Micromotor-based localized electroporation and gene transfection of mammalian cells

Herein, we studied localized electroporation and gene transfection of mammalian cells using a metallodielectric hybrid micromotor that is magnetically and electrically powered. Much like nanochannel-based, local electroporation of single cells, the presented micromotor was expected to increase reversible electroporation yield, relative to standard electroporation, as only a small portion of the cell’s membrane (in contact with the micromotor) is affected. In contrast to methods in which the entire membrane of all cells within the sample are electroporated, the presented micromotor can perform, via magnetic steering, localized, spatially precise electroporation of the target cells that it traps and transports. In order to minimize nonselective electrical lysis of all cells within the chamber, resulting from extended exposure to an electrical field, magnetic propulsion was used to approach the immediate vicinity of the targeted cell, after which short-duration, electric-driven propulsion was activated to enable contact with the cell, followed by electroporation. In addition to local injection of fluorescent dye molecules, we demonstrated that the micromotor can enhance the introduction of plasmids into the suspension cells because of the dielectrophoretic accumulation of the plasmids in between the Janus particle and the attached cell prior to the electroporation step. Here, we chose a different strategy involving the simultaneous operation of many micromotors that are self-propelling, without external steering, and pair with cells in an autonomic manner. The locally electroporated suspension cells that are considered to be very difficult to transfect were shown to express the transfected gene, which is of significant importance for molecular biology research.

A Continuous Flow-through Microfluidic Device for Electrical Lysis of Cells

In contrast to the delicate 3D electrodes in the literature, a simple flow-through device is proposed here for continuous and massive lysis of cells using electricity. The device is essentially a rectangular microchannel with a planar electrode array built on its bottom wall, actuated by alternating current (AC) voltages between neighboring electrodes, and can be incorporated easily into other biomedical systems. Human whole blood diluted 10 times with phosphate-buffered saline (about 6 × 108 cells per mL) was pumped through the device, and the cells were completely lysed within 7 s after the application of a 20 V peak-to-peak voltage at 1 MHz, up to 400 μL/hr. Electric field and Maxwell stress were calculated for assessing electrical lysis. Only the lower half-channel was exposed to an electric field exceeding the irreversible threshold value of cell electroporation (Eth2), suggesting that a cross flow, proposed here primarily as the electro-thermally induced flow, was responsible for bringing the cells in the upper half-channel downward to the lower half-channel. The Maxwell shear stress associated with Eth2 was one order of magnitude less than the threshold mechanical stresses for lysis, implying that an applied moderate mechanical stress could aid electrical lysis.

Integration of marker-free selection of single cells at a wireless electrode array with parallel fluidic isolation and electrical lysis

We present integration of selective single-cell capture at an array of wireless electrodes (bipolar electrodes, BPEs) with transfer into chambers, reagent exchange, fluidic isolation and rapid electrical lysis in a single platform, thus minimizing sample loss and manual intervention steps.