Oxidative Effects during Irreversible Electroporation of Melanoma Cells-In Vitro Study

Mitochondrial depolarization and ATP loss during high frequency nanosecond and microsecond electroporation

It is predicted that ultra-short electric field pulses (nanosecond) can selectively permeabilize intracellular structures (e.g., mitochondria) without significant effects on the outer cell plasma membrane. Such a phenomenon would have high applicability in cancer treatment and could be employed to modulate cell death type or immunogenic response. Therefore, in this study, we compare the effects of 100 µs x 8 pulses (ESOPE - European Standard Operating Procedures on Electrochemotherapy) and bursts of 100 ns pulses for modulation of the mitochondria membrane potential. We characterize the efficacies of various protocols to trigger permeabilization, depolarize mitochondria (evaluated 1 h  after treatment), the extent of ATP depletion and generation of reactive oxygen species (ROS). Finally, we employ the most prominent protocols in the context of Ca2+ electrochemotherapy in vitro. We provide experimental proof that 7.5-12.5 kV/cm x 100 ns pulses can be used to modulate mitochondrial potential, however, the permeabilization of the outer membrane is still a prerequisite for depolarization. Similar to 100 µs x 8 pulses, the higher the permeabilization rate, the higher the mitochondrial depolarization. Nevertheless, 100 ns pulses result in lesser ROS generation when compared to ESOPE, even when the energy input is several-fold higher than for the microsecond procedure. At the same time, it shows that even the short 100 ns pulses can be successfully used for Ca2+ electrochemotherapy, ensuring excellent cytotoxic efficacy.

Pulsed electric field induces exocytosis and overexpression of MAGE antigens in melanoma

Nanosecond pulsed electric field (nsPEF) has emerged as a promising approach for inducing cell death in melanoma, either as a standalone treatment or in combination with chemotherapeutics. However, to date, there has been a shortage of studies exploring the impact of nsPEF on the expression of cancer-specific molecules. In this investigation, we sought to assess the effects of nsPEF on melanoma-specific MAGE (Melanoma Antigen Gene Protein Family) expression. To achieve this, melanoma cells were exposed to nsPEF with parameters set at 8 kV/cm, 200 ns duration, 100 pulses, and a frequency of 10 kHz. We also aimed to comprehensively describe the consequences of this electric field on melanoma cells' invasion and proliferation potential. Our findings reveal that following exposure to nsPEF, melanoma cells release microvesicles containing MAGE antigens, leading to a simultaneous increase in the expression and mRNA content of membrane-associated antigens such as MAGE-A1. Notably, we observed an unexpected increase in the expression of PD-1 as well. While we did not observe significant differences in the cells' proliferation or invasion potential, a remarkable alteration in the cells' metabolomic and lipidomic profiles towards a less aggressive phenotype was evident. Furthermore, we validated these results using ex vivo tissue cultures and 3D melanoma culture models. Our study demonstrates that nsPEF can elevate the expression of membrane-associated proteins, including melanoma-specific antigens. The mechanism underlying the overexpression of MAGE antigens involves the initial release of microvesicles containing MAGE antigens, followed by a gradual increase in mRNA levels, ultimately resulting in elevated expression of MAGE antigens post-experiment. These findings shed light on a novel method for modulating cancer cells to overexpress cancer-specific molecules, thereby potentially enhancing their sensitivity to targeted anticancer therapy.

Effects of bipolar irreversible electroporation with different pulse durations in a prostate cancer mouse model

Irreversible electroporation (IRE) is a non-thermal ablation technique for local tumor treatment known to be influenced by pulse duration and voltage settings, affecting its efficacy. This study aims to investigate the effects of bipolar IRE with different pulse durations in a prostate cancer mouse model. The therapeutic effectiveness was assessed with in vitro cell experiments, in vivo tumor volume changes with magnetic resonance imaging, and gross and histological analysis in a mouse model. The tumor volume continuously decreased over time in all IRE-treated groups. The tumor volume changes, necroptosis (%), necrosis (%), the degree of TUNEL-positive cell expression, and ROS1-positive cell (%) in the long pulse duration-treated groups (300 μs) were significantly increased compared to the short pulse duration-treated groups (100 μs) (all p < 0.001). The bipolar IRE with a relatively long pulse duration at the same voltage significantly increased IRE-induced cell death in a prostate cancer mouse model.

