Single cell electroporation using microfluidic devices.

Electroporation is a powerful technique to increase the permeability of cell membranes and subsequently introduce foreign materials into cells. Pores are created in the cell membrane upon application of an electric field (kV/cm). Most applications employ bulk electroporation, at the scale of 1 mL of cells (ca. one million cells). However, recent progresses have shown the interest to miniaturize the technique to a single cell. Single cell electroporation is achieved either using microelectrodes which are placed in close vicinity to one cell, or in a microfluidic format. We focus here on this second approach, where individual cells are trapped in micrometer-size structures within a microchip, exposed in situ to a high electric field and loaded with either a dye (proof-of-principle experiments) or a plasmid. Specifically, we present one device that includes an array of independent electroporation sites for customized and successive poration of nine cells. The different steps of the single cell electroporation protocol are detailed including cell sample preparation, cell trapping, actual cell poration and on-chip detection of pore formation. Electroporation is illustrated here with the transport of dyes through the plasma membrane, the transfection of cells with GFP-encoding plasmids, and the study of the ERK1 signaling pathway using a GFP-ERK1 protein construct expressed by the cells after their transfection with the corresponding plasmid. This last example highlights the power of microfluidics with the implementation of various steps of a process (cell poration, culture, imaging) performed at the single cell level, on a single device.