Dielectric Properties of Single Cells Subjected to Heat Shock Using DEP Cytometry

Abstract

Dielectrophoresis (DEP) cytometry was used to investigate changes in the membrane capacitance, membrane conductance, and cytoplasm conductivity of single Chinese hamster ovary (CHO) cells subjected to thermal stress. CHO cells were exposed to temperatures ranging from 37 °C to 50 °C for 15 min and measured immediately after exposure. Heat-treated cells were measured at frequencies over the β-dispersion region to obtain the dielectric parameters of a multishell cell model. A microwave DEP cytometer measuring DEP-induced translation of many individual heat-treated cells at selected frequencies was used to determine the Clausius-Mossotti factor and subsequently cell dielectric parameters. Results reveal that temperatureinduced stress is accompanied by decrease in cell membrane capacitance from 1.75 to 0.71 μF/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> , suggesting alteration in morphological features of the cell membrane surface. Results also show an insignificant decline in cytoplasm conductivity for treatment up to 46 °C. A significant decline in cytoplasm conductivity, from an initial value of 0.34-0.22 S/m was observed for 50 °C. The effect of suspending cells in low-conductivity DEP media was also investigated.