Technical Notes: A Simple Technique for Reducing Edge Effect in Cell-Based Assays

Abstract

Several factors are known to increase the noise and variability of cell-based assays used for high-throughput screening. In particular, edge effects can result in an unacceptably high plate rejection rate in screening runs. In an effort to minimize these variations, the authors analyzed a number of factors that could contribute to edge effects in cell-based assays. They found that preincubation of newly seeded plates in ambient conditions (air at room temperature) resulted in even distribution of the cells in each well. In contrast, when newly seeded plates were placed directly in the CO 2 incubator, an uneven distribution of cells occurred in wells around the plate periphery, resulting in increased edge effect. Here, the authors show that the simple, inexpensive approach of incubating newly seeded plates at room temperature before placing them in a 37°C CO 2 incubator yields a significant reduction in edge effect. (Journal of Biomolecular Screening 2003:566-570)

High-Throughput Plasmodium falciparum Growth Assay for Malaria Drug Discovery

“…1), compounds and DMSO mock controls were added to microtiter plates containing complete medium. Next, synchronized ring-stage cultures were added to the microtiter plates in the presence and absence of compound, and the plates were incubated under a standard gas environment at 37°C for 72 h. Prior to incubation, the plates rested for 15 min to minimize the "edge effect" (13). Following the incubation period, DAPI DNA stain was added to detect the parasite DNA in infected erythrocytes.…”

Alternative Statistical Parameter for High-Throughput Screening Assay Quality Assessment

“…Cell-based assays often suffer from edge effects and can have an unacceptably high plate rejection rate. 6 However, a simple statistical method such as median polish has proven useful in adjusting for edge effects. Therefore, a plate with large variance due to the edge effect may no longer be a bad assay when we have the analysis tool to adjust for it.…”

Characterizing heterogeneous cellular responses to perturbations

“…For the time-course data, HeLa cells were diluted to 5,000 cells per 50 l of media and plated onto 384-well glass-bottom plates. Plates were incubated at room temperature for 30 min to minimize edge effects in wells (36), then placed in a 37°C/5% CO2 incubator overnight. Cells were fixed at 3, 6, 12, and 24 h after drug treatment.…”