Choosing an Automated Cell Counting System
The simplest device for cell counting has been the hemacytometer or hemocytometer used with a standard light microscope. The hemocytometer has been the main instrument for counting cells since the 1800’s, and have evolved several times for two centuries. However, various issues are commonly known such as the operation is time-consuming and tedious, as well as variability that can result from operator errors. An automated cell counting system can be used to detect the biological phenomenon and signals from your measurands (cells) and probes. The cell counting system consists of not only the instrument, but also the reagents, consumables, and software algorithms for cell identification. By considering the different components of the cell counting system, an optimal selection can be made for the selected cell counting assay. The table below demonstrates examples of specific cell counting systems comprising instrument, reagents, consumable and software algorithm from Nexcelom Bioscience.
A critical consideration for any cell counting instrument is the range without dilution. Some instruments may indicate a large cell concentration range, but may require multiple dilutions, which can increase the Coefficient of Variation (CV) of the cell counting results. Therefore, it is important to know the actual cell counting range in the absence of any dilution steps (Figure 8). Demonstration of this concept is observed in an experiment performed by measuring cell count and viability of lymphocytes from 30 different mice using the acridine orange/propidium iodide. The Cellometer Auto 2000 showed that mouse lymphocytes can be properly measured within a range from 1 x 105 to 6 x 107 cells/mL without additional dilution steps (Table 3). Therefore, researchers can reliably use automated cell counting instrumentation to measure within this range, thus avoiding dilution as a confounding factor.
Beyond dilution range, there are multiple additional factors when choosing a cell counting system, including what reagents and consumables are required. While reagents can affect cell counting itself through the type, fluorescence color, or strength of signal, they also can affect general experimental flow through cost, availability, and ease of access. Additional consumable considerations include sterility and reusability, as well as shelf-life. Finally, researchers must carefully consider the software used to count cells, as algorithms between systems can vary drastically. The system software should be able to accurately assess the desired measurand, which may include many considerations for the usability of the software. Ultimately, the cell counting system chosen will be specific to the sample and desired result and should be made with consideration to long-term consistency, especially when considering manufacturing applications.