Cellular Dielectric Spectroscopy: A Powerful New Approach to Label-Free Cellular Analysis

Abstract

The past decade has seen a number of significant changes in identifying higher quality lead compounds earlier in the drug discovery process. Cell-based assay technologies yielding high-content information have emerged to achieve this goal. Although most of these systems are based on fluorescence detection, this article describes the development and application of an innovative cellular assay technology based on radio frequency spectrometry and bioimpedance measurements. Using this technique, the authors have discovered a link between cellular bioimpedance changes and receptor-mediated signal transduction events. By performing dielectric spectroscopy of cells across a spectrum of frequencies (1 KHz to 110 MHz), a series of receptorspecific, frequency-dependent impedance patterns is collected. These raw data patterns are used to determine the identity of the cellular receptor-signaling pathway being tested and to quantify stimulation endpoints and kinetics. The authors describe the application of this technology to the analysis of ligand-induced cellular responses mediated by the 3 major classes of Gprotein-coupled receptors (GPCRs) and protein tyrosine kinase receptors. This single assay platform can be used with ease to monitor G s , G i , and G q GPCRs without the need for chimeric or promiscuous G-proteins, fluorophors, or tagged proteins. In contrast to other methods of monitoring cellular signal transduction, this approach provides high information content in a sim-

Evaluation of Cellular Dielectric Spectroscopy, a Whole-Cell, Label-Free Technology for Drug Discovery on Gi-Coupled GPCRs

“…1,[3][4][5][6] For GPCRs, CDS assays offer several potential advantages that are substantial improvements over existing technologies. CDS is applicable to each of the 3 major G-protein coupled pathways.…”

Chip Based Electroanalytical Systems for Cell Analysis

“…Another contribution demonstrating high-throughput capabilities of cell impedance measurements comes from MDS Sciex producing the CellKey system. Published applications, using 96-well platforms in the system comprising fluid and temperature control, have described evaluation of GPCRs [164] and additionally tyrosine kinase receptors [165] in several different cell lines. The measurements are conducted using a pair of IDEs in each well at 24 different frequencies in the range of 1 kHz to 10 MHz, according to a protocol termed cellular dielectric spectroscopy (CDS).…”

Interdigitated impedance sensors for analysis of biological cells in microfluidic biochips

“…Dielectric spectroscopy makes use of the electrical properties of cells exposed to a small magnitude (AE15 mV) radio-frequency electrical field (Yardley et al, 2000). Dielectric spectroscopy has proven useful for analyzing biological cell suspensions to study cell sedimentation, cell aggregation, cell division and growth rates of low density liquid cultures (volume fraction below 0.15) (Ehret et al, 1998;Prodan et al, 2004;Asami, 2002;Polevaya et al, 1999;Ciambrone et al, 2004).…”