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In recent years, pulsed magnetic field (PMF) have attracted significant attention as a non-invasive electroporation method in the biomedical field. To further explore the biomedical effects generated by oscillating PMF, we designed a novel PMF generator for biomedical research. Based on resonance principles, the designed generator outputs sinusoidal oscillating PMF. To validate the feasibility and application value of the designed topology, a miniaturized platform was constructed using a selected multi-turn solenoid coil. The output performance of the generator was tested under different discharge voltage levels. The results revealed that the current multiplication factor remained consistently around 2 times, with the energy efficiency and circuit quality factor maintained at 82% and above 4.5, respectively. In addition, the generator's ability to flexibly modulate the number of pulse oscillations was demonstrated. The compatibility of the designed coil parameters and generator circuit parameters was analyzed, with tests on the effects of coil resistance and switch action time on the generator's output performance. Based on the magnetic field action platform, a simulation model of the actual scale coil was established. The spatial and temporal distribution of the magnetic field, induced electric field, and power transmission in the target area were described from multiple angles. Finally, biological experiments conducted using the constructed generator revealed the synergistic effect of sinusoidal oscillating PMF combined with drugs in tumor cell killing.

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With the introduction of nanosecond (ns) pulses, it was suggested that such pulses could be used to permeabilize intracellular membranes, including the mitochondrial membrane. The results presented thus far, however, are not conclusive. Interestingly, the effect of longer microsecond (µs) pulses on changes in mitochondria has never been investigated. We, therefore, investigated the changes in mitochondrial membrane permeability through changes in mitochondrial membrane potential (MMP) in CHO and H9c2 cells after electroporation with 4 ns, 200 ns, and 100 µs pulses. In the range of reversible electroporation, the decrease in MMP generally depended on the cell line. In CHO, ns pulses decreased MMP at lower electroporation intensities than µs. In H9c2, ns and µs were equally effective. In the range of irreversible electroporation, MMP decreased even further, regardless of pulse duration and cell type. The analysis at different time points showed that the changes in MMP within the first hour after pulse treatment are dynamic. Our results on the efficacy of ns pulses are consistent with published data, but with this study we show that µs pulses cause similar changes in MMP as ns pulses, demonstrating that electroporation affects MMP regardless of pulse duration. At the same time, however, differences in MMP changes were observed between different cell lines, indicating some dependence of MMP changes on cell type.

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Irreversible electroporation (IRE) has emerged as a promising modality for tumor ablation, leveraging the controlled application of electrical pulses to induce cell death. However, the associated muscle contractions during the procedure pose challenges. This study introduces a novel approach, termed Synergistic Bipolar Irreversible Electroporation (SBIRE), aimed at achieving tumor ablation without the undesirable side effect of muscle contraction. SBIRE involves the simultaneous application of nanosecond bipolar electrical pulses (±1600 V per 0.2 cm or ±8000 V per 1 cm, ±500 ns, "+" to "-" delay 1 µs, "-" to "+" delay 200 µs, 5 cycles) and microsecond bipolar electrical pulses (±300 V per 0.2 cm or ±1500 V per 1 cm, ±2 µs, "+" to "-" delay 2 µs, "-" to "+" delay 1000 µs, 25 cycles), strategically designed to synergistically target tumor cells while minimizing the impact on adjacent muscle tissue. The experimental setup includes in vitro and in vivo studies utilizing tumor cells and animal models to assess the efficacy of SBIRE. Preliminary results demonstrate the effectiveness of SBIRE in inducing irreversible electroporation within the tumor, leading to cell death, and the ablation effect is better than other parameter forms (24.41±0.23 mm2 (SBIRE group) vs 12.93±0.31 mm2 (ns group), 6.55±0.23 mm2 (µs group), 19.54±0.25 mm2 (ns+µs group), p<0.0001). Notably, muscle contraction is significantly reduced compared to traditional IRE procedures, highlighting the potential of SBIRE to enhance patient comfort and procedural success. The development of SBIRE represents a significant advancement in the field of tumor ablation, addressing a fundamental limitation associated with muscle contraction during IRE. This technique not only offers a valuable and promising approach to tumor treatment but also holds promise for minimizing procedural side effects.

