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.

Li Huang, Li Xie, Jessica M. Boydb and Xing-Fang Li
Received 24th September 2007, Accepted 25th January 2008
First published as an Advance Article on the web 28th February 2008
DOI: 10.1039/b714384b

We report a new technique for the continuous and real-time measurement of microparticle-induced cellular responses using a real-time cell-electronic sensing (RT-CES) technology. The method involves the use of microelectrode-embedded microwells seeded with one of two lung cancer carcinoma cell lines (A549 and SK-MES-1), allowing for continuous measurements of impedance. The change in impedance that is automatically converted to the cell index is linearly correlated with the numbers of the seeding cells during the log phase, providing quantitative measurement of cytotoxicity. After 24 h of initial incubation in 96 microwells, the cultures are treated with microparticles, and changes in the cell index are monitored in real time. Multiple data, including dose response curves, IC50 (a concentration inhibiting 50% cell growth), and cell-specific and particulate-specific cell responses, are obtained from a single set of experiments. SK-MES-1 cells consistently showed more severe effects and lower IC50 values than A549 cells when they were treated with quartz particle suspensions. The different effects detected using the RT-CES technique were related to morphological change and apoptosis, supported by the scanning electronic microscopy and flow cytometry results. The method is further used to test the cytotoxicity of two PM10 standard reference materials of urban air dust and diesel particulates, demonstrating the potential application of this new technique for biomonitoring of air particulates.

Fu-Yue Zeng, Jimmy Cui, Lingling Liu, Taosheng Chen
Department of Chemical Biology and Therapeutics, St. Jude Children’s Research Hospital, 262 Danny Thomas Place, Mail Stop 1000, Memphis, TN 38105, USA
Cancer Letters xxx (2009) xxx–xxx

Patients with alveolar rhabdomyosarcoma (ARMS) have poorer response to conventional chemotherapy and lower survival rates than those with embryonal RMS (ERMS). By high-throughput screening, we identified camptothecin as an ARMS-selective inhibitor. Camptothecin more efficiently inhibited proliferation and induced apoptosis in Rh30 (ARMS) than RD (ERMS) cells. Ectopic expression of the PAX3–FKHR (PF) fusion protein in RD cells significantly increased sensitivity, whereas siRNA knockdown of PF decreased sensitivity of Rh30 cells to camptothecin. The sensitization required a transcriptionally active PF, and camptothecin downregulated levels of PF protein. These findings suggest that it is feasible to develop agents that preferentially block the growth of ARMS. 2009 Elsevier Ireland Ltd. All rights reserved.