Electrical Conductivity Measurement in Human Liver Tissue: Assessment on Normal vs. Tumor Tissue and under In Vivo vs. Ex Vivo Conditions.

Background: This study evaluated electrical conductivity in human liver tissue in the 3-1000 kHz frequency range to compare normal versus tumor tissues under in vivo versus ex vivo conditions.

Methods: Previous informed consent was obtained from twenty patients undergoing liver resection in whom liver electrical conductivity was measured during surgery and after resection.

Result: We found higher electrical conductivity values in tumor tissues than in normal tissue in both in vivo (0.

In Vitro Imaging and Molecular Characterization of Ca Flux Modulation by Nanosecond Pulsed Electric Fields.

In recent years, the application of pulsed electric fields with very short durations (nanoseconds) and extremely high amplitudes (MV/m) has been investigated for novel medical purposes. Various electric protocols have been explored for different objectives, including the utilization of fractionated pulse doses to enhance cell electrosensitization to the uptake of different markers or an increase in apoptosis. This study focused on the use of fluorescence imaging to examine molecular calcium fluxes induced by different fractionated protocols of short electric pulses in neuroblastoma (SH-SY5Y) and mesenchymal stem cells (HaMSCs) that were electroporated using nanosecond pulsed electric fields.

Dynamics of High-Density Unipolar Epicardial Electrograms During PFA.

Background: Pulsed field ablation (PFA) is a novel nonthermal cardiac ablation technology based on irreversible electroporation (IRE). While areas of IRE lead to durable lesions, the surrounding regions, where reversible electroporation occurs, recover. The behavior of local electrograms in areas of different electroporation levels remains unknown.

Parametric Study of Pulsed Field Ablation With Biphasic Waveforms in an In Vivo Heart Model: The Role of Frequency.

Background: Pulsed field ablation (PFA) is a novel nonthermal cardiac ablation technology based on irreversible electroporation. Unfortunately, the characteristics of the electric field waveforms used in clinical and experimental PFA are not typically reported. This study examines the effect of the frequency of biphasic waveforms and compares biphasic to monophasic waveforms.

A computational comparison of radiofrequency and pulsed field ablation in terms of lesion morphology in the cardiac chamber.

Pulsed Field Ablation (PFA) has been developed over the last years as a novel electrical ablation technique for treating cardiac arrhythmias. It is based on irreversible electroporation which is a non-thermal phenomenon innocuous to the extracellular matrix and, because of that, PFA is considered to be safer than the reference technique, Radiofrequency Ablation (RFA). However, possible differences in lesion morphology between both techniques have been poorly studied.

Biological effects of ultrashort electric pulses in a neuroblastoma cell line: the energy density role.

Background: Despite the numerous literature results about biological effects of electromagnetic field (EMF) exposure, the interaction mechanisms of these fields with organisms are still a matter of debate. Extremely low frequency (ELF) MFs can modulate redox homeostasis and we showed that 24 h exposure to 50 Hz-1 mT has a pro-oxidant effect and effects on the epigenome of SH-SY5Y cells, decreasing miR-34b/c expression through the hypermethylation of their promoter.

Methods: Here, we investigated the role of the electromagnetic deposited energy density (ED) during exposures lasting 24 h to 1 mT amplitude MFs at a frequency of 50 Hz in inducing the above mentioned effects.

Modeling Methods for Treatment Planning in Overlapping Electroporation Treatments.

Objective: Irreversible electroporation (IRE) is a non-thermal tissue ablation therapy which is induced by applying high voltage waveforms across electrode pairs. When multiple electrode pairs are sequentially used, the treatment volume (TV) is typically computed as the geometric union of the TVs of individual pairs. However, this method neglects that some regions are exposed to overlapping treatments.

Comparing High-Frequency With Monophasic Electroporation Protocols in an In Vivo Beating Heart Model.

This study compared monophasic 100-μs pulses with high-frequency electroporation (HF-EP) bursts using an in vivo animal model. Myocardial damage was evaluated by histologic analysis. Compared with 10 monophasic pulses, 20 bursts of HF-EP at 100 and 150 kHz were associated with less damage.

Electrophoresis-assisted accumulation of conductive nanoparticles for the enhancement of cell electropermeabilization.

The use of conductive nanoparticles (NPs) was previously proposed as a way to locally amplify the electric field (EF) intensity at the cell membrane to enhance cell electroporation. To achieve this, a close distance between the NPs and the cell membrane is mandatory. Here, a new method to improve the contact between NPs and cell surface using the effects of electric pulses (electrophoretic forces) is explored.

Physiological changes may dominate the electrical properties of liver during reversible electroporation: Measurements and modelling.

This study presents electrical measurements (both conductivity during the pulses and impedance spectroscopy before and after) performed in liver tissue of mice during electroporation with classical electrochemotherapy conditions (8 pulses of 100 µs duration). A four-needle electrode arrangement inserted in the tissue was used for the measurements. The undesirable effects of the four-electrode geometry, notably concerning its sensitivity, were quantified and discussed showing how the electrode geometry chosen for the measurements can impact the results.

Monitoring the molecular composition of live cells exposed to electric pulses via label-free optical methods.

The permeabilization of the live cells membrane by the delivery of electric pulses has fundamental interest in medicine, in particular in tumors treatment by electrochemotherapy. Since underlying mechanisms are still not fully understood, we studied the impact of electric pulses on the biochemical composition of live cells thanks to label-free optical methods: confocal Raman microspectroscopy and terahertz microscopy. A dose effect was observed after cells exposure to different field intensities and a major impact on cell peptide/protein content was found.

