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

Unexpected transient atrioventricular block and slow junctional rhythm using pulsed field ablation for slow pathway modification: Excited or cautious for ablators

BACKGROUND

Data regarding the effects of pulsed field ablation (PFA) on atrioventricular nodal reentrant tachycardia (AVNRT) are limited.

OBJECTIVE

This study was undertaken to evaluate the outcomes of PFA for AVNRT and its impact on dual-pathway electrophysiology.

METHODS

A larger cohort of patients with typical AVNRT underwent slow pathway (SP) modification (SPM) using a focal PFA catheter in a biphasic/bipolar manner. The primary endpoints were the efficacy and safety of PFA during the procedure and at 6-month follow-up.

RESULTS

The acute success of SPM was achieved in all 40 patients. The total ablation time was 7.9 ± 3.8 seconds for 6.4 ± 2.2 ablation sites (ASs). Slow junctional rhythm (SJR) was induced in 32 (80%) patients, lasting 28.9 ± 10.3 seconds in 3.0 ± 1.1 ASs per patient. SP was located 11.1 ± 1.2 mm from the largest His activation (LHA). At 9 ASs, SJR could be reinduced after an increase of contact force (CF) from 1.3 ± 0.5g to 6.4 ± 1.3 g (P < .0001). Transient atrioventricular block (AVB) was recorded in 7 (17.5%) patients (1 second-degree and 6 third-degree AVB) lasting 435.3 ± 227.4 seconds, with a shorter AS-LHA distance than patients without AVB (7.7 ± 0.6 mm vs. 11.3 ± 1 mm; P < .0001). PFA-related delayed atrial-His (n = 6) and His-atrial (n = 1) conduction preceded transient AVB with a constant His-ventricular interval. Normal PR interval was restored within 24 hours. All patients maintained sinus rhythm without any significant adverse events during 6-month follow-up.

CONCLUSION

Despite the high efficiency of PFA for SPM, the notable incidence of transient AVB warranted caution when applying it near the His bundle. SJR frequently occurred during SPM and was dependent on moderate CF.

Enhancing protein extraction from heterotrophic Auxenochlorella protothecoides microalgae through emerging cell disruption technologies combined with incubation

This study evaluated pulsed electric fields (PEF) and ultrasonication (US) combined with incubation to enhance cell disruption and protein extraction from Auxenochlorella protothecoides, comparing them to conventional high-pressure homogenization (HPH). A 5 h incubation enhanced protein yield by 79.4 % for PEF- and 27.2 % for US-treated samples. Extending the incubation to 24 h resulted in a total yield increase of 122 % for PEF (0.25 ± 0.03 kgEP kgTP-1) and 51.9 % for US (0.20 ± 0.02 kgEP-1 kgTP-1). Autofermentation in untreated cells after 24 h resulted in protein release with lower yields than all other treated and incubated samples. While HPH had the highest protein yield (0.58 ± 0.04 kgEP kgTP-1), PEF-incubation after 5 h (56.6 ± 5.3 MJ kgEP-1) and 24 h (49.5 ± 3.7 MJ kgEP-1) were 1.5 and 1.7-times more energy-efficient than HPH (82.9 ± 7.8 MJ kgEP-1). PEF combined incubation is an energy-efficient and targeted protein extraction method in heterotrophic A. protothecoides biorefinery.

Outcomes of Focal Pulsed Field Ablation for Paroxysmal Supraventricular Tachycardia

BACKGROUND

Pulsed field ablation (PFA) is primarily used for treatment of atrial fibrillation as it provides better safety and efficacy. However, there are limited data available on the use of PFA for paroxysmal supraventricular tachycardia (PSVT). The study sought to describe the outcomes of PSVT ablation with a novel focal contact force (CF)-sensing PFA.

METHODS

In this first-in-human pilot study, a focal CF-sensing PFA catheter was used for mapping and ablation navigated with an electroanatomic mapping system (EAMS). Pulsed field energy was delivered as biphasic/bipolar electrical pulse trains with 2000 V/delivery. CF was controlled from 2 g to 10 g during PFA.

