Bioimpedance Analysis of Epithelial Monolayers after Exposure to Nanosecond Pulsed Electric Fields

Uncertainty Quantification and Sensitivity Analysis for the Electrical Impedance Spectroscopy of Changes to Intercellular Junctions Induced by Cold Atmospheric Plasma

The influence of pertinent parameters of a Cole-Cole model in the impedimetric assessment of cell-monolayers was investigated with respect to the significance of their individual contribution. The analysis enables conclusions on characteristics, such as intercellular junctions. Especially cold atmospheric plasma (CAP) has been proven to influence intercellular junctions which may become a key factor in CAP-related biological effects. Therefore, the response of rat liver epithelial cells (WB-F344) and their malignant counterpart (WB-ras) was studied by electrical impedance spectroscopy (EIS). Cell monolayers before and after CAP treatment were analyzed. An uncertainty quantification (UQ) of Cole parameters revealed the frequency cut-off point between low and high frequency resistances. A sensitivity analysis (SA) showed that the Cole parameters, R₀ and α were the most sensitive, while R_inf and τ were the least sensitive. The temporal development of major Cole parameters indicates that CAP induced reversible changes in intercellular junctions, but not significant changes in membrane permeability. Sustained changes of τ suggested that long-lived ROS, such as H₂O₂, might play an important role. The proposed analysis confirms that an inherent advantage of EIS is the real time observation for CAP-induced changes on intercellular junctions, with a label-free and in situ method manner.

Ultralong recovery time in nanosecond electroporation systems enabled by orientational-disordering processes

The growing importance of applications based on molecular medicine and genetic engineering is driving the need to develop high-performance electroporation technologies. The electroporation phenomenon involves disruption of the cell for increasing membrane permeability. Although there is a multitude of research focused on exploring new electroporation techniques, the engineering of programming schemes suitable for these electroporation methods remains a challenge. Nanosecond stimulations could be promising candidates for these techniques owing to their ability to generate a wide range of biological responses. Here we control the membrane permeabilization of cancer cells using different numbers of electric-field pulses through orientational disordering effects. We then report our exploration of a few-volt nanosecond alternating-current (AC) stimulation method with an increased number of pulses for developing electroporation systems. A recovery time of ∼720 min was achieved, which is above the average of ∼76 min for existing electroporation methods using medium cell populations, as well as a previously unreported increased conductance with an increase in the number of pulses using weak bias amplitudes. All-atom molecular dynamics (MD) simulations reveal the orientation-disordering-facilitated increase in the degree of permeabilization. These findings highlight the potential of few-volt nanosecond AC-stimulation with an increased number of pulse strategies for the development of next-generation low-power electroporation systems.

Electroporation Microchip with Integrated Conducting Polymer Electrode Array for Highly Sensitive Impedance Measurement

OBJECTIVE

Monitoring of impedance changes during electroporation-based treatments can be used to study the biological response and provide feedback regarding treatment progression. However, seamless integration of the sensing electrodes with the setup can be challenging and high impedance sensing electrodes limit the recording sensitivity as well as the spatial resolution. Here, we present an all-in-one microchip containing stimulation electrodes, as well as an array of low impedance, micro-scale sensing electrodes for highly sensitive electrical impedance spectroscopy.

METHODS

An in vitro platform is fabricated with integrated stimulation and sensing electrodes. To reduce the impedance, the sensing electrodes are coated with the conducting polymer PEDOT:PSS. The performance is studied during the growth of a confluent cell layer and treatment with electrical pulses.

RESULTS

Coated electrodes, compared to uncoated electrodes, show more pronounced impedance changes in a broader frequency range throughout the formation of a confluent cell layer and electrical treatment.

CONCLUSION

PEDOT:PSS coatings enhance monitoring of impedance changes with micro-scale electrodes, enabling high spatial resolution and increased sensitivity.

SIGNIFICANCE

Enhanced monitoring techniques can be utilized to study electroporation dynamics and monitor treatment progression for better understanding of underlying mechanisms and improved outcomes.

Recent progress in pulsed electric field ablation for liver cancer

The number of liver cancer patients is likely to continue to increase in the coming decades due to the aging of the population and changing risk factors. Traditional treatments cannot meet the needs of all patients. New treatment methods evolved from pulsed electric field ablation are expected to lead to breakthroughs in the treatment of liver cancer. This paper reviews the safety and efficacy of irreversible electroporation in clinical studies, the methods to detect and evaluate its ablation effect, the improvements in equipment and its antitumor effect, and animal and clinical trials on electrochemotherapy. We also summarize studies on the most novel nanosecond pulsed electric field ablation techniques in vitro and in vivo. These research results are certain to promote the progress of pulsed electric field in the treatment of liver cancer.