Ultra-Wideband Impedance Spectroscopy of a Live Biological Cell

For the first time, the impedance spectrum of a live Jurkat T-lymphocytes human cell was characterized in a single sweep, spanning six decades of frequency from 9 kHz to 9 GHz. The ultra-wide bandwidth bridged the traditional impedance spectroscopy at kilohertz-megahertz frequencies with the recently developed microwave dielectric spectroscopy, which can probe the cell interior without being hindered by the cell membrane. Based on the measured scattering parameters and a simple cell model, an equivalent circuit of four nondispersive elements, including membrane resistance, membrane capacitance, cytoplasm resistance, and cytoplasm capacitance, was extracted and found sufficient to explain the so-called β relaxation over the frequencies measured. These extracted cell parameters are in general agreement with the literature but are believed to be more accurate, giving the relatively small standard deviations, the configuration with a cell in intimate contact with the measurement electrodes, and the ultra-wide bandwidth of the measurement.