Rapid determination of the electroporation threshold for bacteria inactivation using a lab-on-a-chip platform.

Electroporation based locally enhanced electric field treatment (LEEFT) is an emerging bacteria inactivation technology for drinking water disinfection. Nevertheless, the lethal electroporation threshold (LET) for bacteria has not been studied, partly due to the tedious work required by traditional experimental methods. Here, a lab-on-a-chip device composed of platinum electrodes deposited on a glass substrate is developed for rapid determination of the LET. When voltage pulses are applied, an electric field with a linear strength gradient is generated on a channel between the electrodes. Bacterial cells exposed to the electric field stronger than the LET are inactivated, while others remain intact. After a cell staining process to differentiate dead and live bacterial cells, the LETs are obtained by analyzing the fluorescence microscopy images. Staphylococcus epidermidis has been utilized as a model bacterium in this study. The LETs range from 10 kV/cm to 35 kV/cm under different pulsed electric field conditions, decreasing with the increase of pulse width, effective treatment time, and pulsed electric field frequency. The effects of medium properties on the LET were also investigated. This lab-on-a-chip device and the experimental approach can also be used to determine the LETs for other microorganisms found in drinking water.