Holotomography and atomic force microscopy: a powerful combination to enhance cancer, microbiology and nanotoxicology research

Modern imaging strategies are paramount to studying living systems such as cells, bacteria, and fungi and their response to pathogens, toxicants, and nanomaterials (NMs) as modulated by exposure and environmental factors. The need to understand the processes and mechanisms of damage, healing, and cell survivability of living systems continues to motivate the development of alternative imaging strategies. Of particular interest is the use of label-free techniques (microscopy procedures that do not require sample staining) that minimize interference of biological processes by foreign marking substances and reduce intense light exposure and potential photo-toxicity effects. This review focuses on the synergic capabilities of atomic force microscopy (AFM) as a well-developed and robust imaging strategy with demonstrated applications to unravel intimate details in biomedical applications, with the label-free, fast, and enduring Holotomographic Microscopy (HTM) strategy. HTM is a technique that combines holography and tomography using a low intensity continuous illumination laser to investigate (quantitatively and non-invasively) cells, microorganisms, and thin tissue by generating three-dimensional (3D) images and monitoring in real-time inner morphological changes. We first review the operating principles that form the basis for the complementary details provided by these techniques regarding the surface and internal information provided by HTM and AFM, which are essential and complimentary for the development of several biomedical areas studying the interaction mechanisms of NMs with living organisms. First, AFM can provide superb resolution on surface morphology and biomechanical characterization. Second, the quantitative phase capabilities of HTM enable superb modeling and quantification of the volume, surface area, protein content, and mass density of the main components of cells and microorganisms, including the morphology of cells in microbiological systems. These capabilities result from directly quantifying refractive index changes without requiring fluorescent markers or chemicals. As such, HTM is ideal for long-term monitoring of living organisms in conditions close to their natural settings. We present a case-based review of the principal uses of both techniques and their essential contributions to nanomedicine and nanotoxicology (study of the harmful effects of NMs in living organisms), emphasizing cancer and infectious disease control. The synergic impact of the sequential use of these complementary strategies provides a clear drive for adopting these techniques as interdependent fundamental tools.

Effects of Nanosecond Pulsed Electric Field on Immune Checkpoint Receptors in Melanoma Cells

Checkpoint molecules such as PD-1, LAG-3, and TIM-3 are currently under extensive investigation for their roles in the attenuation of the immune response in cancer. Various methods have been applied to overcome the challenges in this field. This study investigated the effects of nanosecond pulsed electric field (nsPEF) treatment on the expression of immune checkpoint molecules in A375 and C32 melanoma cells. The researchers found that the nsPEF treatment was able to enhance membrane permeabilization and morphological changes in the cell membrane without being cytotoxic. We found that the effects of nsPEFs on melanoma included (1) the transport of vesicles from the inside to the outside of the cells, (2) cell contraction, and (3) the migration of lipids from inside the cells to their peripheries. The treatment increased the expression of PD-1 checkpoint receptors. Furthermore, we also observed potential co-localization or clustering of MHC class II and PD-1 molecules on the cell surface and the secretion of cytokines such as TNF-α and IL-6. These findings suggest that nsPEF treatment could be a viable approach to enhance the delivery of therapeutic agents to cancer cells and to modulate the tumor microenvironment to promote an antitumor immune response. Further studies are needed to explore the mechanisms underlying these effects and their impacts on the antitumor immune response, and to investigate the potential of nsPEF treatment in combination with immune checkpoint inhibitors to improve clinical outcomes for cancer patients.

