## 1 Introduction
The tumor treatment method utilizing pulsed electric fields mainly applies electric fields to the local lesion area through electrodes, disrupting the insulation properties of local tissue cell membranes, inducing the formation of micro-pores or electric pores, increasing membrane permeability and conductivity, disrupting the physiological balance inside and outside the cell, and ultimately leading to cell death [12]. High-intensity pulsed electric fields with microsecond durations (1-100 \(\upmu\)s) can cause the irreversible perforation of cell membranes, leading to the collapse of transmembrane potential, disruption of cell membrane integrity, and release of intracellular contents, ultimately resulting in tumor cell death. This therapy is highly controllable, non-toxic, efficient, and has shown promising clinical efficacy [13]. However, the prolonged duration of pulse application can lead to strong muscle contractions in patients, which can be inconvenient during treatment. Consequently, sub-microsecond pulse electric fields (200-500 ns) have garnered increased attention, as their shorter pulse width acts simultaneously on intracellular and extracellular membranes, exploiting their potential to induce markedly different biological effects due to their pulse width being shorter than the cell membrane's charging time [14]. This approach exhibits low side effects and high safety, showing excellent prospects for application. Researchers have conducted simulation studies on the perforation characteristics under the influence of pulse electric fields using molecular dynamics [15], finite element models [16], numerical models [17], and equivalent circuit models [18]. Moreover, experimental studies using techniques such as fluorescence probes [19], microscopy [20], and impedance measurement [21] have been carried out to analyze DNA damage [22], morphological changes [23], and changes in dielectric properties [24] induced by nanosecond pulses. These studies aim to elucidate the interaction mechanisms between electric fields and cells/tissues and preliminarily verify the safety and effectiveness of pulse electric fields in clinical tumor treatment, thereby promoting rapid development in the biomedical field. Further research has revealed that high-voltage nanosecond pulsed electric fields (nsPEFs) with pulse widths shortened to several nanoseconds have rich high-frequency components, which can selectively disrupt and perforate organelles without compromising the surface membrane integrity [25; 26]. nsPEFs can also dissipate mitochondrial membrane potential [27], induce intracellular calcium waves [28], and damage chromosome telomeres [29]. Additionally, nsPEFs exert mechanical effects on subcellular structures in tumor cells, particularly affecting actin, microtubules, and intermediate filaments in the cell skeleton [30; 31]. However, the mechanism of the force-electric response of nsPEFs on tumor cells remains unclear and necessitates further exploratory research in this field. Therefore, this study aims to investigate the biophysical and electrical effects of nsPEFs on tumor cells through a combination of theoretical and experimental approaches. Firstly, a multiphysical field model is developed to simulate and analyze the electrical perforation and Maxwell stress experienced by cell membranes and nuclear membranes under nsPEFs in the presence of high-frequency electric fields. Secondly, to assess the impact of nsPEFs on subcellular structures, preliminary investigations are conducted on the bioelectrical responses of cell skeletons and subcellular structures using human breast cancer cells (MDA-MB-231) in cell experiments. Thirdly, the dose-effect relationship between nsPEFs and the bioelectrical responses of subcellular structures such as endoplasmic reticulum, mitochondria, and the cell nucleus is examined. The findings from this study hold significant scientific and medical value, providing important insights for the research and application of high-voltage nsPEFs in the field of biomedical engineering.