A microfluidic system enabling continuous characterization of specific membrane capacitance and cytoplasm conductivity of single cells in suspension

This paper presents a microfluidic system enabling continuous characterization of specific membrane capacitance (C-specific membrane) and cytoplasm conductivity (sigma(cytoplasm)) of single cells in suspension. In this study, cells were aspirated continuously through a constriction channel while cell elongations and impedance profiles at two frequencies (1 kHz and 100 kHz) were measured simultaneously using microscopy imaging and a lock-in amplifier. 1 kHz impedance data were used to evaluate cellular sealing properties with constriction channel walls and 100 kHz impedance data were translated to quantify equivalent membrane capacitance and cytoplasm resistance of single cells, which were further translated to C-specific membrane and sigma(cytoplasm). Two model cell lines (kidney tumor cell line of 786-O (n = 302) and vascular smooth muscle cell line of T2 (n = 216)) were used to evaluate this technique, producing C-specific membrane of 3.67 +/- 1.00 and 4.53 +/- 1.51 mu F/cm(2) and sigma(cytoplasm) of 0.47 +/- 0.09 and 0.55 +/- 0.14 S/m, respectively. Compared to previously reported techniques which can only collect C-specific membrane and sigma(cytoplasm) from tens of cells, this new technique has a higher throughput, capable of collecting C-specific membrane and sigma(cytoplasm) from hundreds of cells in 30 min immediately after cell passage. (c) 2012 Elsevier B.V. All rights reserved.