As a researcher, you are aware of the central role of microtiter plates for your high-throughput screening campaigns. You might not, however, be aware of everything that goes into choosing the right microtiter plate, and how to fine-tune your selection. This article provides an overview of key application issues facing modern high-throughput screening campaigns and storage applications, including homogeneous, heterogeneous, and cell based assays, and the diverse capabilities of cell culture surfaces.
What are the biggest challenges in using microtiter plates in assays?
Choosing the right microtiter plate for an assay is a balancing act between multiple options and competing tradeoffs for each step, considering assay type, biology, technology, and throughput. [1-3] Countless microtiter plates from numerous suppliers are commercially available, and scientific publications often detail the specifications of the microtiter plate (e.g. catalog numbers) and detection systems, which can be a critical pairing to achieve the desired assay performance. [1] One could optimize endlessly, but in practice it is necessary to find a reasonable trade-off between understanding the quality of an assay system at each stage of the development or validation and the time required for microtiter plate selection.
Choosing the right surface for your application – cell free or cell based?
The decision to use a cell-free or cell-based assay is often the highest-yielding initial decision point in the microtiter plate selection process. [1] In addition, for cell culture applications, it must be decided whether cell attachment should be promoted or actively prevented ( e.g., to generate in vitro 3D cell models).
Compatibility with detection systems
The selected microtiter plate type must match the assay detection technology. Proper initial guidance is important to select the microtiter plate type for a particular detection technology and then fine-tune with the selected plates.
Throughput capabilities
The expected throughput of the assay must be considered. For example, the preferred density for screening assays may be 1536 wells, but automation of the assay may only be possible in 384 or 96 well plates. In this context, questions arise about the volume of the wells, affecting shaking efficiency and well meniscus, which can be critical components in certain detection systems.
Reproducibility of assay results
Regardless of assay type, reproducibility is often a challenge, and it is important to choose a manufacturer who can guarantee low lot-to-lot variation. Well-to-well variation and lack of uniformity of microtiter plate surfaces can also pose challenges, for example, wells at the edge of a microtiter plate may cause higher background signals due to stray light. In addition, edge effects can occur, i.e. signals that are either higher or lower than the signals in the center. This is due to thermal gradients and higher evaporation at the edge.
Keeping it contamination-free
Other challenges include well-to-well contamination, which can result from unclean pipetting, chemical compatibility of microtiter plates, and maintaining sterile conditions to prevent unwanted microorganisms from contaminating the assay.
Selecting well plate colors
The desired application usually determines the color of the microtiter plate. Transparent microplates are predominantly used for colorimetric assays and allow precise optical measurements due to their excellent optical properties. White pigmented microtiter plates are optimized for luminescence, and black pigmented plates for fluorescence measurements.
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References
[1] Auld DS Ph.D., Coassin PA B.S., Coussens NP Ph.D., et al. Microplate Selection and Recommended Practices in High-throughput Screening and Quantitative Biology. In: Markossian S, Grossman A, Brimacombe K, et al., eds. Assay Guidance Manual. Bethesda (MD): Eli Lilly & Company and the National Center for Advancing Translational Sciences; June 1, 2020. https://pubmed.ncbi.nlm.nih.gov/32520474/
[2] Greiner Bio-One Microplate Selection Guide https://www.gbo.com/fileadmin/media/GBO-International/01_Downloads_BioScience/SALES_Brochures/English/F073048_microtiter plate _Selection_Guide_EN.pdf
[3] Microplates for Enzyme Linked Immunosorbent Assays (ELISA). Greiner Bio-One forum – Technical Notes and Applications for Laboratory Work https://www.gbo.com/fileadmin/media/USA/01_Downloads_BioScience/SALES_Scientific_Publications/F073004_Forum_No._09_ELISA.pdf