Electrochemotherapy of Melanoma Cutaneous Metastases in Organ Transplant Recipients: A Systematic Review of Preclinical and Clinical Studies

Cutaneous melanoma is a highly aggressive form of skin cancer. The development of immune checkpoint inhibitors (ICIs) has revolutionized the management of advanced melanoma, led to durable responses, and improved overall survival. However, the success of ICIs in melanoma treatment is influenced by the tumor microenvironment (TME) which plays a critical role in regulating the immune response to the tumor. Understanding the mechanisms underlying this interaction is crucial to optimizing the efficiency of ICIs. Electrochemotherapy (ECT) has been shown to enhance the efficacy of ICIs in melanoma treatment by inducing tumor cell death and facilitating the release of tumor antigens which can subsequently be recognized and targeted by the immune system. Moreover, ECT has been reported to modulate the TME, leading to increased infiltration of immune cells and a more favorable immunological profile. In this review, we summarize the available knowledge of changes in TME after ECT of melanoma cutaneous metastasis and highlight the differences in tumor-infiltrating immune cells between immunocompetent and immunosuppressed organisms. In addition, we showed that ECT can be an effective and safe procedure for organ transplant recipients. Furthermore, repeated ECT may enhance immune activation and probably induce a bystander effect by trained immunity.

Electrostimulation improves plant growth and modulates the flavonoid profile in aeroponic culture of Scutellaria baicalensis Georgi

Scutellaria baicalensis Georgi is a valuable medicinal plant of the Lamiaceae family. The roots, Scutellariae baicalensis radix, are valued in the traditional medicine of East Asia and are also listed in several pharmacopeias, such as the Chinese and European versions. The roots contain a high amount of flavones, such as baicalein, wogonin and their glucuronides, baicalin and wogonoside, respectively, with rare structures of unsubstituted B-ring. These major constituents are responsible for its pharmacological activity, mainly anti-inflammatory, antiviral, and antitumor, as well as BDZ-receptor modulating. There is a fast-growing demand for both the crude drug and the individual flavonoids obtained from it. However, the variability of content and composition of flavonoids in the roots is significant and affects pharmaceutical use, and little is known about the influence of various factors on root quality. In our experiments, we use aeroponics to determine the effect of electroporation as an abiotic stressor on plant growth, development, and root mass, as well as on its metabolic profile.

RESULTS

Electroporation significantly impacted plant growth and the content of flavonoids, especially baicalein and wogonin, depending on the treatment parameters. Concentrations of aglycones were increased in at least half of the treatment conditions. The greatest amounts (a 2.5-fold increase compared to controls) were recorded after applying an electrical field characterized by the following parameters: E = 3 kV/cm, t = 100 μs, and N = 10. In conclusion, electrostimulation is an innovative and efficient way to increase plant growth and yield in an aeroponic system, as well as modulate the profile and content of bioactive flavones in the roots. However, the fine-tuning of these parameters, such as the electrical field strength (E), length (t), and number (N) of impulses delivered, is of great importance. It was also shown that cultivation of the experimental plants in aeroponics had a positive impact on their survival and development while being a sustainable and efficient horticultural practice.

Nanosecond pulsed electric field suppresses growth and reduces multi-drug resistance effect in pancreatic cancer

