Problem: There is little doubt that cell-based assays are becoming a mainstay across the pre-clinical drug discovery process. Many of these assays are end-point based, where live cells are cultured in microplates, incubated with compounds of interest and then lysed to release the contents of the cell such that they can be assayed with reagents subsequently added to the wells. Often, the incubation times required for the assay can be counted in the minutes to decades of minutes, such that maintaining a controlled environment for cell health is not a significant concern. For those end-point assays that require longer incubation times of hours to decades of hours, controlled environments become a substantial concern and requirement. Depending on sample throughput required, this can be accomplished by manual intervention and placing the microplate(s) in a standard CO2 incubator or by robot into a microplate hotel.
Yet there is a growing trend in the use of live cell assays, where the cellular response to compounds is monitored kinetically through the use of non-toxic, cell membrane permeable reagents or phenotypic methods. This real-time response gives researchers an additional level of information that may be missed in single time point, end-point assay. While these live cell assays are easily incorporated into workflows for assays conducted over an hour or so, longer term responses can be problematic to obtain due to the difficulty in maintaining a controlled environment over the microplate to maintain cell health while kinetically reading the cellular response.