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Patients diagnosed with glioma typically face a limited life expectancy (around 15 months on average), a bleak prognosis, and a high likelihood of recurrence. As such, glioma is recognized as a significant form of malignancy. Presently, the treatment options for glioma include traditional approaches such as surgery, chemotherapy, and radiotherapy. Regrettably, the efficacy of these treatments has been less than optimal. Nevertheless, a promising development in glioma treatment lies in the use of hydrogel nano-systems as sophisticated delivery systems. These nano-systems have demonstrated exceptional therapeutic effects in the treatment of glioma by various responsive ways, including temperature-response, pH-response, liposome-response, ROS-response, light-response, and enzyme-response. This study seeks to provide a comprehensive summary of both the therapeutic application of hydrogel nano-systems in managing glioma and the underlying immune action mechanisms.

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The cellular membrane serves as a pivotal barrier in regulating intra- and extracellular matter exchange. Disruption of this barrier through pulsed electric fields (PEFs) induces the transmembrane transport of ions and molecules, creating a concentration gradient that subsequently results in the imbalance of cellular osmolality. In this study, a multiphysics model was developed to simulate the electromechanical response of cells exposed to microsecond pulsed electric fields (µsPEFs). Within the proposed model, the diffusion coefficient of the cellular membrane for various ions was adjusted based on electropore density. Cellular osmolality was governed and described using Van't Hoff theory, subsequently converted to loop stress to dynamically represent the cell swelling process. Validation of the model was conducted through a hypotonic experiment and simulation at 200 mOsm/kg, revealing a 14.2% increase in the cell's equivalent radius, thereby confirming the feasibility of the cell mechanical model. With the transmembrane transport of ions induced by the applied µsPEF, the hoop stress acting on the cellular membrane reached 179.95 Pa, and the cell equivalent radius increased by 11.0% when the extra-cellular medium was supplied with normal saline. The multiphysics model established in this study accurately predicts the dynamic changes in cell volume resulting from osmotic imbalance induced by PEF action. This model holds theoretical significance, offering valuable references for research on drug delivery and tumor microenvironment modulation.

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The mechanisms of cell death due to electroporation are still not well understood. Recent studies suggest that cell death due to electroporation is not an immediate all-or-nothing response but rather a dynamic process that occurs over a prolonged period of time. To investigate whether the dynamics of cell death depends on the pulse parameters or cell lines, we exposed different cell lines to different pulses [monopolar millisecond, microsecond, nanosecond, and high-frequency bipolar (HFIRE)] and then assessed viability at different times using different viability assays. The dynamics of cell death was observed by changes in metabolic activity and membrane integrity. In addition, regardless of pulse or cell line, the dynamics of cell death was observed only at high electroporation intensities, i.e., high pulse amplitudes and/or pulse number. Considering the dynamics of cell death, the clonogenic assay should remain the preferred viability assay for assessing viability after electroporation.

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In this work, we proposed nµPEF, a novel pulse configuration combining nanosecond and microsecond pulses (nµPEF), to enhance tumor ablation in irreversible electroporation (IRE) for oncological therapy. nµPEF demonstrated improved efficacy in inducing immunogenic cell death, positioning it as a potential candidate for next-generation ablative therapy. However, the immune response elicited by nµPEF alone was insufficient to effectively suppress distant tumors. To address this limitation, we developed PPR@CM-PD1, a genetically engineered nanovesicle. PPR@CM-PD1 employed a polyethylene glycol-polylactic acid-glycolic acid (PEG-PLGA) nanoparticle encapsulating the immune adjuvant imiquimod and coated with a genetically engineered cell membrane expressing programmed cell death protein 1 (PD1). This design allowed PPR@CM-PD1 to target both the innate immune system through toll-like receptor 7 (TLR7) agonism and the adaptive immune system through programmed cell death protein 1/programmed cell death-ligand 1 (PD1/PDL1) checkpoint blockade. In turn, nµPEF facilitated intratumoral infiltration of PPR@CM-PD1 by modulating the tumor stroma. The combination of nµPEF and PPR@CM-PD1 generated a potent and systemic antitumor immune response, resulting in remarkable suppression of both nµPEF-treated and untreated distant tumors (abscopal effects). This interdisciplinary approach presents a promising perspective for oncotherapy and holds great potential for future clinical applications.

