the composition of the electroporation buffer significantly influences the efficacy of GET in CHO-K1 cell line. The different susceptibility of cell lines to the electric field and the plasmid cytotoxicity were reported. It was also shown that electroporation with nanosecond duration PEF protocols ensured equivalent or even better transfection efficiency than standard µsPEF. Additionally, we successfully performed long-term transfection of the murine 4T1 cell line using high-frequency nanosecond PEFs and confirmed its' applicability in an in vivo model. The findings from the study can be applied to optimize electrotransfection conditions.

Impact of supercooling storage on physical and chemical properties of yellowfin tuna (Thunnus albacares)

Seafood is highly perishable, and its spoilage begins immediately after harvesting due to the production of various metabolites. However, freezing, a conventional long-term preservation technology, causes quality degradation due to ice crystallization. Supercooling has emerged as a promising technique to prevent ice formation and quality degradation. In this study, tuna fillets were supercooled at −3.5 °C with an external pulsed electric field (PEF) and oscillating magnetic field (OMF) strengths for optimization. Quality factors such as drip loss, color, microbial analysis, texture, and total volatile basic nitrogen (TVB-N) were evaluated in comparison with refrigerated, frozen-thawed, and supercooled samples stored for 1, 4, 7, and 10 days. The results showed that supercooled samples had lower TVB-N values than refrigerated samples. The aerobic plate counts of supercooled tuna samples did not significantly vary from 1 to 7 days of storage. Moreover, supercooling preserved the textural integrity of the product and reduced drip loss compared to frozen-thawed samples. Therefore, supercooling preservation can extend the shelf-life of tuna fillets while minimizing quality degradation, indicating its potential compared to conventional refrigeration and freezing methods.

Enhancement of a pyroelectric body energy harvesting scheme employing pulsed electric fields.

This research utilizes waste heat energy as a sustainable energy source to enhance pyroelectric power output by combining pyroelectric nanogenerators with an external pulsed electric field. When the surface temperature of the pyroelectric body varies, applying different pulses of the external electric field results in maximum power accumulation. A novel power-generating experimental setup was developed to measure and compute pyroelectric power generation. A standard Fuji ceramic C-9 sample was used to generate pyroelectric energy in a 20 °C temperature range from 120 to 140 °C. The continuous temperature variation frequency was 0.05Hz, and the pulsed electric field was applied when the temperature rose. Pulses of the electric field with widths of 10, 50, 100, and 200ms were applied to the sample under different pulse amplitudes, and the amplitude of each pulse was 250, 500, 1000, or 1500 V/mm. The maximum power generated through the application of an external pulsed electric field under the above-mentioned conditions was evaluated. This system had the highest power density of 0.204 mJ cm-2 °C-1kV-1. In addition, for the lowest input power, the maximum power generation condition was a 10ms pulse width and an amplitude of 250Vmm-1 in the applied electric field. This state might power smart sensor modules, IoT devices, automobiles, and other waste heat energy applications. Nano-pulse electric field applications may reduce input power to its lowest level, dependent on net-producing power. Therefore, new researchers can use net-generation power efficiency to create a large-scale power source using multiple pyroelectric arrays.

Large amplitude density fluctuations in a lipid bilayer, induced by picosecond electric pulses, and their possible biotechnological applications

Electroporation refers to changes in permeabilization of lipid membranes induced by external pulsed electric fields. Diverse applications of electroporation in biotechnology include gene transfer, modulation of gene expression, cell proliferation, seed germination, sterilization in the food industry, and extraction of chemical compounds. We argue that the formation of large amplitude, subnanometer density fluctuations in lipid bilayers, induced by high-intensity pulsed electric fields with picosecond durations, may produce lipid nanopores and change transmembrane transport, which trigger cellular signalling pathways with subsequent cellular responses and changes in cell physiology, thus, could represent perspectives regarding the development of electroporation biotechnologies.