Nanosecond pulsed electric fields (nsPEF) have been shown to exert anticancer effects; however, little is known about the mechanisms triggered in cancer cells by nanosecond-length pulses, especially when low, sub-permeabilization voltage is used. In this study, three human pancreatic cancer cell lines were treated with nsPEF and molecular changes at the cellular level were analyzed. Further, we assessed the efficacy of paclitaxel chemotherapy following nsPEF treatment and correlated that with the changes in the expression of multi-drug resistance (MDR) proteins. Finally, we examined the influence of nsPEF on the adhesive properties of cancer cells as well as the formation and growth of pancreatic cancer spheroids. Cell line response differed with the application of a 200 ns, 100 pulses, 8 kV/cm, 10 kHz PEF treatment. PEF treatment led to (1) the release of microvesicles (MV) in EPP85-181RDB cells, (2) electropermeabilization in EPP85-181RNOV cells and (3) cell shrinkage in EPP85-181P cells. The release of MV's in EPP85-181RDB cells reduced the membrane content of P-gp and LRP, leading to a transient increase in vulnerability of the cells towards paclitaxel. In all cell lines we observed an initial reduction in size of the cancer spheroids after the nsPEF treatment. Cell line EPP85-181RNOV exhibited a permanent reduction in the spheroid size after nsPEF. We propose a mechanism in which the surface tension of the membrane, regulated by the organization of actin fibers, modulates the response of cancer cells towards nsPEF. When a membrane's surface tension remains low, we observed some cells form protrusions and release MVs containing MDR proteins. In contrast, when cell surface tension remains high, the cell membrane is being electroporated. The latter effect may be responsible for the reduced tumor growth following nsPEF treatment.

Enhanced Therapeutic Potential of Irreversible Electroporation under Combination with Gold-Doped Mesoporous Silica Nanoparticles against EMT-6 Breast Cancer Cells

Irreversible electroporation (IRE) is a non-thermal tumor ablation technique that delivers short pulses of strong electric fields to cancer tissues and induces cell death through the destruction of cell membranes. Here, we synthesized gold-doped mesoporous silica nanoparticles (Au-MSNs) via incipient wetness impregnation and evaluated the therapeutic potentials of combination therapy with IRE. The fabricated Au-MSNs had around 80-100 nm of particle size and were successfully end-doped with Au nanoparticles. Combination treatment of IRE (800 V/cm) and Au-MSNs (100 μg/mL) increased cell membrane permeability by 25-fold compared with single IRE treatment. Cellular reactive oxygen species (ROS) and lipid peroxidation of EMT-6 cells were significantly increased by 14- and 265-fold, respectively, under combination treatment of IRE (800 V/cm) and Au-MSNs (100 µg/mL). Cytotoxic cell death increased by 28% under a combination treatment of IRE (800 V/cm) and Au-MSNs (100 ug/mL) over single IRE. Our studies suggest that the combination treatment of IRE with Au-MSNs can enhance the therapeutic efficacy of IRE for breast cancer.

Pulsed electric fields with calcium ions stimulate oxidative alternations and lipid peroxidation in human non-small cell lung cancer

Pulsed electric fields (PEFs) are commonly used to facilitate the delivery of various molecules, including pharmaceuticals, into living cells. However, the applied protocols still require optimization regarding the conditions of the permeabilization process, i.e., pulse waveform, voltage, duration, and the number of pulses in a burst. This study highlights the importance of electrochemical processes involved in the electropermeabilization process, known as electroporation. This research investigated the effects of electroporation on human non-small cell lung cancer cells (A549) in potassium (SKM) and HEPES-based buffers (SHM) using sub-microsecond and microsecond range pulses. The experiments were performed using 100 ns - 100 μs (0.6-15 kV/cm) bursts with 8 pulses in a sequence. It was shown that depending on the buffer composition, the susceptibility of cells to PEF varies, while calcium enhances the cytotoxic effects of PEF, if high cell membrane permeabilization is triggered. It was also determined that electroporation with calcium ions induces oxidative stress in cells, including lipid peroxidation (LPO), generation of reactive oxygen species (ROS), and neutral lipid droplets. Here, we demonstrated that calcium ions and optimized pulse parameters could potentiate PEF efficacy and oxidative alternations in lung cancer cells. Thus, the anticancer efficacy of PEF in lung cancers in combination with standard cytostatic drugs or calcium ions should be considered, but this issue still requires in-depth detailed studies with in vivo models.

