Dielectric spectroscopy platform to measure MCF10A epithelial cell aggregation as a model for spheroidal cell cluster analysis

Abstract

3-Dimensional cell cultures are more representative of the native environment than traditional cell cultures on flat substrates. As a result, 3-dimensional cell cultures have emerged as a very valuable model environment to study tumorigenesis, organogenesis and tissue regeneration. Many of these models encompass the formation of cell aggregates, which mimic the architecture of tumor and organ tissue. Dielectric impedance spectroscopy is a non-invasive, label free and real time technique, overcoming the drawbacks of established techniques to monitor cell aggregates. Here we introduce a platform to monitor cell aggregation in a 3-dimensional extracellular matrix using dielectric spectroscopy. The MCF10A breast epithelial cell line serves as a model for cell aggregation. The platform maintains sterile conditions during the multi-day assay while allowing continuous dielectric spectroscopy measurements. The platform geometry optimizes dielectric measurements by concentrating cells within the electrode sensing region. The cells show a characteristic dielectric response to aggregation which corroborates with finite element analysis computer simulations. By fitting the experimental dielectric spectra to the Cole-Cole equation, we demonstrated that the dispersion intensity Δε and the characteristic frequency f are related to cell aggregate growth. In addition, microscopy can be performed directly on the platform providing information about cell position, density and morphology. This platform could yield many applications for studying the electrophysiological activity of cell aggregates.

Online monitoring of hiPSC expansion and hepatic differentiation in 3D culture by dielectric spectroscopy

“…These observations show that cell number expansion requires a few days to result in an increase of the aggregate biovolume and that each cell aggregate behaves as one overall inducible dipole. This relation was previously reported by Heileman and Tabrizian, stating that each cell in an aggregate contributes to increase the permittivity signal and that the aggregate polarization depends on the net contribution of their cells (Heileman & Tabrizian, 2017). Differences in the cell culture medium electrical properties, as the conductivity (Figure 2e), for sequential differentiation steps might also affect the measured cell permittivity leading to shifts and possibly drifts in the signal (Figure 2b, stage IV).…”

“…Finding process analytical technologies (PAT) that enable in situ monitoring of stem cell growth and differentiation status in 3D culture, thus minimizing contamination risks, would have an enormous impact in stem cell bioprocessing. Dielectric spectroscopy has already been shown to successfully monitor viable cell concentration in single‐cell suspension culture systems (Downey et al, 2014; Metze et al, 2020) but there are still few published applications in 3D cultures (Heileman & Tabrizian, 2017; Lei et al, 2014). Herein, we established an integrated bioprocess that combines 3D hiPSC expansion and hepatic differentiation steps in STB operating in perfusion and, for the first time, assessed the potential of dielectric spectroscopy for the in situ monitoring of hiPSC growth and differentiation status (Figure 1).…”

“…Finding process analytical technologies (PAT) that enable in situ monitoring of stem cell growth and differentiation status in 3D culture, thus minimizing contamination risks, would have an enormous impact in stem cell bioprocessing. Dielectric spectroscopy has already been shown to successfully monitor viable cell concentration in single-cell suspension culture systems (Downey et al, 2014;Metze et al, 2020) but there are still few published applications in 3D cultures (Heileman & Tabrizian, 2017;Lei et al, 2014).…”

Aberrant Water Structure Dynamics in B16 Melanoma-Bearing Mice by Time Domain Refractometry Analysis

“…Water structure analysis using dielectric spectroscopy revealed a higher ∆ ε value in surgically resected colon [ 14 , 15 ], liver [ 16 ] or brain [ 17 ] tumors, presumably, in part, reflecting the higher cellularity in tumor tissues, as with aggregated breast epithelial cells in 3D culture [ 27 ]. The remarkably high ∆ ε value of tumor tissue in the present study may reflect the crowded B16 melanoma cells and the interstitial cells like cancer-associated fibroblasts in the tumor microenvironment [ 28 ].…”

Electrical Impedance Measurements of Biological Cells in Response to External Stimuli

“…The dielectric properties of cells are major indicators of cell health, function, and stage. − Dielectric spectroscopy (DS) is widely used for analyzing the electrical properties of biological cells and can be used to examine and discriminate between tumor cells and healthy cells. Using impedance measurement techniques, drug resistant breast cancer cells (doxorubicin resistant MCF-7 DOX) may be distinguished from their parental cells (MCF-7 WT, wild-type) .…”