Picosecond Pulse Electrical Field Suppressing Spike Firing in Hippocampal CA1 in Rat In Vivo.

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.

Ablation outcome of irreversible electroporation on potato monitored by impedance spectrum under multi-electrode system.

BACKGROUND: Irreversible electroporation (IRE) therapy relies on pulsed electric fields to non-thermally ablate cancerous tissue. Methods for evaluating IRE ablation in situ are critical to assessing treatment outcome. Analyzing changes in tissue impedance caused by electroporation has been proposed as a method for quantifying IRE ablation. In this paper, we assess the hypothesis that irreversible electroporation ablation outcome can be monitored using the impedance change measured by the electrode pairs not in use, getting more information about the ablation size in different directions. METHODS: Using a square four-electrode configuration, the two diagonal electrodes were used to electroporate potato tissue. Next, the impedance changes, before and after treatment, were measured from different electrode pairs and the impedance information was extracted by fitting the data to an equivalent circuit model. Finally, we correlated the change of impedance from various electrode pairs to the ablation geometry through the use of fitted functions; then these functions were used to predict the ablation size and compared to the numerical simulation results. RESULTS: The change in impedance from the electrodes used to apply pulses is larger and has higher deviation than the other electrode pairs. The ablation size and the change in resistance in the circuit model correlate with various linear functions. The coefficients of determination for the three functions are 0.8121, 0.8188 and 0.8691, respectively, showing satisfactory agreement. The functions can well predict the ablation size under different pulse numbers, and in some directions it did even better than the numerical simulation method, which used different electric field thresholds for different pulse numbers. CONCLUSIONS: The relative change in tissue impedance measured from the non-energized electrodes can be used to assess ablation size during treatment with IRE according to linear functions.

Efficacy and mechanism of steep pulse irreversible electroporation technology on xenograft model of nude mice: a preclinical study.

BACKGROUND: Steep pulse therapy can irreversible electrically brackdown of tumor membrance and cause cell death. In previous studies, we investigated the effect of steep pulsed electroporation on the killing of large cell lung cancer cell line L981- in vitro, and determined the best parameters for killing lung cancer cells by steep pulse technology. But the optimal parameters and the mechanisms of steep pulse irreversible electroporation technology on nude mouse tumor model are unclear. METHODS: Three settings of steep pulse therapy parameters were applied to the nude mouse model. An in vivo imaging system was employed to observe the effect of different parameters on the mouse model. The pathological changes of the tumor tissue and immunofluorescence data on Caspase-3 protein expression were recorded. RESULTS: Under the in vivo imaging system, the steep pulse had an obvious inhibitory effect on the transplanted tumor in the nude mouse model. Pathological tests showed that occurrence of necrosis and apoptosis and expression of Caspase-3 protein in the tumor tissue were increased compared to those in the normal tissue. CONCLUSIONS: Steep pulse irreversible electroporation technology showed a promising antitumor effect in the nude mouse tumor model. With splint-type electrode, the best treatment parameters determined for the nude mouse tumor model were voltage amplitude 2000 V/cm, pulse width 100 µs, pulse frequency 1 Hz, pulse number 60, and repeat time 3. Moreover, steep pulse induced coagulative necrosis of tumor tissue by cell apoptosis.

The effects of a picosecond pulsed electric field on angiogenesis in the cervical cancer xenograft models.

OBJECTIVE: The application of picosecond pulsed electric field (psPEF) is a new biomedical engineering technique used in cancer therapy. However, its effects on cervical cancer angiogenesis are not clear. Therefore, the aim of the present study is to investigate the effects of psPEF on angiogenesis in cervical cancer xenograft models. METHODS: Xenograft tumors were created by subcutaneously inoculating nude mice (athymic BALB/c nu/nu mice) with HeLa cells, then were placed closely between tweezer-type plate electrodes and subjected to psPEF with a gradually increased electric field intensity (0kV/cm, 50kV/cm, 60kV/cm, 70kV/cm). The direct effect on tumor tissue was observed by hematoxylin and eosin (H&E) staining and transmission electron microscopy (TEM). The changes of blood vessels and oxygen saturation (sO2) of tumors were monitored in vivo by photoacoustic tomography (PAT). The microvessel density (MVD), vascular endothelial growth factor (VEGF) and hypoxia-inducible transcription factors (HIF-1α and HIF-2α) were detected by immunohistochemical technique (IHC). Their protein expressions and gene transcription levels were evaluated using western blot (WB) and quantitative reverse transcription and polymerase chain reaction (RT-PCR). RESULTS: PsPEF induced obvious necrosis of cervical cancer tissue; with the increasing of electric field intensity, the MVD, vascular PA signal and sO2 values declined significantly. The protein expression and gene transcription levels of VEGF, HIF1α and HIF2α were significantly decreased at the same time. CONCLUSION: PsPEF exhibited dramatic anti-tumor and anti-angiogenesis effects in cervical cancer xenograft models by exerting direct effect on cancer cells and vascular endothelial cells and indirect effect on tumor angiogenesis-related factors.