Combined In Vitro Toxicity and Immunogenicity of Cold Plasma and Pulsed Electric Fields

In modern oncology, therapies are based on combining monotherapies to overcome treatment resistance and increase therapy precision. The application of microsecond-pulsed electric fields (PEF) is approved to enhance local chemotherapeutic drug uptake within combination electrochemotherapy regimens. Reactive oxygen species (ROS) have been implicated in anticancer effects, and cold physical plasma produces vast amounts of ROS, which have recently been shown to benefit head and neck cancer patients. PEF and cold plasma technology have been linked to immunogenic cell death (ICD) induction, a regulated cell death accompanied by sterile inflammation that promotes antitumor immunity. To this end, we investigated the combined effect of both treatments regarding their intracellular ROS accumulation, toxicity, ICD-related marker expression, and optimal exposure sequence in a leukemia model cell line. The combination treatment substantially increased ROS and intracellular glutathione levels, leading to additive cytotoxic effects accompanied by a significantly increased expression of ICD markers, such as the eat-me signal calreticulin (CRT). Preconditioned treatment with cold plasma followed by PEF exposure was the most potent treatment sequence. The results indicate additive effects of cold plasma and PEF, motivating further studies in skin and breast tumor models for the future improvement of ECT in such patients.

High-Intensity Pulsed Electromagnetic Field-Mediated Gene Electrotransfection In Vitro

A high-intensity pulsed electromagnetic field (HI-PEMF) is a non-invasive and non-contact delivery method and may, as such, have an advantage over gene electrotransfer mediated by conventional electroporation using contact electrodes. Due to the limited number of in vitro studies in the field of gene electrotransfection by HI-PEMF, we designed experiments to investigate and demonstrate the feasibility of such a technique for the non-viral delivery of genetic material into cells in vitro. We first showed that HI-PEMF causes DNA adsorption to the membrane, a generally accepted prerequisite step for successful gene electrotransfection. We also showed that HI-PEMF can induce gene electrotransfection as the application of HI-PEMF increased the percentage of GFP-positive cells for two different combinations of pDNA size and concentration. Furthermore, by measuring the uptake of larger molecules, i.e., fluorescently labelled dextrans of three different sizes, we showed endocytosis to be a possible mechanism for introducing large molecules into cells by HI-PEMF.

Effect of pulsed field ablation on solid tumor cells and microenvironment

Pulsed field ablation can increase membrane permeability and is an emerging non-thermal ablation. While ablating tumor tissues, electrical pulses not only act on the membrane structure of cells to cause irreversible electroporation, but also convert tumors into an immune active state, increase the permeability of microvessels, inhibit the proliferation of pathological blood vessels, and soften the extracellular matrix thereby inhibiting infiltrative tumor growth. Electrical pulses can alter the tumor microenvironment, making the inhibitory effect on the tumor not limited to short-term killing, but mobilizing the collective immune system to inhibit tumor growth and invasion together.

Scanning electrochemical microscopy based irreversible destruction of living cells

In this research, scanning electrochemical microscopy combined with electrochemical impedance spectroscopy has been applied to irreversible electroporation of active yeast cells by causing cell death. This finding is important for the development of irreversible electroporation technique, which could be suitable for the curing of cancerous tissues, because during this research cell death has been achieved using relatively low ultramicro-electrode (UME) voltage, precisely of 2.0 V vs Ag/AgCl,Cl^-sat. It was determined that the irreversibly electroporated area of immobilized yeast cells was located directly below the UME and was of approximately 20 times larger width than the diameter of the UME, leaving undamaged cells out of this area. The ability of SECM to move the UME with high accuracy in x, y, and z directions and the ability to use electrodes of various diameters as well as the fact that the diameter of the electroporated area depends on the diameter of the UME and on the distance between the UME and the surface, what offers the possibility to establish targeted electroporation systems for selective treatment of tissues.

Nanosecond electric pulses are equally effective in electrochemotherapy with cisplatin as microsecond pulses

BACKGROUND

Nanosecond electric pulses showed promising results in electrochemotherapy, but the underlying mechanisms of action are still unexplored. The aim of this work was to correlate cellular cisplatin amount with cell survival of cells electroporated with nanosecond or standardly used 8 × 100 μs pulses and to investigate the effects of electric pulses on cisplatin structure.