RESULTS

Procedural acute success was achieved without general anaesthesia or conscious sedation in all 10 patients, including 7 patients diagnosed with typical atrioventricular nodal re-entrant tachycardias and 3 patients with orthodromic reciprocating tachycardias. Successful target ablation time was 2.0 ± 0.5 seconds per patient, and the acute procedural success at the first single site was achieved in 5 patients. The mean skin-to-skin procedure time was 79.4 ± 15 minutes, PFA catheter dwell time was 50.1 ± 14 minutes, and fluoroscopy time was 6.2 ± 7 minutes. Maintenance of sinus rhythm was observed in all patients within 6-month follow-up. No serious adverse events occurred in any subjects during PFA or during the 6-month follow-up.

CONCLUSIONS

A focal CF-sensing PFA catheter could effectively, rapidly, and safely ablate PSVT in conscious patients.

CLINICAL TRIAL REGISTRATION

NCT05770921.

Enhanced Cellular Doxorubicin Uptake via Delayed Exposure Following Nanosecond Pulsed Electric Field Treatment: An In Vitro Study

The combination of nanosecond Pulsed Electric Field (nsPEF) with pharmaceuticals is a pioneering therapeutic method capable of enhancing drug uptake efficacy in cells. Utilizing nsPEFs configured at 400 pulses, an electric field strength of 15 kV/cm, a pulse duration of 100 ns, and a repetition rate of 10 pulses per second (PPS), we combined the nsPEF with a low dose of doxorubicin (DOX) at 0.5 μM. Upon verifying that cells could continuously internalize DOX from the surrounding medium within 1 h post nsPEF exposure, we set the DOX exposure period to 10 min and contrasted the outcomes of varying sequences of DOX and nsPEF administration: pulsing followed by DOX, DOX followed by pulsing, and DOX applied 40 min after pulsing. Flow cytometry, CCK-8 assays, and transmission electron microscopy (TEM) were employed to examine intracellular DOX accumulation, cell viability, apoptosis, cell cycle, and ultrastructural transformations. Our findings demonstrate that exposing cells to DOX 40 min subsequent to nsPEF treatment can effectively elevate intracellular DOX levels, decrease cell viability, and inhibit the cell cycle. This research work presents a novel approach to enhance DOX uptake efficiency with moderate conditions of both DOX and nsPEF.

Catheter-Based Electroporation: A Novel Technique for Catheter Ablation of Cardiac Arrhythmias

Catheter ablation of arrhythmias is now standard of care in invasive electrophysiology. Current ablation strategies are based on the use of thermal energy. With continuous efforts to optimize thermal energy delivery, effectiveness has greatly improved; however, safety concerns persist. This review focuses on a novel ablation technology, irreversible electroporation (IRE), also known as pulsed-field ablation which may be a safer alternative for arrhythmia management. Pulsed-field ablation is thought to be a nonthermal ablation that applies short-duration high-voltage electrical fields to ablate myocardial tissue with high selectivity and durability while sparing important neighboring structures such as the esophagus and phrenic nerves. There are multiple ongoing studies investigating the potential superior outcomes of IRE compared to radiofrequency ablation in treating patients with atrial and ventricular arrhythmias. In this review, we describe the current evidence of preclinical and clinical trials that have shown promising results of catheter-based IRE.

Electrochemotherapy in radiotherapy-resistant epidural spinal cord compression in metastatic cancer patients

OBJECTIVE

To report efficacy and safety of percutaneous electrochemotherapy (ECT) in patients with radiotherapy-resistant metastatic epidural spinal cord compression (MESCC).

MATERIAL/ METHODS

This retrospective study analyzed all consecutive patients treated with bleomycin-based ECT between February-2020 and September-2022 in a single tertiary referral cancer center. Changes in pain were evaluated with the Numerical Rating Score (NRS), in neurological deficit with the Neurological Deficit Scale, and changes in epidural spinal cord compression were evaluated with the epidural spinal cord compression scale (ESCCS) using an MRI.