Possible molecular and cellular mechanisms at the basis of atmospheric electromagnetic field bioeffects.

Mechanisms of how electromagnetic (EM) field acts on biological systems are governed by the same physics regardless of the origin of the EM field (technological, atmospheric...

Conductive nanoparticles improve cell electropermeabilization.

Conducive nanoparticles (NPs) were proposed to locally amplify the external electric field (EF) intensity at the cell surface to improve cell electroporation. To better understand the physical mechanisms behind this improvement, different types of NPs and several incubation conditions were applied to adherent cells in the present study. The enhancement of electroporation was observed in the presence of conductive NPs but not when non-conductive NPs were used.

Successful Tumor Electrochemotherapy Using Sine Waves.

Objective: The purpose of this work is to assess the ability of sine waves to perform electrochemotherapy (ECT) and to study the dependence of the frequency of the applied sine wave on the treatment efficacy.

Methods: A subcutaneous tumor model in mice was used, and the electric field was delivered in combination with bleomycin. Sinusoidal electric fields of different frequencies, amplitudes, and durations were compared to square waves.

Impact of the number of electric pulses on cell electrochemotherapy in vitro: Limits of linearity and saturation.

In this study the evolution in the efficiency of electrochemotherapy (reversible electroporation) with pulse number was assessed in vitro. Experiments were performed using 100 μs pulses at different electric field intensities and the chemotherapeutic agent bleomycin. Additionally, electrical impedance spectroscopy measurements were used as a different method to study in real time the changes produced on cells with pulse number during trains of consecutive pulses.

In vitro analysis of various cell lines responses to electroporative electric pulses by means of electrical impedance spectroscopy.

This paper reports the comparative analysis, by means of electric impedance spectroscopy measurements, of three different cell lines subjected to electroporative pulses. The multifrequency information is recorded simultaneously at 21 frequency values in the range between 5 kHz and 1.3 MHz using a multisine based measuring approach.

Sine wave electropermeabilization reveals the frequency-dependent response of the biological membranes.

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.

Pyroelectricity as a possible mechanism for cell membrane permeabilization.

The effects of pyroelectricity on cell membrane permeability had never been explored. Pyroelectricity consists in the generation of an electric field in the surface of some materials when a change in temperature is produced. In the present study, tourmaline microparticles, which are known to display pyroelectrical properties, were subjected to different changes in temperature upon exposure to cells in order to induce an electric field at their surface.

Recognition of Fibrotic Infarct Density by the Pattern of Local Systolic-Diastolic Myocardial Electrical Impedance.

Myocardial electrical impedance is a biophysical property of the heart that is influenced by the intrinsic structural characteristics of the tissue. Therefore, the structural derangements elicited in a chronic myocardial infarction should cause specific changes in the local systolic-diastolic myocardial impedance, but this is not known. This study aimed to characterize the local changes of systolic-diastolic myocardial impedance in a healed myocardial infarction model.

Myocardial contractility assessed by dynamic electrical impedance measurements during dobutamine stress.

In this study, the electrical impedance of myocardial tissue is measured dynamically during the cardial cycle. The multisine-based approach used to perform electrical impedance spectroscopy (EIS) measurements allows acquiring complete spectral impedance information of the tissue dynamics during contraction. Measurements are performed in situ in the left ventricule of swines during contractility stress tests induced by dobutamine infusion.

Early detection of acute transmural myocardial ischemia by the phasic systolic-diastolic changes of local tissue electrical impedance.

Myocardial electrical impedance is influenced by the mechanical activity of the heart. Therefore, the ischemia-induced mechanical dysfunction may cause specific changes in the systolic-diastolic pattern of myocardial impedance, but this is not known. This study aimed to analyze the phasic changes of myocardial resistivity in normal and ischemic conditions.

Interpulse multifrequency electrical impedance measurements during electroporation of adherent differentiated myotubes.

In this study, electrical impedance spectroscopy measurements are performed during electroporation of monolayers of differentiated myotubes. The time resolution of the system (1 spectrum/ms) enable 860 full spectra (21 frequencies from 5 kHz to 1.3 MHz) to be acquired during the time gap between consecutive pulses (interpulse) of a classical electroporation treatment (8 pulses, 100 μs, 1 Hz).

A new spiral microelectrode assembly for electroporation and impedance measurements of adherent cell monolayers.

In this study, a new microelectrode assembly based on spiral geometry applicable to in situ electroporation of adherent cell monolayers on standard multiwell plates is presented. Furthermore, the structure is specially conceived to perform electrical impedance spectroscopy (EIS) measurements during electroporation. Its performance for cell membrane permeabilization is tested with a fluorescent probe.

Automatic system for electroporation of adherent cells growing in standard multi-well plates.

In this study an automatic system is presented to perform electroporation, also known as electropermeabilization, on adherent cells. It is an intention of this system to apply electric field pulses directly to cells growing in standard multi-well plates as a step forward to include this technique in standard laboratory protocols. An interdigitated microelectrode assembly constructed with Printed Circuit Board (PCB) is placed closely above the cell monolayer, and in order to avoid direct contact with cells, small micro-separators were included in the structure.

Design and implementation of a microelectrode assembly for use on noncontact in situ electroporation of adherent cells.

In situ electroporation of adherent cells provides significant advantages with respect to electroporation systems for suspension cells, such as causing minimal stress to cultured cells and simplifying and saving several steps within the process. In this study, a new electrode assembly design is shown and applied to in situ electroporate adherent cell lines growing in standard multiwell plates. We designed an interdigitated array of electrodes patterned on copper with printed circuit board technology and covered with nickel/gold.