MATERIALS AND METHODS

Chinese hamster ovary CHO and mouse melanoma B16F1 cells were exposed to 1 × 200 ns pulse at 12.6 kV/cm or 25 × 400 ns pulses at 3.9 kV/cm, 10 Hz repetition rate or 8 × 100 μs pulses at 1.1 (CHO) or 0.9 (B16F1) kV/cm, 1 Hz repetition rate at three cisplatin concentrations. Cell survival was determined by the clonogenic assay, cellular platinum was measured by inductively coupled plasma mass spectrometry. Effects on the structure of cisplatin were investigated by nuclear magnetic resonance spectroscopy and high-resolution mass spectrometry.

RESULTS

Nanosecond pulses equivalent to 8 × 100 μs pulses were established in vitro based on membrane permeabilization and cell survival. Equivalent nanosecond pulses were equally efficient in decreasing the cell survival and accumulating cisplatin intracellularly as 8 × 100 μs pulses after electrochemotherapy. The number of intracellular cisplatin molecules strongly correlates with cell survival for B16F1 cells, but less for CHO cells, implying the possible involvement of other mechanisms in electrochemotherapy. The high-voltage electric pulses did not alter the structure of cisplatin.

CONCLUSIONS

Equivalent nanosecond pulses are equally effective in electrochemotherapy as standardly used 8 × 100 μs pulses.

Chemotherapy and Physical Therapeutics Modulate Antigens on Cancer Cells

Cancer cells possess specific properties, such as multidrug resistance or unlimited proliferation potential, due to the presence of specific proteins on their cell membranes. The release of proliferation-related proteins from the membrane can evoke a loss of adaptive ability in cancer cells and thus enhance the effects of anticancer therapy. The upregulation of cancer-specific membrane antigens results in a better outcome of immunotherapy. Moreover, cytotoxic T-cells may also become more effective when stimulated ex-vivo toward the anticancer response. Therefore, the modulation of membrane proteins may serve as an interesting attempt in anticancer therapy. The presence of membrane antigens relies on various physical factors such as temperature, exposure to radiation, or drugs. Therefore, changing the tumor microenvironment conditions may lead to cancer cells becoming sensitized to subsequent therapy. This paper focuses on the therapeutic approaches modulating membrane antigens and enzymes in anticancer therapy. It aims to analyze the possible methods for modulating the antigens, such as pharmacological treatment, electric field treatment, photodynamic reaction, treatment with magnetic field or X-ray radiation. Besides, an overview of the effects of chemotherapy and immunotherapy on the immunophenotype of cancer cells is presented. Finally, the authors review the clinical trials that involved the modulation of cell immunophenotype in anticancer therapy.

NK and cells with NK-like activities in cancer immunotherapy-clinical perspectives

Natural killer (NK) cells are lymphoid cells of innate immunity that take important roles in immune surveillance. NK cells are considered as a bridge between innate and adaptive immunity, and their infiltration into tumor area is related positively with prolonged patient survival. They are defined as CD16⁺ CD56⁺ CD3^- cells in clinic. NK cells promote cytolytic effects on target cells and induce their apoptosis. Loss of NK cell cytotoxic activity and reduction in the number of activating receptors are the current issues for application of such cells in cellular immunotherapy, which resulted in the diminished long-term effects. The focus of this review is to discuss about the activity of NK cells and cells with NK-like activity including natural killer T (NKT), cytokine-induced killer (CIK) and lymphokine-activated killer (LAK) cells in immunotherapy of human solid cancers.