RESULTS

Forty consecutive solid tumour patients with previously radiated MESCC and no effective systemic treatment options were eligible. With a median follow-up of 5.1 months [1-19.1], toxicities were temporary acute radicular pain (25%), prolonged radicular hypoesthesia (10%), and paraplegia (7.5%). At 1 month, pain was significantly improved over baseline (median NRS: 1.0 [0-8] versus 7.0 [1.0-10], P < .001) and neurological benefits were considered as marked (28%), moderate (28%), stable (38%), or worse (8%). Three-month follow-up (21 patients) confirmed improved over baseline (median NRS: 2.0 [0-8] versus 6.0 [1.0-10], P < .001) and neurological benefits were considered as marked (38%), moderate (19%), stable (33.5%), and worse (9.5%). One-month post-treatment MRI (35 patients) demonstrated complete response in 46% of patients by ESCCS, partial response in 31%, stable disease in 23%, and no patients with progressive disease. Three-month post-treatment MRI (21 patients) demonstrated complete response in 28.5%, partial response in 38%, stable disease in 24%, and progressive disease in 9.5%.

CONCLUSIONS

This study provides the first evidence that ECT can rescue radiotherapy-resistant MESCC.

Optimization of Transpedicular Electrode Insertion for Electroporation-Based Treatments of Vertebral Tumors

Electroporation-based treatments such as electrochemotherapy and irreversible electroporation ablation have sparked interest with respect to their use in medicine. Treatment planning involves determining the best possible electrode positions and voltage amplitudes to ensure treatment of the entire clinical target volume (CTV). This process is mainly performed manually or with computationally intensive genetic algorithms. In this study, an algorithm was developed to optimize electrode positions for the electrochemotherapy of vertebral tumors without using computationally intensive methods. The algorithm considers the electric field distribution in the CTV, identifies undertreated areas, and uses this information to iteratively shift the electrodes from their initial positions to cover the entire CTV. The algorithm performs successfully for different spinal segments, tumor sizes, and positions within the vertebra. The average optimization time was 71 s with an average of 4.9 iterations performed. The algorithm significantly reduces the time and expertise required to create a treatment plan for vertebral tumors. This study serves as a proof of concept that electrode positions can be determined (semi-)automatically based on the spatial information of the electric field distribution in the target tissue. The algorithm is currently designed for the electrochemotherapy of vertebral tumors via a transpedicular approach but could be adapted for other anatomic sites in the future.

Cardiac ablation with pulsed electric fields: principles and biophysics

Pulsed electric fields (PEFs) have emerged as an ideal cardiac ablation modality. At present numerous clinical trials in humans are exploring PEF as an ablation strategy for both atrial and ventricular arrhythmias, with early data showing significant promise. As this is a relatively new technology there is limited understanding of its principles and biophysics. Importantly, PEF biophysics and principles are starkly different to current energy modalities (radiofrequency and cryoballoon). Given the relatively novel nature of PEFs, this review aims to provide an understanding of the principles and biophysics of PEF ablation. The goal is to enhance academic research and ultimately enable optimization of ablation parameters to maximize procedure success and minimize risk.

Reduction of muscle contraction and pain in electroporation-based treatments: An overview

BACKGROUND

In the first studies of electrochemotherapy (ECT), small cutaneous metastases were treated and only mild or moderate pain was observed; therefore, pain was not considered a significant issue. As the procedure began to be applied to larger cutaneous metastases, pain was reported more frequently. For that reason, reduction of both muscle contractions and pain have been investigated over the years.

AIM

To present an overview of different protocols described in literature that aim to reduce muscle contractions and pain caused by the electroporation (EP) effect in both ECT and irreversible EP treatments.

METHODS

Thirty-three studies published between January 1999 and November 2020 were included. Different protocol designs and electrode geometries that reduce patient pain and the number of muscle contractions and their intensity were analysed.

RESULTS

The analysis showed that both high frequency and bipolar/biphasic pulses can be used to reduce pain and muscle contractions in patients who undergo EP treatments. Moreover, adequate electrode design can decrease EP-related morbidity. Particularly, needle length, diameter and configuration of the distance between the needles can be optimised so that the muscle volume crossed by the current is reduced as much as possible. Bipolar/biphasic pulses with an inadequate pulse length seem to have a less evident effect on the membrane permeability compared with the standard pulse protocol. For that reason, the number of pulses and the voltage amplitude, as well as the pulse duration and frequency, must be chosen so that the dose of delivered energy guarantees EP efficacy.

