Atienza JM, Yu N, Kirstein SL, Xi B, Wang X, Xu X, Abassi YA.
Assay Drug Dev Technol. 2006 Oct;4(5):597-607. Review.

Lisa Minor, Ph.D. Vascular Research Team Johnson & Johnson PRD
American Drug Discovery. September 2007

Wouldn't it be ideal to measure cellular events to different cellular stimuli using a common assay methodology without having to modify the cellular environment by addition of endogenous labels, i.e. using labelfree technology, and do it in real time in a living cell? Labelfree technologies based on electrical impedance or refractive index offers such scenarios. This article will describe these technologies and their application to cell-based assays, their potential value in high throughput screening, directed screening and secondary assays as well as evaluate their possible drawbacks.

Biao Xi, Naichen Yu, Xiaobo Wang, Xiao Xu and Yama A. Abassi
ACEA Biosciences, San Deigo, CA, USA
Biotechnology Journal 2008,3,,484-495

Cell-based assays are an important part of the drug discovery process allowing for interrogation of targets and pathways in a more physiological setting compared to biochemical assays. One of the main hurdles in the cell-based assay field is to design sufficiently robust assays with adequate sig- nal to noise parameters while maintaining the inherent physiology of the pathway or target being investigated. Conventional label and reporter-based cell assays may be more prone to artifacts due to considerable manipulation of the cell either by the label or over-expression of targets or reporter proteins. Cell-based label-free technologies preclude the need for cellular labeling or over-expres sion of reporter proteins, utilizing the inherent morphological and adhesive characteristics of the cell as a physiologically relevant and quantitative readout for various cellular assays. Furthermore, these technologies utilize non-invasive measurements allowing for time resolution and kinetics in the assay. In this article, we have reviewed the various label-free technologies that are being used in drug discovery settings and have focused our discussion on impedance-based label-free tech- nologies and its main applications in drug discovery.