Micro- and Nanosecond Pulses Used in Doxorubicin Electrochemotherapy in Human Breast and Colon Cancer Cells with Drug Resistance

(1) Background: Pulsed electric field (PEF) techniques are commonly used to support the delivery of various molecules. A PEF seems a promising method for low permeability drugs or when cells demonstrate therapy resistance and the cell membrane becomes an impermeable barrier. (2) Methods: In this study, we have used doxorubicin-resistant and sensitive models of human breast cancer (MCF-7/DX, MCF-7/WT) and colon cancer cells (LoVo, LoVoDX). The study aimed to investigate the susceptibility of the cells to doxorubicin (DOX) and electric fields in the 20–900 ns pulse duration range. The viability assay was utilized to evaluate the PEF protocols’ efficacy. Cell confluency and reduced glutathione were measured after PEF protocols. (3) Results: The obtained results showed that PEFs significantly supported doxorubicin delivery and cytotoxicity after 48 and 72 h. The 60 kV/cm ultrashort pulses × 20 ns × 400 had the most significant cytotoxic anticancer effect. The increase in DOX concentration provokes a decrease in cell viability, affected cell confluency, and reduced GSSH when combined with the ESOPE (European Standard Operating Procedures of Electrochemotherapy) protocol. Additionally, reactive oxygen species after PEF and PEF-DOX were detected. (4) Conclusions: Ultrashort electric pulses with low DOX content or ESOPE with higher DOX content seem the most promising in colon and breast cancer treatment.

Feasibility of Concentric Electrodes in Contact Irreversible Electroporation for Superficial Lesion Treatment

<i>Objective:</i> Contact irreversible electroporation (IRE) is a method for ablating cells by applying electric pulses via surface electrodes in contact with a target tissue. To facilitate the application of the contact IRE to superficial lesion treatment, this study further extended the ablation depth, which had been limited to a 400-m depth in our previous study, by using concentric electrodes. <i>Methods:</i> A prototype device of concentric electrodes was manufactured using a Teflon-coated copper wire inserted in a copper tube. The ablation area was experimentally determined using a tissue phantom comprising 3D cultured fibroblasts and compared with the electric field distribution obtained using numerical analyses. </i>Results:</i> Experiments showed that cells 540 m from the surface of the tissue phantom were necrotized by the application of 150 pulses at 100 V. The outline of the ablation area agreed well with the contour line of 0.4 kV/cm acquired by the analyses. The ablation depth predicted for the concentric electrode using this critical electric field was 1.4 times deeper than that for the parallel electrode. For the actual application of treatment, a multiple-electrode device that bundles several pairs of concentric electrodes was developed, and confirmed that to be effective for treating wide areas with a single treatment. <i>Conclusion:</i> The electric field estimated by the analyses with the experimentally determined threshold confirmed that concentric electrodes could attain a deeper ablation than parallel electrodes. <i>Significance:</i> Using the concentric electrodes, we were able to localize ablation to specific target cells with much less damage to neighboring cells.

ROS Pleiotropy in Melanoma and Local Therapy with Physical Modalities

Metabolic energy production naturally generates unwanted products such as reactive oxygen species (ROS), causing oxidative damage. Oxidative damage has been linked to several pathologies, including diabetes, premature aging, neurodegenerative diseases, and cancer. ROS were therefore originally anticipated as an imperative evil, a product of an imperfect system. More recently, however, the role of ROS in signaling and tumor treatment is increasingly acknowledged. This review addresses the main types, sources, and pathways of ROS in melanoma by linking their pleiotropic roles in antioxidant and oxidant regulation, hypoxia, metabolism, and cell death. In addition, the implications of ROS in various physical therapy modalities targeting melanoma, such as radiotherapy, electrochemotherapy, hyperthermia, photodynamic therapy, and medical gas plasma, are also discussed. By including ROS in the main picture of melanoma skin cancer and as an integral part of cancer therapies, a greater understanding of melanoma cell biology is presented, which ultimately may elucidate additional clues on targeting therapy resistance of this most deadly form of skin cancer.