CONCLUSION

Pain reduction in EP-based treatments can be achieved by appropriately defining the protocol parameters and electrode design. Most results can be achieved with high frequency and/or bipolar/biphasic pulses. However, the efficacy of these alternative protocols remains a crucial point to be assessed further.

A thermodynamic scaling law for electrically perturbed lipid membranes: Validation with steepest entropy ascent framework

Experimental evidence has demonstrated the ability of transient pulses of electric fields to alter mammalian cell behavior. Strategies with these pulsed electric fields (PEFs) have been developed for clinical applications in cancer therapeutics, in-vivo decellularization, and tissue regeneration. Successful implementation of these strategies involve understanding how PEFs impact the cellular structures and, hence, cell behavior. The caveat, however, is that the PEF parameter space (i.e., comprising different pulse widths, amplitudes, number of pulses) is large, and design of experiments to explore all possible combinations of pulse parameters is prohibitive from a cost and time standpoint. In this study, a scaling law based on the Ising model is introduced to understand the impact of PEFs on the outer cell lipid membrane so that an understanding developed in one PEF pulse regime may be extended to another. Combining non-Markovian Monte Carlo techniques to determine density-of-states with a novel non-equilibrium thermodynamic framework based on the principle of steepest entropy ascent, the applicability of this scaling model to predict the behavior of both thermally quenched and electrically perturbed lipid membranes is demonstrated. A comparison of the predictions made by the steepest-entropy-ascent quantum thermodynamic (SEAQT) framework to experimental data is performed to validate the robustness of this computational methodology and the resulting scaling law.

10 ns PEFs induce a histological response linked to cell death and cytotoxic T-lymphocytes in an immunocompetent mouse model of peritoneal metastasis

PURPOSE

The application of nanosecond pulsed electric fields (nsPEFs) could be an effective therapeutic strategy for peritoneal metastasis (PM) from colorectal cancer (CRC). The aim of this study was to evaluate in vitro the sensitivity of CT-26 CRC cells to nsPEFs in combination with chemotherapeutic agents, and to observe the subsequent in vivo histologic response.

METHODS

In vitro cellular assays were performed to assess the effects of exposure to 1, 10, 100, 500 and 1000 10 ns pulses in a cuvette or bi-electrode system at 10 and 200 Hz. nsPEF treatment was applied alone or in combination with oxaliplatin and mitomycin. Cell death was detected by flow cytometry, and permeabilization and intracellular calcium levels by fluorescent confocal microscopy after treatment. A mouse model of PM was used to investigate the effects of in vivo exposure to pulses delivered using a bi-electrode system; morphological changes in mitochondria were assessed by electron microscopy. Fibrosis was measured by multiphoton microscopy, while the histological response (HR; hematoxylin-eosin-safran stain), proliferation (KI67, DAPI), and expression of immunological factors (CD3, CD4, CD8) were evaluated by classic histology.

RESULTS

10 ns PEFs exerted a dose-dependent effect on CT-26 cells in vitro and in vivo, by inducing cell death and altering mitochondrial morphology after plasma membrane permeabilization. In vivo results indicated a specific CD8+ T cell immune response, together with a strong HR according to the Peritoneal Regression Grading Score (PRGS).

CONCLUSIONS

The effects of nsPEFs on CT-26 were confirmed in a mouse model of CRC with PM.

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...), given that EM parameters are the same. We draw from a large body of literature of bioeffects of a man-made electromagnetic field. In this paper, we performed a focused review on selected possible mechanisms of how atmospheric electromagnetic phenomena can act at the molecular and cellular level. We first briefly review the range of frequencies and field strengths for both electric and magnetic fields in the atmosphere. Then, we focused on a concise description of the current knowledge on weak electric and magnetic field bioeffects with possible molecular mechanisms at the basis of possible EM field bioeffects combined with modeling strategies to estimate reliable outcomes and speculate about the biological effects linked to lightning or pyroelectricity. Indeed, we bring pyroelectricity as a natural source of voltage gradients previously unexplored. While very different from lightning, it can result in similar bioeffects based on similar mechanisms, which can lead to close speculations on the importance of these atmospheric electric fields in the evolution.

