Label-free single cell analysis with a chip-based impedance flow cytometer

Abstract

For description of cellular phenotypes and physiological states new developments are needed. Axetris' impedance flow cytometer (IFC) (Leister) is a new promising label-free alternative to fluorescence-based flow cytometry (FCM). IFC measures single cells at various frequencies simultaneously. The frequencies used for signal acquisition range from 0.1 to 20 MHz. The impedance signal provides information about cell volume (< 1 MHz), membrane capacitance (~1-4 MHz) and cytoplasmic conductivity (4-10 MHz), parameters directly related to the physiological conditions of single cells. In MCF-7 cell viability experiments, cells were treated with cytotoxic agents to induce cell death. Impedance analysis showed discrimination between viable and dead cells. This was clearly visible at 4 MHz suggesting that differentiation was possible based on cell membrane capacitance. Changes in cell membrane potential were also analysed by IFC. RN22 cells were loaded with membrane potential sensitive dye (DiBAC4). The cells were then treated with the ionophore valinomycin. Changes in membrane potential were detectable at the level of cytoplasm conductivity (>4 MHz) and membrane capacitance (1-4 MHz). Our data indicate that IFC can be a valuable alternative to conventional FCM for various applications in the field of cell death and physiology. The work will be extended to address further potential applications of IFC in biotechnology and biomedical cell analysis, as well as in cell sorting.

A microfluidic biochip for complete blood cell counts at the point-of-care

“…has shown the total leukocyte count and its differential using multi-frequency analysis 7 . Most of the above mentioned microfluidic counters were based on impedance cell counting technology 14,15 . Nguyen et al .…”

Microfluidic CD4 + and CD8 + T Lymphocyte Counters for Point-of-Care HIV Diagnostics Using Whole Blood

“…Owing to simplicity and low cost, electrical detection methods hold much promise for POC cytometry. Much progress has been made in impedance microcytometry with alternating current interrogation to detect differences in chemically modified cells (16)(17)(18) and cells infected with parasites (17), and to discriminate among cell types (19)(20)(21)(22). Nevertheless, impedance microcytometry still has not proven to be sensitive enough to distinguish among cells that have similar morphologies, such as lymphocyte subclasses and monocytes.…”

High-throughput label-free characterization of viable, necrotic and apoptotic human lymphoma cells in a coplanar-electrode microfluidic impedance chip

“…This cluster exhibits a different low-frequency phase Φ 0.5 with respect to cluster L 1 of the control sample. Since the electric phase depends on cell membrane properties (Pierzchalski et al, 2010), this suggests that cluster L 2 corresponds to cell with altered plasma membrane, most probably necrotic cells.…”