From Cellular Cultures to Cellular Spheroids: Is Impedance Spectroscopy a Viable Tool for Monitoring Multicellular Spheroid (MCS) Drug Models?

Abstract

The use of 3-D multicellular spheroid (MCS) models is increasingly being accepted as a viable means to study cell-cell, cell-matrix and cell-drug interactions. Behavioral differences between traditional monolayer (2-D) cell cultures and more recent 3-D MCS confirm that 3-D MCS more closely model the in vivo environment. However, analyzing the effect of pharmaceutical agents on both monolayer cultures and MCS is very time intensive. This paper reviews the use of electrical impedance spectroscopy (EIS), a label-free whole cell assay technique, as a tool for automated screening of cell drug interactions in MCS models for biologically/physiologically relevant events over long periods of time. EIS calculates the impedance of a sample by applying an AC current through a range of frequencies and measuring the resulting voltage. This review will introduce techniques used in impedance-based analysis of 2-D systems; highlight recently developed impedance-based techniques for analyzing 3-D cell cultures; and discuss applications of 3-D culture impedance monitoring systems.

Organic electrochemical transistors for cell-based impedance sensing

“…EIS is a technique which has long been used to determine mechanisms of reactions occurring at electrode/electrolyte interfaces. 3 A standard EIS experiment applies a small AC bias across a material or system under investigation and measures the output current response over a specific frequency range. EIS is particularly compatible with biological systems because of the low voltages applied (typically <50 mV).…”

“…EIS is particularly compatible with biological systems because of the low voltages applied (typically <50 mV). 3 EIS was first demonstrated for monitoring cell attachment and spreading on electrodes in the 1980s and was explained as changes in impedance due to the presence of cells on or near the electrodes. [4][5][6] In biological samples, the resistive portion (R) of the impedance is assumed to be affected by factors that would limit the ability of ions to migrate during application of an electric field, i.e., by insulating cell membranes or cell junctions which block the flow of ions.…”

Towards Bio-impedance Based Labs: A Review

“…In some applications, there are only capacitive path signal between the electrode-sample, so R ct resistance can be rejected. At some others, the model must be matched to the biological sampled being measure, as for example, measuring impedance of tissues [23], cell cultures [29], or cell density in suspension 3D [27], due to particular relationship observed between the electrodes and the bio-samples. In the electrode biosample modelling field, alternative setups and methodologies for LoC system are currently being explored [3].…”

Research Update: Electrical monitoring of cysts using organic electrochemical transistors

“…Some of the techniques, which are applicable for monitoring 2D cultures, such as immunofluorescence, can be used for monitoring 3D cultures; however, a majority of techniques developed for 2D cultures are not adapted for 3D cultures. 8 One particularly promising method for assessing tissues in vitro is electrical impedance spectroscopy (EIS). EIS is an extremely effective means of monitoring tissues in vitro with key advantages including the ability to monitor continuously the response to different stimuli over time, and also the label-free nature of the technique without recourse to fluorophores or chromophores.…”

“…9 A number of commercially available EIS systems exist in a variety of different formats which can be roughly divided into two categories; the planar format where cells are grown directly on the top of two electrodes, and the non-planar format, where cells are grown in single or multiple layers on a porous support and electrodes are placed on either side of the cell culture. 8,10 However, the commercial EIS formats are incompatible with 3D cyst/spheroid cultures, because it is necessary to isolate the spheroid in order to lead the current from one electrode through the spheroid rather than around it. Two exceptions are the work by Poenick et al where a planar-type microcavity approach was used, with cells sitting on the microelectrodes, and that by Thielecket et al where spheroids were isolated in capillary chambers and then the impedance was measured using a commercial impedance analyzer; however, in both cases, the cultures were relatively large spheroids (∼300 µm diameter).…”