Microdosimetric calibration of microsecond pulsed electric field stimulation across electrodes technologies for the RISEUP project

RISEUP, short for Regeneration of Injured Spinal Cord by Electro Pulsed Bio-Hybrid Implant, is a European project aimed at offering a real possibility of recovery after spinal cord injury. This approach leverages highly intense microsecond pulsed electric fields (& micro;sPEFs) to transiently permeabilize cellular membranes, thereby guiding stem cells proliferation and differentiation pathways. In vitro experiments are underway to develop an optimized stimulation protocol. An initial experimental phase employed faced electrodes (FE), while a second phase uses cylindrical electrodes (CE), corresponding to electro pulsed bio-hybrid (EPB) device - Prototype 0. Since the two configurations generate different electric (E-) field distributions, a numerical calibration of the voltage applied to the CE system was required. The objective of this calibration is to ensure that the E-field intensities generated between the CE electrodes match those previously shown to induce electroporation responses in stem cells with the FE setup. Numerical models of both FE and CE were implemented in COMSOL Multiphysics, and a calibration procedure was fine-tuned to ensure that the CE setup produced an average electric field comparable to the 30 kV/m value achieved by the FE system. The calibration process adjusted the applied voltage in the CE system from the nominal 15 V to 35.4 V to achieve a median electric field of 30 kV/m within the extracellular matrix volume that will host the stem cells. Following this, a microdosimetric study using advanced 3D virtual stem cells, including intracellular compartments, was performed to validate the calibration. The study confirmed that the two systems produced comparable electroporation effects, as evidenced by similar transmembrane potentials and pore densities on both plasma and intracellular membranes. The developed calibration methodology effectively harmonizes the stimulation conditions between different electrodes technologies employed in the RISEUP project, providing crucial support for optimizing in vitro protocols during experimental phases.