Extending In-Plane Impedance Measurements from 2D to 3D Cultures: Design Considerations.

Sorel E De Leon,Paul R Stoddart,Zay Yar Oo,Sally L Mcarthur,Lana Cleuren

doi:10.3390/bioengineering8010011

Abstract

Three-dimensional (3D) cell cultures have recently emerged as tools for biologically modelling the human body. As 3D models make their way into laboratories there is a need to develop characterisation techniques that are sensitive enough to monitor the cells in real time and without the need for chemical labels. Impedance spectroscopy has been shown to address both of these challenges, but there has been little research into the full impedance spectrum and how the different components of the system affect the impedance signal. Here we investigate the impedance of human fibroblast cells in 2D and 3D collagen gel cultures across a broad range of frequencies (10 Hz to 5 MHz) using a commercial well with in-plane electrodes. At low frequencies in both 2D and 3D models it was observed that protein adsorption influences the magnitude of the impedance for the cell-free samples. This effect was eliminated once cells were introduced to the systems. Cell proliferation could be monitored in 2D at intermediate frequencies (30 kHz). However, the in-plane electrodes were unable to detect any changes in the impedance at any frequency when the cells were cultured in the 3D collagen gel. The results suggest that in designing impedance measurement devices, both the nature and distribution of the cells within the 3D culture as well as the architecture of the electrodes are key variables.

Highlights

Standard cell culture methodology involves growing cells in a flask with a flat surface and letting them attach and proliferate on this area
There are a range of approaches to 3D cell culture, each with their own specific properties
It was observed that in 3/4 of the samples there was no clear change in the signal from the wells containing cells compared to the control in either the magnitude or the phase spectra

Summary

Introduction

Standard cell culture methodology involves growing cells in a flask with a flat surface and letting them attach and proliferate on this area. 3D cell culture has been able to replicate many aspects of in vivo cell biology [1,2,3]. There are a range of approaches to 3D cell culture, each with their own specific properties. Cells can be maintained in suspension and driven to form a spheroid, or using tissue samples and stem cell biology they can be differentiated to form organoids that replicate the cell diversity found in organs like the kidney. Both of these systems have been shown to be highly effective for testing both basic biological function and drug interactions. When drugs are tested in 3D, it has been shown that the expression levels of drug-metabolising enzymes resemble that of native tissue [2,3]

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