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The H-FIRE (high-frequency irreversible electroporation) protocol employs high-frequency bipolar pulses (HFBPs) with a width of ∼1 µs for tumor ablation with slight muscle contraction. However, H-FIRE pulses need a higher electric field to generate a sufficient ablation effect, which may cause undesirable thermal damage. OBJECTIVE: Recently, combining short high-voltage IRE monopolar pulses with long low-voltage IRE monopolar pulses was shown to enlarge the ablation region. This finding indicates that combining HFBPs with low-voltage bipolar pulses (LVBPs), which are called composited bipolar pulses (CBPs), may enhance the ablation effect. METHODS: This study designed a pulse generator by modifying a full-bridge inverter. The cell suspension and 3D tumor mimic experiments (U251 cells) were performed to examine the enhancement of the ablation effect. RESULTS: The generator outputs HFBPs with 0-±2.5 kV and LVBPs with 0-±0.3 kV in one period. The pulse parameters are adjustable by programming on a human-computer interface. The cell suspension experiments showed that CBPs could enhance cytotoxicity, as compared to HFBPs with no cell-killing effect. Even at lower electric energy, the cell viability by CBPs was significantly lower than that of the HFBPs protocol. The ablation experiments on the 3D tumor mimic showed that the CBPs could create a larger connected ablation area. In contrast, the HFBPs protocol with a similar dose generated a nonconnected ablation area. CONCLUSION: Results indicate that the CBPs protocol can enhance the ablation effect of HFBPs protocol. SIGNIFICANCE: This proposed generator that uses the CBPs principle may be a useful tool for tumor ablation.

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Insufficient surface insulation margin is the primary challenge for a 10 kV plus high-voltage semiconductor module. Surface charge accumulation and electric field distortion are the leading causes of surface insulation failure. Power modules restrict leakage loss, so only insulation dielectrics with low surface conductivity can be used. However, low conductivity, accumulated charge dissipation, and distorted electric field optimization have always been contradictory. A potential barrier increase and electron affinity decrease are both less coupled approaches with conductivity, which may have the potential for reducing surface charge accumulation. Here, surface charge accumulation inhibition and local electric field optimization were synchronously realized by tailored coating deposition with colliding plasma jets. This novelty approach leads to a finer interfacial modification of the triple junction and its nearby interfaces. The high-barrier and low-affinity coatings deposited by colliding plasma jets suppress charge injection (electrode-polymer interface) and promote charge dissipation (gas-polymer interface), respectively. At the same time, the small-area semiconductor deposited at the triple junction relieves the distortion of the electric field. In the end, while maintaining a low leakage current, the surface flashover voltages of polytetrafluoroethylene, polyimide, and epoxy packaging polymers are significantly increased by 69.7, 43.2, and 39.6%, respectively. Notably, the normalized leakage loss is less than 3/10,000 of the commercially available SiC module, which vastly differs from the surface insulation improvement strategy that blindly increases surface conductivity. This tailored coating modification strategy provides a new idea for dielectric research. It has reasonable practicability due to fast, cheap, and environmentally friendly colliding plasma jets.

