Bioelectricity

Electrochemotherapy is an established treatment for primary and secondary cutaneous tumors of various histologies, combining chemotherapy with the delivery of high-voltage electric pulses to enhance drug uptake. Electric pulses induce water electrolysis, leading to extreme pH changes around the electrodes—acid at the anode and base at the cathode—causing tissue damage and contributing to a self-sterilizing effect, but also promoting needle corrosion. These pH shifts depend on pulse parameters, electrode geometry, and the surrounding medium; although natural tissue buffers can mitigate them, neutralization is often incomplete. This work analyzes the effect of pH changes on needle deterioration during pulse delivery.

Needle electrodes were inserted into an ex vivo tissue model and subjected to eight 100 µs monopolar pulses of 1,000 V/cm at 5,000 Hz. Every 50 trains, electrodes were inserted into a gel with a pH indicator, and a single pulse was delivered to visualize nonconducting areas. Electrode surfaces were photographed, and COMSOL simulations analyzed electric field variations due to isolated regions. Electrodes were then sanded to assess if removing corrosion restored conductivity. In addition, a buffered gel was developed to reduce corrosion.

New needles showed significant conductivity loss after 50 trains and were almost completely isolated after 150 trains. While this suffices for treating most tumors, extensive treatments requiring over 300 trains demand electrode replacement before reaching 150 trains. Sanding temporarily restores conductivity, but sanded electrodes corrode more rapidly, losing effectiveness after fewer than 50 additional trains. A specifically designed buffered gel improved electrode durability by maintaining conductivity and could help minimize skin side effects.

Electrochemotherapy (ECT) is a widely accepted treatment modality for skin cancers that are not amenable to first-line therapies. It is extensively used in both human and veterinary medicine. Various electrode designs exist, with needle tips differing by manufacturer and application. In human medicine, electrodes commonly feature conical tips, while veterinary electrodes typically have sharper, beveled tips to better penetrate the tougher skin of animals. A recurrent issue among ECT practitioners—both physicians and veterinarians—is the progressive loss of needle sharpness during treatment. This degradation increases tissue trauma, potentially delaying recovery, particularly when treating healthy surgical margins. In addition, blunted needles are prone to deflection upon insertion, which alters the inter-needle spacing. This, in turn, can compromise the uniformity of electric field distribution and leave regions of the target tissue insufficiently permeabilized.

Three needle tip geometries—conical, beveled, and triangular—were evaluated. All needles had a diameter of 7 mm. COMSOL Multiphysics® simulations were performed to assess electric field distribution for each tip type. Insertion force and the number of insertions until noticeable loss of sharpness were evaluated using an ex vivo model. In addition, the use of a guiding mask integrated into the electrode design was tested to minimize needle deflection during insertion.

COMSOL simulations showed that near the needle tip, the electric field intensity in the space between needles remained below the minimum threshold for effective tissue permeabilization, with similar patterns across all tip types. Conical tips required the highest insertion force, followed by beveled and then triangular tips. Sharpness degradation occurred most rapidly in conical needles, with significant dulling after approximately 50 insertions. Beveled tips retained functional sharpness for about 150 insertions, while triangular tips maintained it for up to 200 insertions. Triangular needles demonstrated superior insertion efficiency and durability. The inclusion of a guiding mask substantially reduced needle deflection, improving parallel alignment and maintaining electric field uniformity.

Electroporation (EP), in which pulsed electric fields permeabilize cell membranes, is widely used in biomedical and food-processing applications, including electrochemotherapy, irreversible electroporation (IRE), and gene electrotransfer (GET). Optimizing EP protocols is critical to maximize therapeutic efficacy while minimizing unintended tissue damage.

We introduce a theoretical framework for EP protocol optimization based on the spatiotemporal trajectories of ablation size, electroporation threshold, and pH-induced tissue damage. The framework analyzes how the time gradient of the electric field, derived from first principles, governs the evolution and interaction of these trajectories. The approach is evaluated using in silico and in vitro potato models and applied in vivo to GET protocols using a dorsal skinfold chamber model.

The time gradient of the electric field was found to govern all three trajectories, and their interaction determined protocol efficiency. Within the proposed framework, the entire ablation-size trajectory could be reconstructed from a single measurement obtained at the final pulse, eliminating the need to experimentally track the EP threshold trajectory. In the absence of pH effects, ablation size increased logarithmically with pulse number, while the EP threshold decayed exponentially. When pH-induced damage was included, ablation size increased logarithmically, whereas damage increased linearly. Combining these trends enabled the identification of a critical pulse number that maximizes the difference between ablation size and pH-induced damage.

This trajectory-based framework provides a unified description of EP dynamics and a first–principles–based method for optimizing pulse number across EP-based protocols. Joint consideration of ablation, threshold, and damage trajectories can guide the design of safer and more effective EP treatments.