Angle selective piezoelectric strain-controlled magnetization switching in artificial spin ice based multiferroic system

The prospect of electrically controlled writing of ferromagnetic bits is highly desirable for developing scalable and energy-efficient spintronics devices. In this direction, various efforts have been made to achieve electrically controlled magnetization switching utilizing an artificial multiferroic system. To date, the magnetization switching has been realized in a diverse nanopatterned magnetic system. However, the demonstration of electric field-induced strain-controlled magnetization switching in artificial spin ice (ASI) coupled with a piezoelectric material is still unexplored. In the present work, we perform micromagnetic simulations to investigate the electric field-induced strain-mediated magnetization switching in an ASI based multiferroic system. Here, the piezoelectric strain-controlled magnetization switching has been studied by applying the electric-field pulse at different angles with respect to the axes of the system. Remarkably, magnetization switches by 180° only if the external electric-field pulse is applied at some specific angles, close to the anisotropy axis of the system (≈30°–60°). Our detailed analysis of the demagnetization energy variation reveals that the energy barrier becomes antisymmetric in such cases, facilitating complete magnetization reversal. Moreover, we have also proposed a possible magnetization reversal mechanism with two sequential electric-field pulses of a relatively smaller magnitude. We believe that the present work could pave the way for a future ASI-based multiferroic system for scalable magnetic field-free low power spintronics devices.

Study of the piezoelectric properties of rubidium acid phthalate crystals by time-resolved three-crystal X--ray diffractometry

Using the method of time-resolved X-ray diffractometry in a three-crystal scheme, the lattice deformation of a rubidium biphthalate (C8H5RbO4) crystal was measured in an external electric field. Under the action of an external pulsed electric field along the [001] polar direction, the piezoelectric moduli d31,d32, and d33 were determined independently using three reflections 400, 070, and 004; the obtaind values are -32.8±0.6, 12.8±0.3, and 21.8±1.2 pC/N, respectively. A good agreement was found between the values of the piezoelectric moduli obtained in this work and the values obtained earlier by the quasi-static method. Keywords: piezoelectric effect, time-resolved X-ray diffractometry, three-crystal diffraction scheme, acid phthalate crystals, external electric field.

Исследование пьезоэлектрических свойств кристаллов бифталата рубидия методом времяразрешающей трехкристальной рентгеновской дифрактометрии

Using the method of time-resolved X-ray diffractometry in a three-crystal scheme, the lattice deformation of a rubidium biphthalate (С8H5RbO4) crystal was measured in an external electric field. Under the action of an external pulsed electric field along the [001] polar direction, the piezoelectric moduli d31, d32, and d33 were determined independently using three reflections 400, 070, and 004; the obtaind values are –32.8 ± 0.6, 12.8 ± 0.3, and 21.8 ± 1.2 pC/N, respectively. A good agreement was found between the values of the piezoelectric moduli obtained in this work and the values obtained earlier by the quasi-static method.

Experimental Evidence of Long-Lived Electric Fields of Ionic Liquid Bilayers.

Herein we demonstrate that ionic liquids can form long-lived double layers, generating electric fields detectable by straightforward open circuit potential (OCP) measurements. In imidazolium-based ionic liquids an external negative voltage pulse leads to an exceedingly stable near-surface dipolar layer, whose field manifests as long-lived (∼1-100 h) discrete plateaus in OCP versus time traces. These plateaus occur within an ionic liquid-specific and sharp potential window, defining a simple experimental method to probe the onset of interfacial ordering phenomena, such as overscreening and crowding. Molecular dynamics modeling reveals that the OCP arises from the alignment of the individual ion dipoles to the external electric field pulse, with the magnitude of the resulting OCP correlating with the product of the projected dipole moment of the cation and the ratio between the cation diffusion coefficient and its volume. Our findings also reveal that a stable overscreened structure is more likely to form if the interface is first forced through crowding, possibly accounting for the scattered literature data on relaxation kinetics of near-surface structures in ionic liquids.

