Microneedle arrays for intracellular recording applications

This paper reports on the fabrication and application of microneedles for the electroporation of adherently growing cells and intracellular recording with focus on the influence on external factors on the cell behavior. Patch-on-chip methods such as patch-clamp have been applied mostly to individual cells in suspension. However, in the human body most of cells are adherently growing cells, which motivated the development of a new chip design. The chip contains an array of 64 microneedles occupying a total area of approximately 1 mm(2). The microneedles are fabricated using dry etching of silicon, followed by an insulation, metallization and passivation. The passivation layer is opened at the tip of the needles in order to expose the metal for cell positioning via dielectrophoresis, cell electroporation, as well as intracellular recording. Various needles with diameters in the sub-micron range and heights below 10 mu m have been fabricated. Heart muscle cells, fibroblasts, and primary neuronal cells of mice were grown on these microneedle arrays. To electrically access the intracellular space, the cells were electroporated with a voltage of 2 V. Preliminary tests show that more than 80% of the cells could successfully be porated.