Abstract
Electrical lysis of biological cells on a microfluidic platform has been raising a lot of interests due to its applications in rapid recovering intracellular contents without introducing lytic agents. Most of previous reports on micro fluidic electrical lysis were demonstrated applying alternating current (AC) or pulsed direct current (DC) fields. Typically microscale electrodes or structures with dimensions comparable to those of cells were implemented. Applying a DC field for cell lysis typically requires a field strength of 1-10 kV/cm which is dependent on the cell species. Bubble generation and Joule heating can often be induced under such high field strengths. These make continuous high throughput operations challenging. In this study, we demonstrated a simple microfluidic device which lysed green fluorescent protein (GFP) expressing E. coli cells under continuous DC voltage while cells flowed through. The cell lysis only happened in a defined section of a microfluidic channel due to the local field amplification by geometric modification. The geometric modification also effectively decreased the required voltage for lysis by several folds. We found that a local field strength of 1500V/cm was required for lysis of nearly 100% of E. coli cells. This lysis field strength was considerably lower than the value reported in the literature, possibly due to the longer duration of the field. The lysis was witnessed by plate count and fluorescence spectroscopy. The devices were fabricated using low-cost soft lithography with channel widths considerably larger than the cell size to avoid clogging and ensure stable performance. Our tool will be ideal for high throughput processing of a large number of cells. Furthermore, the application of continuous DC field makes it straightforward to couple our cell lysis device with on-chip electrophoresis to realize the integration of cell pretreatment and chemical analysis. In principle, the same approach can also be applied for the lysis of mammalian cells and for the electroporation and transfection.