A key step in many experimental workflows involves the counting of cells. Researchers often need to count cells prior to cell culture or before studying downstream processes and using analytical techniques that require an accurate and consistent number of input cells. Knowing the number of input cells is important for standardizing experiments and for measuring assay impact. Processes that require accurate and consistent numbers of input cells include transfection, cell proliferation or viability studies, and quantitative PCR. For researchers performing cell culturing, measuring the number of cells grown in tissue culture is essential to determine the level of confluence before diluting the cells into smaller aliquots for optimal cell growth.
This section provides an overview of the different cell counting methods and automated cell counters available, and mentions their advantages and disadvantages.
Related Topics: Transfection, Real-Time PCR and Multiplex Immunoassays.
Cell counting can be performed either by manually using a hemocytometer, or by using an automated cell counter. Read more on cell viability and cytotoxicity assays in the Protocols section below.
For over 100 years the hemocytometer has been used by cell biologists to count cells. It was first developed for the quantitation of blood cells but became a popular and effective tool for counting a variety of other cell types, particles, and even small organisms. Currently, hemocytometers equipped with improved Neubauer grids are a mainstay of cell biology labs. Cell counting using a hemocytometer suffers from a variety of shortcomings. These shortcomings include, but are not limited to, a lack of statistical robustness at low sample concentration, poor counts due to device misuse, and subjectivity of counts among users. In addition, cell counting using a hemocytometer is a time consuming and tedious operation.
You can find a manual cell counting protocol in the Protocols section below.
In recent years automated cell counting has become an attractive alternative to manual hemocytometer-based cell counting, offering more reliable results in a fraction of the time needed for manual counting.
Automated cell counters, such as the TC20™ automated cell counter, can provide a total count of mammalian cells and a live/dead ratio in a single step. Because there is no bias in counting, automated cell counters yield more accurate and reproducible results. Examples of processes that benefit from the speed and accuracy of automated cell counting include flow cytometry, toxicology studies, viral production, high content screening, and high content analysis.
Comparisons of count reproducibility, accuracy, and time to get results between a hemocytometer and the TC20 automated cell counter have been described in Hsiung et al. 2013 (Bio-Rad bulletin 6003).