Roche Applied Science's Xcelligence RTCA HT instrument allows users to perform fully automated impedance screens for GPCRs and other targets in the 384-well high-throughput format.
Label-free technologies have entered the stage of cellular drug discovery and high-throughput screening (HTS).
For the measurement of G protein-coupled receptor (GPCR) activation electrical impedance represents a good universal readout technology, since different signalling pathways can be measured in one assay format using recombinant as well as primary cells.
In a recent case study, Urs Luthi and John Gatfield from Actelion Pharmaceuticals integrated two RTCA HT (real-time cell analyser for high-throughput) instruments on an automated high-throughput screening platform from Agilent Technologies.
Two hundred and sixty three hits of the orexin type 1 (Ox1) GPCR that had been identified in a classical calcium flux (FLIPR) HTS were screened for Ox1 inhibition in fully automated RTCA HT assays.
The overall performance, the quality of E-Plates 384 and intra- and inter-assay reproducibility were evaluated.
Sixty-five per cent of the 263 antagonist hits were confirmed to be Ox1 receptor antagonists after impedance measurements.
According to the researchers, the RTCA HT instrument could be readily integrated into automated workflows and delivered a highly reproducible dataset, making the RTCA HT instrument a powerful screening technology.
Compared with standard readout technologies, one of the advantages of label-free technologies is that cellular processes are measured in real-time kinetics in a non-invasive manner.
The Xcelligence system uses gold electrodes at the bottom surface of microplate wells as sensors to which an alternating current is applied.
Cells that are grown as adherent monolayers on top of such electrodes influence the alternating current at the electrodes by changing the electrical resistance (impedance).
The degree of this change is primarily determined by the number of cells, strength of the cell-cell interactions, interactions of the cells with the microelectrodes and by the overall morphology of the cells.
