Niels Haandbæk

Time-lapse electrical impedance spectroscopy for monitoring the cell cycle of single immobilized S. pombe cells.

As a complement and alternative to optical methods, wide-band electrical impedance spectroscopy (EIS) enables multi-parameter, label-free and real-time detection of cellular and subcellular features. We report on a microfluidics-based system designed to reliably capture single rod-shaped Schizosaccharomyces pombe cells by applying suction through orifices in a channel wall. The system enables subsequent culturing of immobilized cells in an upright position, while dynamic changes in cell-cycle state and morphology were continuously monitored through EIS over a broad frequency range. Besides measuring cell growth, clear impedance signals for nuclear division have been obtained. The EIS system has been characterized with respect to sensitivity and detection limits. The spatial resolution in measuring cell length was 0.25 μm, which corresponds to approximately a 5-min interval of cell growth under standard conditions. The comprehensive impedance data sets were also used to determine the occurrence of nuclear division and cytokinesis. The obtained results have been validated through concurrent confocal imaging and plausibilized through comparison with finite-element modeling data. The possibility to monitor cellular and intracellular features of single S. pombe cells during the cell cycle at high spatiotemporal resolution renders the presented microfluidics-based EIS system a suitable tool for dynamic single-cell investigations.

Development of a Microfluidic GHz Impedance Cytometer

Abstract This article presents a novel microfluidic impedance cytometer enabling dielectric characterization of single cells at frequencies up to 500 MHz. The dielectric properties of cells at lower frequencies contain information about their size and membrane capacitance. The increased frequency range of the presented cytometer potentially allows for characterization of intracellular components, such as vacuoles or the cell nuclei. We demonstrate the overall capabilities of the cytometer through discrimination of polystyrene beads from Chinese hamster ovary (CHO) cells. The discrimination is based on the difference in dielectric properties at frequencies up to 500 MHz.