(416i) Enhanced Gene Delivery by Transverse Cell Migration During Flow-through Electroporation

Permeabilization of cell membrane is an essential step for transfer of foreign genes into cells. Electroporation permeabilizes cell membrane by generating nanoscale pores using an external electric field. In common electroporation practice, short pulses are applied to cells that are static in the suspension. Because transmembrane potential varies on the cell surface depending on the alignment between the membrane normal and the field direction, only limited area of the cell surface is permeabilized during these procedures and this hinders the improvement on the delivery efficiency. In this report, we study how cell migration under hydrodynamic forces in a microfluidic channel affects electroporation and gene delivery during a flow-through electroporation process. During flow-through electroporation, high electroporation field is confined to a specific section of the channel with small cross-sectional area when a constant voltage is applied cross the channel and cells flow through the channel with a constant velocity. We tested devices with straight and spiral electroporation sections. In a device with a straight electroporation section, flowing cells are focused into equilibrium positions. Electropermeabilization and DNA delivery are limited to partial surface area ranging from one pole of the cell to a circular stripe at the cell equator, depending on the duration in the electroporation section. On the other hand, when flow-through electroporation is conducted in a spiral electroporation section, we observe transverse migration of cells in the channel when they are entrained in the Dean flow. DNA delivery in this case occurs to the entire surface of cells. We also examine the amount of DNA delivered in different channels and the gene expression after delivery. The device with spiral electroporation section yields superior performance in both cases with the same flow and electric conditions. The differences in these DNA delivery results are explained by the combined influence from transverse cell migration under Dean flow and cell spinning in a shear field. These findings suggest a new approach to enhance gene delivery during electroporation by manipulating cell migration in the flow.