Simulation study of delivery of subnanosecond pulses to biological tissues with an impulse radiating antenna.

We have numerically studied the delivery of subnanosecond pulsed radiation to biological tissues for bioelectric applications. The antenna fed by 200 ps pulses uses an elliptical reflector in conjunction with a dielectric lens. Two numerical targets were studied: one was a hemispherical tissue with a resistivity of 0.3-1 S/m and a relative permittivity of 9-70 and the other was a realistic human head model (HUGO). The electromagnetic simulation shows that despite tissue heterogeneity of the human head, the electric field converges to a spot 8 cm in depth and the spot volume is approximately 1 cm × 2 cm × 1 cm in both cases when using only the reflector and a lens as an addition. Rather than increasing as it approaches the converging point, the electric field decreases strongly with distance from the skin to the converging point due to tissue resistive loss. The electric field distribution, however, can be reversed by making the dielectric lens lossy with the two innermost layers being partially resistive. The lossy lens causes an attenuation of the electric field near the axis, but the electric field generated by the waves which pass the lens at a wider angles compensate for this loss. A local maximum electric field in a deeper region of the tissue may form with the lossy lens. The study shows that it is possible to generate the desired electric field distribution in the complex biological target by modifying the dielectric properties of the lens used in conjunction with the reflector antenna.

Dynamics of Cell Death Due to Electroporation Using Different Pulse Parameters as Revealed by Different Viability Assays.

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.

The Enhancement of Tumor Ablation Effect by the Combination of High-Frequency and Low-Voltage Bipolar Electroporation Pulses.

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.

An experimental and theoretical study on cell swelling for osmotic imbalance induced by electroporation.

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.

A Big Prospect for Hydrogel Nano-System in Glioma.

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.

Optimal Irreversible Electroporation Combined with Nano-Enabled Immunomodulatory to Boost Systemic Antitumor Immunity.

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.

Synergistic Bipolar Irreversible Electroporation for Tumor Ablation without Muscle Contraction.

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.

Irreversible electroporation and apoptosis in human liver cancer cells induced by nanosecond electric pulses.

The goal of this study was to assess the effect of nanosecond electric pulses on HepG2 human liver cancer cells. Electric pulses with a high strength of 10 kV/cm, duration of 500 ns and frequency of 1 Hz were applied to the cells. After delivery of electric pulses, apoptosis, intracellular calcium ion concentrations, transmembrane mitochondrial potentials, electropermeabilization and recovery from electropermeabilization in cells were investigated. The results showed that electric pulse treatment for 20 s and more could trigger apoptosis in cells. Real-time observation indicated an immediate increase in intracellular calcium ion concentration and a dramatic decrease in mitochondrial membrane potential in cells responding to electric pulses. In subsequent experiments, propidium iodide uptake in cells emerged after exposure to electric pulses, indicating electropermeabilization of the cell membrane. Furthermore, recovery from electropermeabilization was not observed even 4 h after the stimulation, demonstrating that irreversible electropermeabilization was induced by electric pulses. In conclusion, electric pulses with a high strength and nanosecond duration can damage cancer cells, accompanied by a series of intracellular changes, providing strong evidence for the application of electric pulses in cancer treatment.

Study on the application of an ultra-high-frequency fractal antenna to partial discharge detection in switchgears.

