A Device to Ensure In Vitro Controlled and Sustained Cells Exposure to Electrical Stimulations: The Example of Calcium Oscillations Control in Mesenchymal Stem Cells with Microsecond Pulsed Electric Fields

Cell stimulation with electric fields (EFs) can be used for a variety of purposes. Among the different types of EFs, pulsed EFs (PEFs) have been extensively employed to induce cell membrane electropermeabilization. This approach can be used as a vectorization method to introduce inside cells compounds whose dimensions may range from the size of an ion to the size of a large nucleic acid. Thus, there is a wide scope of applications for electropermeabilization. For example, the use of PEFs of microseconds duration (µsPEFs) has been shown to be a convenient tool to modulate calcium (Ca 2+ ) oscillations in mesenchymal stem cells (MSCs) by generating a limited and controlled electropermeabilization to external Ca 2+ ions. These data highlight the interest in developing methodologies suitable for long-term electric stimulations. We describe here a device that allows the delivery of µsPEFs to attached cells, in a classical Petri dish, in a long-term manner, while ensuring the maintenance of sterility. This device is simple, easy to elaborate at a low cost, and it allows to perform multiple experiments in parallel, as well as microscopy recordings during (and/or after) the delivery of µsPEFs to cells, a very convenient approach to directly assess the effects of the electrical stimulations. The conception of the system prevents medium leaks by capillarity, which allows avoiding losses of the medium and its potential contamination. We also analyzed the geometry of the electrodes and demonstrated the superiority of the plate electrodes compared with wires when the most homogeneous field distribution on the cell layer is sought. The choice of the material constituting the electrodes, in terms of cost and limited electrochemical reactions, is also discussed. The interest of this cost-effective device is documented with an example dealing with the control of Ca 2+ cytosolic oscillations in MSCs.