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Precise control of cargo release is essential but still a great challenge for any drug delivery system. Irreversible electroporation (IRE), utilizing short high-voltage pulsed electric fields to destabilize the biological membrane, has been recently approved as a non-thermal technique for tumor ablation without destroying the integrity of adjacent collagenous structures. Due to the electro-permeating membrane ability, IRE might also have great potential to realize the controlled drug release in response to various input IRE parameters, which were tested in a red blood cell (RBC) model in this work. According to the mathematical simulation model of a round biconcave disc-like cell based on RBC shape and dielectric characteristics, the permeability and the pore density of the RBC membrane were found to quantitatively depend on the pulse parameters. To further provide solid experimental evidence, indocyanine green (ICG) and doxorubicin (DOX) were both loaded inside RBCs (RBC@DOX&ICG) and the drug release rates were found to be tailorable by microsecond pulsed electric field (µsPEF). In addition, µsPEF could effectively modulate the tumor stroma to augment therapy efficacy by increasing micro-vessel density and permeability, softening extracellular matrix, and alleviating tumor hypoxia. Benefiting from these advantages, this IRE-responsive RBC@DOX&ICG achieved a remarkably synergistic anti-cancer effect by the combination of µsPEF and chemotherapy in the tumor-bearing mice model, with the survival time increasing above 90 days without tumor burden. Given that IRE is easily adaptable to different plasma membrane-based vehicles for delivering diverse drugs, this approach could offer a general applicability for cancer treatment.

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Hundreds of high frequency bipolar pulse bursts with ∼1 µs have been suggested to alleviate muscle contractions and pain during the irreversible electroporation (IRE) tumor treatment. This study is performed to verify whether eight bursts of high frequency reversible electroporation pulses (HFREs) with bleomycin could be used for electrochemotherapy (ECT) tumor treatment. Firstly, in vitro experiments on B16 cells are performed to determine the cytotoxicity of the HFREs with bleomycin. The result indicates that the protocol of HFREs with bleomycin has a significant killing effect compared with only bleomycin, in which the used HFRE pulses are set to induce high membrane permeabilization while maintaining high cell viability. The immunogenic cell death (ICD) that generates danger associated molecular patterns (DAMPs) could trigger an adaptive immune response against tumors. We demonstrated that HFREs with bleomycin could trigger the hallmarks of ICD with obvious up-regulation of DAMPs, including ATP, HMGB1, and CRT. The ICD process may begin at 3 h but perform at 6 h after HFREs with bleomycin stimulation. The in vivo experiment on mice tumor treatment also showed that the protocol of HFREs with bleomycin could inhibit tumor growth with more cytotoxic CD8+ T cells infiltration. The results obtained from in vitro and in vitro experiments preliminary confirmed that the HFREs with bleomycin could be used for ECT tumor treatment associated with the hallmarks of ICD and preliminary trigger the adaptive immune response.

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Irreversible electroporation (IRE) by high-strength electric pulses is a biomedical technique that has been effectively used for minimally invasive tumor therapy while maintaining the functionality of adjacent important tissues, such as blood vessels and nerves. In general, pulse delivery using needle electrodes can create a reversible electroporation region beyond both the ablation area and the vicinity of the needle electrodes, limiting enlargement of the ablation area. Electrochemical therapy (EChT) can also be used to ablate a tumor near electrodes by electrolysis using a direct field with a constant current or voltage (DC field). Recently, reversible electroporated cells have been shown to be susceptible to electrolysis at relatively low doses. Reversible electroporation can also be combined with electrolysis for tissue ablation. Therefore, the objective of this study is to use electrolysis to remove the reversible electroporation area and thereby enlarge the ablation area in potato slices in vitro using a pulsed field with a bias DC field (constant voltage). We call this protocol electrolytic irreversible electroporation (E-IRE). The area over which the electrolytic effect induced a pH change was also measured. The results show that decreasing the pulse frequency using IRE alone is found to enlarge the ablation area. The ablation area generated by E-IRE is significantly larger than that generated by using IRE or EChT alone. The ablation area generated by E-IRE at 1 Hz is 109.5% larger than that generated by IRE, showing that the reversible electroporation region is transformed into an ablation region by electrolysis. The area with a pH change produced by E-IRE is larger than that produced by EChT alone. Decreasing the pulse frequency in the E-IRE protocol can further enlarge the ablation area. The results of this study are a preliminary indication that the E-IRE protocol can effectively enlarge the ablation area and enhance the efficacy of traditional IRE for use in ablating large tumors.