The Evidence of the Bystander Effect after Bleomycin Electrotransfer and Irreversible Electroporation

One of current applications of electroporation is electrochemotherapy and electroablation for local cancer treatment. Both of these electroporation modalities share some similarities with radiation therapy, one of which could be the bystander effect. In this study, we aimed to investigate the role of the bystander effect following these electroporation-based treatments. During direct CHO-K1 cell treatment, cells were electroporated using one 100 µs duration square wave electric pulse at 1400 V/cm (for bleomycin electrotransfer) or 2800 V/cm (for irreversible electroporation). To evaluate the bystander effect, the medium was taken from directly treated cells after 24 h incubation and applied on unaffected cells. Six days after the treatment, cell viability and colony sizes were evaluated using the cell colony formation assay. The results showed that the bystander effect after bleomycin electrotransfer had a strong negative impact on cell viability and cell colony size, which decreased to 2.8% and 23.1%, respectively. On the contrary, irreversible electroporation induced a strong positive bystander effect on cell viability, which increased to 149.3%. In conclusion, the results presented may serve as a platform for further analysis of the bystander effect after electroporation-based therapies and may ultimately lead to refined application of these therapies in clinics.

Effects of high-frequency nanosecond pulses on prostate cancer cells

Electroporation with pulsed electric fields show a potential to be applied as an experimental focal therapy of tumors. Sub-microsecond regime of electric pulses displays unique electrophysical features operative in cells and membranes. Recently, MHz compression of nanosecond pulses electric fields (nsPEFs) bursts proved to enhance the effectiveness of the therapy. High morbidity of prostate cancer (PCa) and risk of overtreatment associated with this malignancy call for new minimal-invasive treatment alternative. Herein we present the in vitro study for developing applications based on this new technology. In this study, we used flow cytometric analysis, cell viability assay, caspase activity analysis, wound healing assay, confocal microscopy study, and immunofluorescence to investigate the biological effect of high-frequency nsPEFs on PCa cells. Our results show that high-frequency nsPEFs induces the permeabilization and cell death of PCa cells. The cytotoxicity is significantly enhanced in MHz compression of pulses and with the presence of extracellular Ca²⁺. High-frequency nsPEFs trigger changes in PCa cells' cytoskeleton and their mobility. The presented data show a therapeutic potential of high-frequency nsPEFs in a PCa setting. The sub-microsecond regime of pulses can potentially be applied in nanosecond electroporation protocols for PCa treatment.

Dielectrophoretic Manipulation of Cell Transfection Efficiency during Electroporation Using a Center Needle Electrode

Long duration electric pulses are frequently used to facilitate DNA electrotransfer into cells and tissues, while electroporation pulses can be combined with electrophoresis to maximize the transfection efficiency. In this work, we present the dielectrophoresis (DEP)-assisted methodology for electrotransfer of plasmid DNA (3.5 kbp pmaxGFP) into mammalian cells (CHO-K1). A prototype of an electroporation cuvette with center needle electrode for DEP-assisted transfection is presented resulting in a 1.4-fold of transfection efficiency increase compared to the electroporation-only procedure (1.4 kV/cm × 100 µs × 8). The efficiency of transfection has been compared between three DEP frequencies of 1, 100, and 1 MHz. Lastly, the effects of exposure time (1, 3, and 5 min) during the DEP application step have been determined. It is concluded that the proposed methodology and exposure setup allow a significant improvement of transfection efficiency and could be used as an alternative to the currently popular electrotransfection techniques.

Cell death due to electroporation - A review

Exposure of cells to high voltage electric pulses increases transiently membrane permeability through membrane electroporation. Electroporation can be reversible and is used in gene transfer and enhanced drug delivery but can also lead to cell death. Electroporation resulting in cell death (termed as irreversible electroporation) has been successfully used as a new non-thermal ablation method of soft tissue such as tumours or arrhythmogenic heart tissue. Even though the mechanisms of cell death can influence the outcome of electroporation-based treatments due to use of different electric pulse parameters and conditions, these are not elucidated yet. We review the mechanisms of cell death after electroporation reported in literature, cell injuries that may lead to cell death after electroporation and membrane repair mechanisms involved. The knowledge of membrane repair and cell death mechanisms after cell exposure to electric pulses, targets of electric field in cells need to be identified to optimize existing and develop of new electroporation-based techniques used in medicine, biotechnology, and food technology.