Comparing Label-Free Biosensors for Pharmacological Screening With Cell-Based Functional Assays

Abstract

The diversity and impact of label-free technologies continues to expand in drug discovery. Two classes of label-free instruments, using either an electrical impedance-based or an optical-based biosensor, are now available for investigating the effects of ligands on cellular targets. Studies of GPCR function have been especially prominent with these instruments due to the importance of this target class in drug discovery. Although both classes of biosensors share similar high sensitivity to changes in cell shape and structure, it is unknown whether these biosensors yield similar results when comparing the same GPCR response. Furthermore, since cell morphology changes induced by GPCRs differ depending on which G-protein is activated, there is potential for these instruments to have differential sensitivities to G-protein signaling. Here 1 impedance (CellKey)- and 2 optical-based instruments (BIND and Epic) are compared using Gi-coupled (ACh M2), Gq-coupled (ACh M1), and Gs-coupled (CRF1) receptors. All 3 instruments were robust in agonist and antagonist modes yielding comparable potencies and assay variance. Both the impedance and optical biosensors showed similar high sensitivity for detecting an endogenous D1/D5 receptor response and a melanocortin-4 receptor inverse agonist (agouti-related protein). The impedance-based biosensor was uniquely able to qualitatively distinguish G-protein coupling and reveal dual signaling by CRF1. Finally, responses with a ligand-gated ion channel, TRPV1, were similarly detectable in each instrument. Thus, despite some differences, both impedance- and optical-based platforms offer robust live-cell, label-free assays well suited to drug discovery and typically yield similar pharmacological profiles for GPCR ligands.

Tricyclic Antidepressant Amitriptyline-induced Glial Cell Line-derived Neurotrophic Factor Production Involves Pertussis Toxin-sensitive Gαi/o Activation in Astroglial Cells

“…This study demonstrated that the PTX-sensitive G i/o subunits, especially G o and G i3 , play important roles in the activation of ERK evoked by amitriptyline. The CellKey TM assay confirmed the pharmacological and siRNA findings, in that the pattern of the change in impedance induced by amitriptyline was similar to that of activation of G i/o -coupled receptors, and not of G s -or G q -coupled receptors (13,14,17,18). Although the C6 cells is an astrocyte model cell line derived from rat glioma, activation of the MMP/FGFR/FRS2␣/ERK cascade occurs in both normal human and rat astrocytes as well (9,11), in a PTX-sensitive manner.…”

“…The effect of amitriptyline on G protein activation in living C6 cells and rat astrocytes was analyzed using a novel biosensor technology, the CellKey TM assay (MDS Sciex, Ontario, Canada). The CellKey TM assay utilizes cellular dielectric spectroscopy, which is specifically tailored to G protein-coupled receptor (GPCR) detection and can distinguish signals between the G␣ s (G s ), G␣ i/o (G i/o ), and G␣ q (G q ) subfamilies (13,14).…”

History of the G Protein–Coupled Receptor (GPCR) Assays From Traditional to a State-of-the-Art Biosensor Assay

“…Cellular dielectric spectroscopy (CDS) is a novel technology that utilizes a label-free, real-time and cell-based assay approach and enables comprehensive pharmacological evaluation of cells that exogenously or endogenously express receptors (20,21). This technology is universal and allows the measurement of multiple types of receptors, including GPCRs, tyrosine kinase receptors, and nuclear receptors on the same platform without any modification of the cells (20,21).…”

“…This technology is universal and allows the measurement of multiple types of receptors, including GPCRs, tyrosine kinase receptors, and nuclear receptors on the same platform without any modification of the cells (20,21). CDS is classified into two types, an optical-based biosensor and an electrical impedance-based biosensor (3).…”

Resonant waveguide grating imager for live cell sensing

“…[4][5][6][7][8][9][10][11] Conventional systems employ a stationary array of fiber optics to repetitively scan a microtiter plate. 12 As a result, only cells along the scanning path ͑ϳ100 m in width͒ are sampled to generate an averaged response.…”