High-Throughput Single-Cell Electroporation Using Geometrically Induced Pulses

Authors: 
Figueroa-Espada, C. G., University of Puerto Rico, Mayagüez
Dávila-Andino, M. E., University of Puerto Rico, Mayagüez
Díaz-Rivera, R. E., University of Puerto Rico, Mayagüez
Single-cell electroporation is a technique that consists of applying a strong pulsed electric field (PEF) to single cells in order to create a transient permeabilization in the cell’s plasma membrane. While this technique could be used more easily for the transport of molecules into cells for a wide range of applications such as CRISPR Cas9 genome editing, it is largely empirical which translates to being difficult to control. It also shows low transfection yields in batch treatment and low cell viability, thereby limiting biomedical applications. Here, we propose a PDMS microfluidic device in which flow-through electroporation can be reliably performed for large volumes of cells. This device was fabricated via soft lithography and it is composed of a straight channel with multiple heights and width reductions in series called “pinch” zones. A low constant voltage is applied across the microfluidic channel, where the cells are moving with the laminar flow. The dimensions of the straight channel are such that the cells do not experience electropermeabilization. However, cells must mechanically deform in the pinch zone in order to flow through. Which in turn, induces a local high-intensity field with a pulse duration which is equal to the cell’s transit time through the pinch zone. By flowing a single cell in multiple pinch zones in series, we can simulate a train of PEF, typically used in electroporation protocols. By measuring the current through the system as a function of time, we were able to quantify current drops as the cell passes through the multiple pinch zones. Preliminary results suggest electroporation happens when 6 V are applied across the entire device and that the process can be monitored in real time. Based on a simple analytical model derived from the volume resistivity equation and the experimental data, we estimated that the voltage drop across the whole cell varies from 350 to 950 mV depending on the pinch zone number.