The ultra-high-frequency (UHF) method is used to analyze the insulation condition of electric equipment by detecting the UHF electromagnetic (EM) waves excited by partial discharge (PD). As part of the UHF detection system, the UHF sensor determines the detection system performance in signal extraction and recognition. In this paper, a UHF antenna sensor with the fractal structure for PD detection in switchgears was designed by means of modeling, simulation and optimization. This sensor, with a flat-plate structure, had two resonance frequencies of 583 MHz and 732 MHz. In the laboratory, four kinds of insulation defect models were positioned in the testing switchgear for typical PD tests. The results show that the sensor could reproduce the electromagnetic waves well. Furthermore, to optimize the installation position of the inner sensor for achieving best detection performance, the precise simulation model of switchgear was developed to study the propagation characteristics of UHF signals in switchgear by finite-difference time-domain (FDTD) method. According to the results of simulation and verification test, the sensor should be positioned at the right side of bottom plate in the front cabinet. This research established the foundation for the further study on the application of UHF technique in switchgear PD online detection.

[The anti-tumor efficacy of nanosecond pulsed electric fields on the mouse with melanoma xenograft in vivo].

This study was conducted to investigate the anti-tumor efficacy of nanosecond pulsed electric fields (nsPEFs) on the mouse with A375-GFP melanoma xenograft in vivo. In vivo fluorescence image analysis system was used in this study to evaluate the effects of nsPEFs on human melanoma A375 cell xenograft. On the Day 90 af ter pulse delivery, the skin that had contained A375 cell xenograft was surgically excised and pathologically evalua ted. The changes of scar were recorded by digital camera. The experiment revealed that significant changes in fluorescence value trend and amplitude were found in the treated group from those in the control group. The fluorescence of tumor in the treated group decreased mostly 48 h after the treatment and completely disappeared 10 d after the treatment, while that in control group was increased gradually. Surgical excision of the area confirmed a complete pathologic response. Within a few days after the nsPEFs treatment, a hard scab formed at the treatment region. The scab fell off by the end of the second week. As time went on, the scar gradually became faded and all xenograft tumors were disappeared without recurrence. From the experiment, we learn that nsPEFs can bring good therapeutic effect. It may provide a new approach for the clinical treatment of superficial tumors.

Study on B16 Cell Cytotoxicity by High Frequency Reversible Electroporation With Bleomycin That Induces Hallmarks of Immunogenic Death.

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.

Superior Surface-Insulated Polymers with Low Leakage Current Enabled by Tailored Coatings Deposited with Colliding Plasma Jets.

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.

Scheduled dosage regimen by irreversible electroporation of loaded erythrocytes for cancer treatment.

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.

[Induction of apoptosis of ovarian cancer cells and influence on Fas-mediated apoptosis pathway by nanosecond pulsed electric fields].

This paper is to investigate the apoptosis effect of ovarian cancer SKOV3 cells induced by nanosecond plused electric fileds (nsPEFs) and to study its influence on Fas-mediated apoptosis. SKOV3 cell were exposed to the 45kV/cm of field intensity, 30 pulses, and 50ns, 100ns, and 200ns of pulse width, respectively. Flow cytometry were used to assay apoptosis. Agarose gel electrophoresis was used to detect DNA ladder. Real time PCR (RT-PCR) and Western blot analysis were used to measure the expression level of Fas, FasL, caspase-8 and Bid. Flow cytometry results revealed that the late apoptosis rates and (or) necrosis were significantly higher than those in control group (3.03% +/- 0.57%) (P < 0.05), with apoptosis rates and (or) necrosis being (18.31 +/- 0.65%), (45.55% +/- 3.71%), (47.47% +/- 7.01%) in the groups of 50ns, 100ns, 200ns, respectively. A typical DNA ladder pattern of internucleosomal fragmentation was observed in the groups of 50ns and 100ns, but not clear in the 200ns group. RT-PCR results revealed that the mRNA expression of Fas, FasL, caspase8 and Bid were significantly increased in groups of 50ns, 100ns, but significantly decreased in group of 200ns (P < 0.05). Meanwhile, Western blot analysis demonstrated that the Fas, FasL, Caspase-8 and Bid expression were significantly higher in groups of 50ns, 100ns, but significantly lower in group of 200ns (P < 0.05). It indicated that 45kV/cm, 50ns, 100ns nsPEFs could induce apoptosis in ovarian cancer SKOV3 cells and activate Fas-mediated apoptosis pathway.

The Enlargement of Ablation Area by Electrolytic Irreversible Electroporation (E-IRE) Using Pulsed Field with Bias DC Field.

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.