High-intensity pulsed electromagnetic fields (HI-PEMF) can be used to trigger contactless permeabilization of the plasma membrane similar to electroporation (EP). The permeabilization efficiency and gene delivery by HI-PEMF in vitro are currently inferior to EP. It was suggested that the methodology can be improved with conductive gold nanoparticles (AuNPs), which are reported to amplify the induced electric field in close proximity to the cell membrane.

Therefore, in this work, we have studied different NPs, which varied in material/conductivity (gold and silica), size (10–50+ nm), shape (i.e., round and rods), concentration (50–200 µg/mL), and functionalization (pegylated or not), and combined them with HI-PEMF (6.7 T × 100 pulses, 1 Hz).

The normal Chinese hamster ovary cell line (CHO) and the cancer human urinary bladder’s transitional carcinoma cell line (T24) were used as a model. We have characterized cell membrane permeabilization using propidium iodide (PI) and the efficacy of gene delivery using pEGFP-N1.

Larger NPs and higher NP concentrations resulted in up to a 10% increase in membrane permeability. In contrast, semispherical and rod-shaped AuNPs did not further enhance permeabilization efficiency. Gene delivery efficiency increased from 3% in control samples to 6% in the presence of 50 nm AuNPs. Overall, CHO cells were more susceptible to HI-PEMF-induced effects than T24 cells.

This study shows the potential to increase gene delivery efficacy by combining HI-PEMF treatment with conductive NPs. However, it was concluded that the HI-PEMF-induced effects are highly dependent on the cell line, NP type, and concentration and therefore require further investigation.

Electroporation ablation is a promising nonsurgical and minimally invasive technique for tumor ablation; however, no monitoring is currently available. In this article, we present recent advances in the numerical workflow toward a peroperative numerical evaluation of clinical irreversible electroporation (IRE) procedures of liver tumors. The objective of this study is to propose an updated numerical workflow for the digital twin of electroporation ablation, to provide relevant information to physicians performing IRE for hepatocellular carcinoma (HCC).

The workflow consists of four main steps: (1) an image registration algorithm to align the contrast-enhanced cone beam computed tomography (CBCT), where the region of interest are visible, with the lower-quality CBCT acquired after needle insertion; (2) extraction of needles position by manual selection directly on the CBCT containing the needles; (3) accurate and efficient numerical computation of the electric field (EF) distribution, using a static linear model and the finite difference method to simulate the EF at the maximum voltage applied between each electrode pair; and (4) numerical assessment of the tumor coverage by the 3D EF.

We propose a criterion for electrical heterogeneity of the medium near the electrode thanks to the measurements provided by the Nanoknife IRE device. The full protocol was tested on three representative patients with nodular HCCs <5 cm. The complete numerical workflow, from image registration and needle detection to the computation, requires at most less than 15 min following image acquisitions, making it suitable for clinical use. Interestingly, the number of finite difference computations increases linearly with the number of needles N, despite the number of electrode pairs increasing as N ( N − 1 ) / 2 . In addition, the pulse amplitude can be modified without the need for full recomputation, enabling online adjustment of the treatment plan.

Pulsed electric field (PEF) technology shows promise for microbial control in biorefinery applications. However, its effectiveness in mixed cultures remains poorly understood. This study investigated the differential effects of PEF treatment on bacterial inactivation and algal protein preservation in a coculture of Chlorella vulgaris algae and Delftia sp. bacteria.

Algal and bacterial viable cell counts and viability were quantified using flow cytometry with differential fluorescent staining (SYTO 9, YO-PRO-1, fluorescein diacetate [FDA]), bacterial growth was monitored spectrophotometrically at 600 nm, protein extraction was determined by modified Lowry assay, protein profiles analyzed by SDS-PAGE, and extract antimicrobial activity was assessed by agar diffusion and growth inhibition assays. We compared PEF treatments at two energy levels (4 and 100 J/mL) against high-pressure homogenization (HPH) as a control, with assessments at different growth phases (days 1, 3, and 7).

While PEF consistently inactivated >95% of algal cells, regardless of the growth phase, bacterial inactivation varied significantly, with maximum susceptibility on day 3 (70–80% mortality) when bacteria entered the starvation phase. Unexpectedly, on day 7, PEF treatment of cocultures led to bacterial proliferation, with viable counts increasing up to 4-fold compared with untreated controls. Analysis of algal extracts showed no antimicrobial activity against bacteria, and instead supported bacterial proliferation, suggesting that cellular disruption releases compounds that can be metabolized by surviving bacteria. Furthermore, while PEF preserved the integrity of algal protein profiles regardless of bacterial presence, HPH treatment of cocultures introduced a novel ∼27 kDa protein band, suggesting bacterial contamination of the extract.

These findings reveal the complex, growth phase-dependent dynamics inherent in PEF treatment of mixed microbial systems and provide critical insights into biorefinery applications in which microbiological control and product quality must be balanced.