CMOS microcavity arrays for single-cell electroporation and lysis

Abstract

Transfection is a key function for many single-cell analyses. Reversible electroporation (EP) using high intensity electric fields is a simple means of transfection applicable to most cell types. For reversible EP, precise control over the electric field is critical to regulate the induced pore densities in the membrane and maintain cell viability. Individually accessible microelectrode arrays enabled by semiconductor fabrication methods have emerged as a viable technology for single-cell analyses but do not provide for effective electroporation capabilities due to the planar arrangement of electrodes. Towards the goal of a fully integrated single-cell analysis platform, we utilize a commercial complementary metal-oxide-semiconductor (CMOS) process to realize microcavities which allow for single-cell confinement with integrated three-dimensionally aligned electrodes for effective poration. The structure is formed using the inherent metal stack available within the CMOS process as a hard etch mask for deep-reactive ion etching. Using this structure, to our knowledge, we present the first on-CMOS demonstration of controlled electroporation with the goal of transfection using human embryonic kidney cells (HEK-293) stained with Calcein as a model. We report an increase in calcein leaching from the cells subject to increasing electric field intensities with subsequent reuptake confirming cell viability post electroporation. These results are supported by numerical simulation of theoretical pore density which are in good agreement with numerical simulation. Combined with simple optical or electrical feedback, the structure is suitable for precise electroporation control in single-cells.

Keywords: CMOS microelectrode array; Electroporation; Lab on CMOS; Lab on a chip; Transfection; single cell analysis.