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Electroporation achieved by the application of pulsed electric field is successfully used for clinical tumor ablation. Electrochemotherapy (ECT) and irreversible electroporation (IRE), which are two protocols based on electroporation, have been shown to ablate only tumor cells while preserving the function of normal blood vessels. However, the mechanism of this unique advantage is still not fully understood. This study first built a multilayer dielectric model of both normal and tumor blood vessels to study the electroporation effect. Since endothelial cells are the main component of normal and tumor blood vessels, this study mainly analyzed the electroporation effect on endothelial cells. The rich vascular smooth muscle cells (VSMCs), could play a protective function, allowing endothelial cells to suffer less electroporation effect in normal blood vessels. Interestingly, the endothelial cells in tumor blood vessel sustained a stronger electroporation effect than those in normal blood vessels due to the lack of VSMCs. This study may provide a conceivable explanation for why the structure of endothelial cells in normal blood vessels is preserved during electroporation treatment. This study also demonstrates that ECT or IRE may also damage both tumor blood vessels and cells while preserving normal blood vessels, which benefits complete tumor ablation.

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Nanosecond pulsed electric fields (nsPEFs) may induce differential effects on tumor cells from different disease stages and could be suitable for treating tumors by preferentially targeting the late-stage/highly aggressive tumor cells. In this study, we investigated the nsPEF responses of mouse ovarian surface epithelial (MOSE) cells representing progressive ovarian cancer from benign to malignant stages and highly aggressive tumor-initiating-like cells. We established the cell-seeded 3D collagen scaffolds cultured with or without Nocodazole (eliminating the influence of cell proliferation on ablation outcome) to observe the ablation effects at 3 h and 24 h after treatment and compared the corresponding thresholds obtained by numerically calculated electric field distribution. The results showed that nsPEFs induced larger ablation areas with lower thresholds as the cell progress from benign, malignant to a highly aggressive phenotype. This differential effect was not affected by the different doubling times of the cells, as apparent by similar ablation induction after a synergistic treatment of nsPEFs and Nocodazole. The result suggests that nsPEFs could induce preferential ablation effects on highly aggressive and malignant ovarian cancer cells than their benign counterparts. This study provides an experimental basis for the research on killing malignant tumor cells via electrical treatments and may have clinical implications for treating tumors and preventing tumor recurrence after treatment.

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Chemoresistance causes tumor recurrence and metastasis, resulting in poor clinical outcomes and low survival, and has been considered an obstacle to tumor therapy. The development of novel therapeutic approaches that can effectively kill chemoresistant tumor cells (CRTCs) is therefore critical to overcoming these obstacles. OBJECTIVE: Here, we introduce an emerging physical feature-based therapeutic approach based on nanosecond pulsed electric fields (nsPEFs). The goal of this study is to investigate the effect of nsPEFs on CRTCs. METHODS: The cell viability, ablation effects on a 3D-cultured scaffold, and lethal thresholds of nsPEFs were evaluated according to fluorescence staining assays. RESULTS: nsPEF treatment preferentially affected chemoresistant cells (A549/CDDP) with a higher cell viability inhibition ability/cell death rate, larger ablation area, and lower ablation threshold compared to their respective homologous tumor cells (A549). The experimental and theoretical studies suggested that nsPEFs displayed selective behavior toward intracellular structures. With this selective character, nsPEFs can induce higher electroporation effects (e.g., higher pore number, larger electroporation area, and faster fluorescence dissipation on the nuclear envelope) on CRTCs due to their larger nuclear size and cell membrane capacitance. CONCLUSION: These findings demonstrated that nsPEFs induced preferential ablation of CRTCs over their respective homologous tumor cells. SIGNIFICANCE: This study provides an experimental and theoretical basis for the study of killing CRTCs by electrical treatments and suggests potential applications in the optimization of novel anti-chemoresistance methods.

