Characterization of glioma spheroid viability and metastatic potential following monophasic and biphasic pulsed electric fields.

in Bioelectrochemistry (Amsterdam, Netherlands) by Julio P Arroyo, Edward J Jacobs, Raffae N Ahmad, Ashil J Amin, Scott S Verbridge, Rafael V Davalos

TLDR

  • A glioblastoma multicellular tumor spheroid (MTS) was integrated with a collagen hydrogel to study the effects of pulsed electric fields (PEFs) on viability, proliferation, and migration. Results showed that MTS exposed to longer pulse widths and higher electric fields experienced ablation, while smaller pulse widths and lower electric fields led to partial ablation and recuperation.

Abstract

Currently, the leading 3D cell culture models for characterizing and validating pulsed electric fields (PEFs) are spheroids and cell-laden hydrogels. We hypothesize that incorporating a glioblastoma multicellular tumor spheroid (MTS) onto a collagen hydrogel will leverage their strengths to form a more physiologically relevant model to study viability, proliferation, and migration. The MTS-hydrogel platform was subjected to PEFs varying in pulse width and electric field (EF) strength. Treated MTS were monitored and evaluated for viability and proliferation (Live/Dead imaging, XTT Cell Viability Assay), and migration (brightfield imaging) over 5 days post-treatment. In vitro experimentation was validated with a multi-layered spheroid finite element model, evaluating transmembrane potential (TMP), pore density, and pore formation across the spheroid layers. MTS exposed to longer pulse widths (5, 100 μs) and higher EFs (2000, 2500 V/cm) experienced a complete ablation. Smaller pulse widths and lower EFs produced partial ablations initially reducing the MTS, but unable to prevent the MTS from recuperating. Similarly shown with the computational model, a TMP was accomplished through the MTS, inducing electroporation; however, pore formation was dictated by the increase in pulse width and EF beyond the superficial layer. EFs of 2000 V/cm and above severely constrained the migration independent of pulse width.

Overview

  • The study aimed to create a more physiologically relevant model for characterizing and validating pulsed electric fields (PEFs) using a glioblastoma multicellular tumor spheroid (MTS) incorporated onto a collagen hydrogel.
  • The model was subjected to PEFs with varying pulse widths and electric field (EF) strengths, and monitored for viability, proliferation, and migration over 5 days post-treatment.
  • The study linked pulsed electric field treatment to changes in transmembrane potential, pore density, and pore formation across the spheroid layers, and explored its effects on migration independent of pulse width.

Comparative Analysis & Findings

  • MTS exposed to longer pulse widths (5, 100 μs) and higher EFs (2000, 2500 V/cm) experienced complete ablation.
  • Smaller pulse widths and lower EFs produced partial ablations initially reducing the MTS, but unable to prevent the MTS from recuperating.
  • EFs of 2000 V/cm and above severely constrained migration independent of pulse width.

Implications and Future Directions

  • The study demonstrates the potential of combining MTS-hydrogel platforms with computational modeling to better understand the effects of PEFs on tumor viability, proliferation, and migration.
  • Future studies could explore the use of varying composition and structure of collagen hydrogels to further enhance the in vitro model, and investigate the effects of PEFs on specific cell populations within the MTS.
  • The findings also highlight the need for further research on the optimal PEF settings to achieve the desired level of ablation while minimizing systemic effects, and to explore potential applications in non-oncological fields such as biofilm control and wound healing.
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