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 (Cspecific membrane) and cytoplasm conductivity (σcytoplasm) 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 Cspecific membrane and σcytoplasm. 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 Cspecific membrane of 3.67±1.00 and 4.53±1.51 μF/cm2 and σcytoplasm of 0.47±0.09 and 0.55±0.14 S/m, respectively. Compared to previously reported techniques which can only collect Cspecific membrane and σcytoplasm from tens of cells, this new technique has a higher throughput, capable of collecting Cspecific membrane and σcytoplasm from hundreds of cells in 30 min immediately after cell passage.

► We measure two-frequency impedance data of single cells in a constriction channel.
► Equivalent circuit models for impedance data interpretation are proposed.
► We quantify Cspecific membrane and σcytoplasm of cells based on data processing.
► Cspecific membrane and σcytoplasm from hundreds of cells per cell type are obtained.