Electroluminescence in narrow-gap semiconductors CdxHg1-xTe under interband breakdown in an electric field

Within the framework of a simple two-band model, in the approximation of the method of effective parameters, the behavior of nonequilibrium carriers in solid solutions of the Cd x Hg 1-x Te (MCT) type in an external electric field is considered. The consideration is carried out for the range of values of the parameter x , in which the specified compound demonstrates the behavior of a narrow-gap semiconductor. Estimates show that for the real parameters of MCT samples in a wide range of variation of the value of x (and hence the width of the band gap) at an electric field exceeding some characteristic value of the interband breakdown field (depending on the parameter x and other physical parameters) in such systems, it is possible to obtain an inverse population distributions of carriers by energy. Moreover, the magnitude of the amplification factor at direct interband transitions can reach values up to 10 1 –10 2 cm −1 . The response of samples prepared from thick (not quantum-dimensional in terms of their thickness) MCT films to an external pulsed electric field is studied experimentally. The field was applied to the samples using ohmic contacts. The current-voltage characteristics of such samples and the dependences of the radiation intensity from the samples on the amplitude of the applied voltage pulses were obtained experimentally. The characteristic features of the responses obtained experimentally in these systems are discussed, as well as the possible prospects and difficulties for obtaining the laser effect using interband breakdown in an electric field. • Electroluminescence, narrow-gap semiconductors.

Calcium Delivery by Electroporation Induces In Vitro Cell Death through Mitochondrial Dysfunction without DNA Damages.

Adolescent cancer survivors present increased risks of developing secondary malignancies due to cancer therapy. Electrochemotherapy is a promising anti-cancer approach that potentiates the cytotoxic effect of drugs by application of external electric field pulses. Clinicians proposed to associate electroporation and calcium. The current study aims to unravel the toxic mechanisms of calcium electroporation, in particular if calcium presents a genotoxic profile and if its cytotoxicity comes from the ion itself or from osmotic stress. Human dermal fibroblasts and colorectal HCT-116 cell line were treated by electrochemotherapy using bleomycin, cisplatin, calcium, or magnesium. Genotoxicity, cytotoxicity, mitochondrial membrane potential, ATP content, and caspases activities were assessed in cells grown on monolayers and tumor growth was assayed in tumor spheroids. Results in monolayers show that unlike cisplatin and bleomycin, calcium electroporation induces cell death without genotoxicity induction. Its cytotoxicity correlates with a dramatic fall in mitochondrial membrane potential and ATP depletion. Opposite of magnesium, over seven days of calcium electroporation led to spheroid tumor growth regression. As non-genotoxic, calcium has a better safety profile than conventional anticancer drugs. Calcium is already authorized by different health authorities worldwide. Therefore, calcium electroporation should be a cancer treatment of choice due to the reduced potential of secondary malignancies.

Electron densities and temperatures of an atmospheric-pressure nanosecond pulsed helium plasma jet in air**{Electron properties in a nanosecond pulsed atmospheric plasma jet determined by laser Thomson scattering}.

We report temporally and spatially resolved electron property measurements of a 150 ns pulsed helium plasma jet in air operated at a low-repetition rate using Thomson laser scattering. A ring-shaped electron density distribution was revealed in the pulsed plasma jet at an axial distance of 1 mm from the electrode nozzle and started to converge after 5 mm. A peak electron density of 1 × 1020 m−3 was identified at the radius of the ring and close to the nozzle electrode. For a delay time ranging from 60 to 250 ns after the onset of the streamer, the electron temperature at the radius of the ring varied from 2.8 to 0.8 eV. Higher temperature >3.5 eV was also identified at regions with lower densities. Importantly, temporal development of the electron density and temperature of the plasma jet confirmed the strong dependence of guided streamer formation and propagation on the external pulsed electric field. The jet current measured during the rising and falling phases of the voltage pulse can be related to the peaks in the temporal development of the electron density.

Effect of electrochemotherapy with betulinic acid or cisplatin on regulation of heat shock proteins in metastatic human carcinoma cells invitro.