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Irreversible electroporation (IRE) is a minimally invasive tumor therapy using pulsed electric field with high intensity while the important tissues such as blood vessel, bile duct, and nerve are preserved. In addition to ablation area, reversible electroporation (RE) region is also generated using needle electrodes for pulse delivery. The goal of this work is to study the generation of RE region and ablation region on a 2D lung adenocarcinoma cell model in vitro. The tumor model is exposed to electric pulses with various number. The calcium AM and propidium iodide (PI) are examined to detect the ablation area and electroporation area, respectively. The results show that electroporation area firstly tends to plateau after approximately 50 pulses, while the ablation area continues to increase. The percentage of IRE area in total electroporation area increases with additional pulses, which means that RE region could be gradually turned into ablation area with increased pulse number. However, the percentage of IRE area only achieves to 54% for 200 pulses, which indicates that RE region still cannot be completely removed. RE and IRE thresholds appear to converge as the number of pulses increases. An equation between pulse number and the electric field threshold of ablation including the electric field threshold of RE is also provided for lung adenocarcinoma cell ablation. This work may have the value for the optimization of IRE protocols on tumor ablation.

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Picosecond pulse electrical fields (psPEFs), due to their high temporal-resolution accuracy and localization, were viewed as a potential targeted and noninvasive method for neuromodulation. However, few studies have reported psPEFs regulating neuronal activity in vivo. In this paper, a preliminary study on psPEFs regulating action potentials in hippocampus CA1 of rats in vivo was carried out. By analyzing the neuronal spike firing rate in hippocampus CA1 pre- and post-psPEF stimulation, effects of frequency, duration, and dosimetry of psPEFs were studied. The psPEF used in this study had a pulse width of 500 ps and a field strength of 1 kV/mm, established by 1 kV picosecond voltage pulses. Results showed that the psPEF suppressed spike firing in hippocampal CA1 neurons. The suppression effect was found to be significant except for 10 s, 10 Hz. For short-duration stimulation (10 s), the inhibition rate of spike firing increased with frequency. At longer stimulation durations (1 and 2 min), the inhibition rate increased and decreased alternately as the frequency increased. Despite this, the inhibition rate at high frequencies (5 and 10 kHz) was significantly larger than that at 10 and 100 Hz. A cumulative effect of psPEF on spike firing inhibition was found at low frequencies (10 and 100 Hz), which was saturated when frequency reached 500 Hz or higher. This paper conducts a study on psPEF regulating spike firing in hippocampal CA1 in vivo for the first time and guides subsequent study on psPEF achieving noninvasive neuromodulation. © 2020 Bioelectromagnetics Society.

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Pulsed electric field treatment modalities typically utilize multiple pulses to permeabilize biological tissue. This electroporation process induces conductivity changes in the tissue, which are indicative of the extent of electroporation. In this study, we characterized the electroporation-induced conductivity changes using all treatment pulses instead of solely the first pulse as in conventional conductivity models. Rabbit liver tissue was employed to study the tissue conductivity changes caused by multiple, 100 µs pulses delivered through flat plate electrodes. Voltage and current data were recorded during treatment and used to calculate the tissue conductivity during the entire pulsing process. Temperature data were also recorded to quantify the contribution of Joule heating to the conductivity according to the tissue temperature coefficient. By fitting all these data to a modified Heaviside function, where the two turning points (E 0, E 1) and the increase factor (A) are the main parameters, we calculated the conductivity as a function of the electric field (E), where the parameters of the Heaviside function (A and E 0) were functions of pulse number (N). With the resulting multi-factor conductivity model, a numerical electroporation simulation can predict the electrical current for multiple pulses more accurately than existing conductivity models. Moreover, the saturating behavior caused by electroporation can be explained by the saturation trends of the increase factor A in this model. The conductivity change induced by electroporation has a significant increase at about the first 30 pulses, then tends to saturate at 0.465 S/m. The proposed conductivity model can simulate the electroporation process more accurately than the conventional conductivity model. The electric field distribution computed using this model is essential for treatment planning in biomedical applications utilizing multiple pulsed electric fields, and the method proposed here, relating the pulse number to the conductivity through the variables in the Heaviside function, may be adapted to investigate the effect of other parameters, like pulse frequency and pulse width, on electroporation.