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

Abstract

The study and the characterization of cell death mechanisms are fundamental in cell biology research. Traditional death/viability assays usually involve laborious sample preparation and expensive equipment or reagents. In this work, we use electrical impedance spectroscopy as a label-free methodology to characterize viable, necrotic and apoptotic human lymphoma U937 cells. A simple three-electrode coplanar layout is used in a differential measurement scheme and thousands of cells are measured at high-throughput (≈200 cell/s). Tailored signal processing enables accurate and robust cell characterization without the need for cell focusing systems. The results suggest that, at low frequency (0.5 MHz), signal magnitude enables the discrimination between viable/necrotic cells and cell fragments, whereas phase information allows discriminating between viable cells and necrotic cells. At higher frequency (10 MHz) two subpopulations of cell fragments are distinguished. This work substantiates the prominent role of electrical impedance spectroscopy for the development of next-generation cell viability assays.

A neural network approach for real-time particle/cell characterization in microfluidic impedance cytometry

“…To increase the richness of cell characterization, electric phase information or higher stimulation frequencies can be considered, for instance, to retrieve information related to cell viability, plasma membrane morphology, or intracellular properties [21,[46][47][48]. Moreover, additional sensing zones can be introduced able to provide cell shape indicators [8,49].…”

Positional dependence of particles and cells in microfluidic electrical impedance flow cytometry: origin, challenges and opportunities

“…Moreover, this system also provides the ability to discriminate beads from yeasts despite the similar size, as well as two yeast populations. It has been reused in 2019 by De Ninno et al 134 for highthroughput label-free discrimination of viable, necrotic and apoptotic human lymphoma U937 cells. This work exploited multifrequency measurements together with impedance data correction using an impedance-based metric correlated with cell height.…”

“…In some cases, according to the degree of heterogeneity of the population of interest, the reduction of the dispersion of the impedance data among each subpopulation may still not be enough to distinctly separate them. In other words, the mitigation of the impact of particle position on the measured impedance is not sufficient to completely remove the overlap of the data from different subpopulations 134 . Multi-frequency measurements can be done to provide informations on the dielectric properties of several components of the cells in addition to its morphological features 113 .…”

Review: Dielectrophoresis in cell characterization

“…Other on‐chip methods to assess cell electrophysiology, such as impedance cytometry, allow for single‐cell analysis [30–33], however, early methods’ resolution and accuracy were affected by the positional dependence of the signal and did not offer significant throughput. Current strategies to implement cell focusing and microfluidics to meet these challenges are often complex or optimized for a particular cell size [34–36]. Recent work has shown a marked increase in throughput from less than 100 cells/s to reports of over 300 cells/s [35–37].…”

“…Current strategies to implement cell focusing and microfluidics to meet these challenges are often complex or optimized for a particular cell size [34–36]. Recent work has shown a marked increase in throughput from less than 100 cells/s to reports of over 300 cells/s [35–37]. Further, results have compared well to DEP measurements taken in parallel [37].…”