With significant resources and money being invested in the identification of lead compounds in the drug screening process, it is critical that researchers have a highly efficient, reliable, and often automated method of culturing cells for various cellular assays. As such, the culture plate and its ability to integrate with automated systems is key to streamlining an effective high-throughput process.
However, the commonly experienced “edge effect” can often impact on data consistency. The evaporation of medium from wells during incubation is especially prominent in the wells closest to the perimeter of the plate (the edge wells) and results in well-to-well variations. As medium evaporates, concentrations are consequently altered, and cell growth is adversely affected.
Differential evaporation across the plate results in variability; a volume loss as small as 10% concentrates media components and metabolites enough to alter cell physiology and, in some cases, this can be quite severe. Furthermore, plates are often not optimized for imaging purposes, making it difficult to obtain clearly focused fields. As a result, the plate cannot be used efficiently.
In an attempt to alleviate the edge effect, researchers often decide not to culture cells in the outermost wells but to fill these with sterile water, and use only the inner wells of each plate for cell cultures. By rendering these wells unusable, throughput and, therefore, efficiency, is substantially reduced. The additional difficulties of obtaining clearly focused field images also hinders throughput since multiple screenings may need to be performed in order to obtain usable results.
Thermo Fisher Scientific recently developed a novel plate design that incorporates a large evaporation buffer zone (or moat) built into its perimeter, which can be filled with sterile water. Alternatively, through the inclusion of 0.5% agarose, for example, the moat is provided with a solid, jelly-like material to eliminate spillages, making it usable as a stand-alone plate or as part of a fully automated workflow. In this article, the effects of the moat on well-to-well variability in cell growth and overall plate evaporation are reviewed. In addition, the effect of an extremely flat plate on eliminating blur in imaging applications is investigated.