Electrical impedance tomography for real-time and label-free cellular viability assays of 3D tumour spheroids

Abstract

There is currently a need to culture cells in 3D to better mimic the behaviour of cells growing in the natural environment. In parallel, this calls for novel technologies to assess cell growth in 3D cell culture. In this study, we demonstrated both in silico and in vitro that cell viability inside large cell spheroids could be monitored in real time and label-free with electrical impedance tomography (EIT). Simulations using a single shell model and the effective media approximation (EMA) method were performed to prove the performance of EIT on spheroid imaging and viability monitoring. Then in vitro experiments were conducted to measure in real time a loss of cell viability in MCF-7 breast cancer spheroids when exposed to Triton X-100 and validate with conventional biochemical assays. It is shown that EIT has a spatial resolution of 1.14% and it could monitor the cell mortality over 20% of a spheroid under laboratory noise level. The reconstructed conductivity images for cell mortality induced by the chemical are clear and match the result in the cellular metabolic viability assay. Furthermore, the image reconstruction speed in the experiment was less than 0.3 seconds. Taken together, the results show the potential of EIT for non-destructive real-time and label-free cellular assays in the miniature sensor, providing physiological information in the applications of 3D drug screening and tissue engineering.

Three‐Dimensional (3D) cell culture monitoring: Opportunities and challenges for impedance spectroscopy

“…The successful use of EIT as a medical diagnostic and its ability to obtain in vivo information, suggests that it may be an effective monitoring technique for future 3D cell cultures. Researchers have demonstrated the measurement of 3D tissue impedance and subsequently reconstruction of the respective images using EIT (Jamil et al, 2016; Wu, Yang, Bagnaninchi, & Jia, 2017; Wu, Yang, Bagnaninchi, & Jia, 2018; Wu, Zhou, Yang, Jia, & Bagnaninchi, 2018; Yang et al, 2017; Yin, Wu, Jia, & Yang, 2018; Yin, Yang, Jia, & Tan, 2017). For monitoring 3D cell aggregates or spheroids, two electrode distribution designs were implemented.…”

“…(b) Rectangular electrodes at the boundary of the well were used to monitor spheroid and (c) reconstructed images for the spheroid samples in 2% Triton X‐100 solution (1‐2) and HG culture medium (3–4). Reproduced with permission (Wu, Yang et al, 2018; Wu, Zhou et al, 2018). Copyright Wu et al (2018) [Color figure can be viewed at wileyonlinelibrary.com]…”

Application of Impedance-Based Techniques in Hepatology Research

“…Combining 3D in vitro human models with impedance based cellular assays will provide a platform for a non-invasive, quantitative, detailed analysis of cell culture in real time, hugely benefiting the in vitro drug screening process and making animal testing less attractive. Recent developments in microelectrode sensor design for electrical impedance tomography show great promise in their translation to the field of tissue engineering and 3D culture [70][71][72].…”

Applications of bioimpedance measurement techniques in tissue engineering

“…However, fluorescent staining normally kills the cells. On the other hand, the penetration depth of the commonly employed techniques for 2D cell cultures such as confocal and fluorescence microscopies, are limited (<50 micrometers) (53). Therefore, as an alternative approach for real-time and non-invasive and label-free measurements, bioimpedance measurement techniques can be applied (54).…”