Betulinic acid (BTA) is naturally occurring triterpene that has received interest as a novel therapeutic substance with cytotoxicity towards a number of cancer cell lines. Despite the wide spectrum of biological and pharmacological effects, its effect may be limited its lipophobic properties. Therefore, strategies to improve the access of BTA to the cells are required to enhance the anticancer effects. Electroporation (EP) enables increased inflow of drugs into cancer cells, even at low doses, which may reduce the side effects caused by high doses of chemotherapy. The potential application of BTA in electrochemotherapy (ECT) in metastatic type of cancers was investigated in the present study. The efficacy of BTA with EP was estimated using a cell survival assay (MTT assay), microscopical morphology analysis and the immunocytochemical expression of heat shock proteins (HSPs). HSPs are molecules that protect the cell from harmful environmental, chemical and physical stresses, and ensure cell survival, recovery and proper functioning. HSP expression is induced various stress factors. Therefore, the expression of HSP27 and HSP70 was evaluated after cells were exposed to an external pulsed electric field and anticancer drugs. Facilitated drug delivery and the anticancer effect on metastatic tumor cells were evaluated in vitro. The effect of BTA was compared with cisplatin (CP), a standard cytostatic agent. Two different metastatic cancer cell lines were used, an ovary adenocarcinoma cell line (SW626) and melanoma cell line (Me45). BTA combined with EP exhibited similar efficacy to CP with EP after 24 and 48 h in SW626 and Me45 cancer cells. Me45 cells also had high HSP27 and low HSP70 immunosignals post‑ECT treatment. ECT caused increased expression of HSP27 and HSP70 proteins in SW626 cells, which were less sensitive to ECT than the Me45 melanoma cell line. The results indicate that BTA may be efficiently applied instead of CP in ECT approaches, but its activity differs between tumor cell lines.

Unidirectional quantum walk of two correlated particles: Manipulating bound-pair and unbound wave-packet components

We study the unidirectional transport of two-particle quantum wave-packets in a regular one-dimensional lattice. We show that the bound-pair state component behaves differently from unbound states when subjected to an external pulsed electric field. Thus, strongly entangled particles exhibit a quite distinct dynamics when compared to a single particle system. With respect to centroid motion, our numerical results are corroborated with an analytical expression obtained using a semi-classical approach. The wave function profile reveals that the particle–particle interaction induces the splitting of the initial wave-packet into two branches that propagate with specific directions and drift velocities. With a proper external field tuning, the wave-packet components can perform an unidirectional transport on the same or opposite directions. The amplitude of each mode is related to the degree of entanglement between particles, which presents a non monotonic dependence on the interaction strength.

Morphology and Electric Conductance Change Induced by Voltage Pulse Excitation in (GeTe)2/Sb2Te3 Superlattices.

Chalcogenide superlattice (SL) phase-change memory materials are leading candidates for non-volatile, energy-efficient electric memory where the electric conductance switching is caused by the atom repositioning in the constituent layers. Here, we study the time evolution of the electric conductance in [(GeTe)2/(Sb2Te3)1]4 SLs upon the application of an external pulsed electric field by analysing the structural and electrical responses of the SL films with scanning probe microscopy (SPM) and scanning probe lithography (SPL). At a low pulse voltage (1.6–2.3 V), a conductance switching delay of a few seconds was observed in some SL areas, where the switch to the high conductance state (HCS) is accompanied with an SL expansion under the strong electric field of the SPM probe. At a high pulse voltage (2.5–3.0 V), the HCS current was unstable and decayed in a few seconds; this is ascribed to the degradation of the HCS crystal phase under excessive heating. The reversible conductance change under a pulse voltage of opposite polarity emphasised the role of the electric field in the phase-transition mechanism.

Acquiring snapshots of the orientation of trans-membrane protein domains using a hybrid FRET pair

One challenge in studying the function of membrane-embedded proteins is determining the orientation of key domains in the context of the changing and dynamic membrane environment. We describe a confocal microscopy setup that utilizes external electric field pulses to direct dipicrylamine (DPA) to a membrane leaflet. The detection of FRET between DPA and a fluorescent probe attributes it to the inner or outer leaflet of a membrane. By utilizing short acquisition times and confocal imaging, this attribution could be made even in changing membrane environments. Our setup adds versatility to the study of the biological activity of membrane-embedded proteins.