Bioluminescence as a sensitive electroporation indicator in sub-microsecond and microsecond range of electrical pulses

The cell membrane permeabilization in electroporation studies is usually quantified using fluorescent markers such as propidium iodide (PI) or YO-PRO, while Chinese Hamster Ovary cell line frequently serves as a model. In this work, as an alternative, we propose a sensitive methodology for detection and analysis of electroporation phenomenon based on bioluminescence. Luminescent mice myeloma SP2/0 cells (transfected using Luciferase-pcDNA3 plasmid) were used as a cell model. Electroporation has been studied using the 0.1-5 μs × 250 and 100 μs × 1-8 pulsing protocols in 1-2.5 kV/cm PEF range. It was shown that the bioluminescence response is dependent on the cell permeabilization state and can be effectively used to detect even weak permeabilization. During saturated permeabilization the methodology accurately predicts the losses of cell viability due to irreversible electroporation. The results have been superpositioned with permeabilization and pore resealing (1 h post-treatment) data using PI. Also, the viability of the cells was evaluated. Lastly, the SP2/0 tumors have been developed in BALB/C mice and the methodology has been tested in vivo using electrochemotherapy with bleomycin.

Electrochemotherapy Using Doxorubicin and Nanosecond Electric Field Pulses: A Pilot in Vivo Study

Pulsed electric field (PEF) is frequently used for intertumoral drug delivery resulting in a well-known anticancer treatment-electrochemotherapy. However, electrochemotherapy is associated with microsecond range of electrical pulses, while nanosecond range electrochemotherapy is almost non-existent. In this work, we analyzed the feasibility of nanosecond range pulse bursts for successful doxorubicin-based electrochemotherapy in vivo. The conventional microsecond (1.4 kV/cm × 100 µs × 8) procedure was compared to the nanosecond (3.5 kV/cm × 800 ns × 250) non-thermal PEF-based treatment. As a model, Sp2/0 tumors were developed. Additionally, basic current and voltage measurements were performed to detect the characteristic conductivity-dependent patterns and to serve as an indicator of successful tumor permeabilization both in the nano and microsecond pulse range. It was shown that nano-electrochemotherapy can be the logical evolution of the currently established European Standard Operating Procedures for Electrochemotherapy (ESOPE) protocols, offering better energy control and equivalent treatment efficacy.

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. Numerical modelling was applied to the information collected during the pulse, and to the impedance spectra acquired before and after the pulses sequence. Our results show that the numerical results were not consistent, suggesting that other collateral phenomena not considered in the model are at work during electroporation in vivo. We show how the modification in the volume of the intra and extra cellular media, likely caused by the vascular lock effect, could at least partially explain the recorded impedance evolution. In the present study we demonstrate the significant impact that physiological effects have on impedance changes following electroporation at the tissue scale and the potential need of introducing them into the numerical models. The code for the numerical model is publicly available at https://gitlab.inria.fr/poignard/4-electrode-system.

Real-Time Impedance Monitoring During Electroporation Processes in Vegetal Tissue Using a High-Performance Generator

Classical application of electroporation is carried out by using fixed protocols that do not clearly assure the complete ablation of the desired tissue. Nowadays, new methods that pursue the control of the treatment by studying the change in impedance during the applied pulses as a function of the electric field are being developed. These types of control seek to carry out the treatment in the fastest way, decreasing undesired effects and treatment time while ensuring the proper tumour ablation. The objective of this research is to determine the state of the treatment by continuously monitoring the impedance by using a novel versatile high-voltage generator and sensor system. To study the impedance dynamics in real time, the use of pulses of reduced voltage, below the threshold of reversible electroporation, is tested to characterise the state-of-the-treatment without interfering with it. With this purpose, a generator that provides both low voltage for sense tissue changes and high voltage for irreversible electroporation (IRE) was developed. In conclusion, the characterisation of the effects of electroporation in vegetal tissue, combined with the real-time monitoring of the state-of-the-treatment, will enable the provision of safer and more effective treatments.