English

The possibility of microbial reduction by external pulsed electric field (PEF) offers a new application for pulsed power technology. Applying PEF technology to food pasteurization is a promising non-thermal method. One of such application is prevention of microbial growth, an effect that is based on irrreversible permiabilization of cell membranes. The objective of this study was to increase the shelf life of tomato juice using PEF method. It is reported that the microbes present in tomato juice were inactivated by PEF process using co-axial and co-field continuous treatment chambers. The samples were subjected to different electric field intensities (30 and 50 kVcm-1) with the same flow rate (100 mL min-1) and the same pulse number (150 pulses). After treatment, in both co-axial and co-linear chambers, greater reduction in microbial counts were seen at higher intensity of 50 kVcm-1. The co-axial treatment chamber at 150 pulses was more effective than co-linear treatment chamber (1.16 and 0.77 log reduction). Key words: Pulsed electric field, co-field continuous flow treatment chamber, co-axial continuous flow treatment chamber, tomato juice, microbial growth reduction.

Stark-inducedL-mixing interferences in ultracold cesium Rydberg atoms

The $l$-mixing effect and state-transfer induced by an external electric field pulse in ultracold Rydberg gases are observed with cesium atoms excited to $\mathit{nS}$ states, and measured with a state selective field ionization technique. High-$l$ states are populated from the initially excited $\mathit{nS}$ states due to non-adiabatic transitions through avoided crossings that are formed between the $\mathit{nS}$ state and the ($n\ensuremath{-}4$) manifold. The population of the product state is investigated as a function of the electric field pulse parameters. The coherent property of the transfer is demonstrated using a 2-pulse sequence and the results are consistent with the theoretical calculations. This $l$-mixing phenomenon in the electric field may be used to help forming a molecular potential and create Rydberg molecules.

State transfer of ultracold nS Rydberg atoms

The state transfer of nS Rydberg atoms induced by external pulsed electric field has been investigated. Cold nS Rydberg atoms are prepared by the two-photon transition and the selective field-ionization method is used to detect the Rydberg atoms and "P" state due to the state mixing. The avoided crossing of nS and (n-4) manifold is studied and the dependence of the state transfer rate on the strength of pulsed field is obtained. Experimental result is interpreted by using Stark effect of electric field and it shows consistency between experiment and calculation.

Application of electric field ionization method to detect the high-lying Rydberg states of Eu I

The 4f7 6s(9S)np 8PJ (J=5/2, 7/2, 9/2) Rydberg series converging to the first ionization limit 4f7 6s 9S4 of the Eu atom using the three-step laser excitation and electric-field-ionization (EFI) method are studied. First, the Eu atom is excited from the 4f7 6s2 8So7/2 ground state to the 4f76s7s 8So7/2 state through the 4f7 6s6p 10P9/2 state by the first two dye lasers. Next, it is populated to many higher-n members of the 4f7 6s(9S)np 8PJ Rydberg series by the third dye laser whose wavelength is scanned within a certain range. Finally, the atom in these higher-n states is ionized by the external pulsed electric field. With the field strength up to 2 kV/cm, we can detect the atom in 4f76s(9S)np 8PJ states with n>40. With the given laser line width, the level energies of Rydberg states with n as high as 72 can be determined. We not only confirm the previous data on the 4f76s(9S) np 8PJ Rydberg series, but also extend the n-value assignment significantly by detecting more states.

Chaotic ionization of a Rydberg atom subjected to alternating kicks: Role of phase-space turnstiles

We study the ionization of a highly excited Rydberg atom subjected to a periodic sequence of external electric-field pulses. Such systems are important laboratory and theoretical models of classical and quantum chaos. Furthermore, a good theoretical understanding of this chaos is important for controlling electronic states in atoms, as has been demonstrated in a series of recent experiments on the creation and control of electronic wave packets. Here, we present a theoretical analysis of the chaotic ionization of a hydrogen atom subjected to alternating positive and negative impulses. This analysis is based on the observation that the ionization of the atom is due to a turnstile in phase space which promotes the electronic state from negative to positive energy. The geometry of the lobes associated with the turnstile provides a clear picture of how the ionization process proceeds. Using this geometric intuition, we propose two experimental protocols to directly reveal the importance of the turnstile lobes in the laboratory.