Hunch over a microscope for a few hours to count blood cells with a hemocytometer and— other than a neck massage—you will want only one thing: an automated cell counter. Fortunately, automated cell counters can be procured more easily than ever, because introductory models keep dropping in price. “What used to cost more than $5,000 and require expensive single-use consumables now costs only around $2,000, like the Countess II, or is available with a reusable-slide option, like the Countess II FL, to reduce run-rate cost—both of which are customer-critical features,” says Stephen Full, product manager for biosciences and cellular analysis at Thermo Fisher Scientific.
Beyond improving economics, automated cell counters offer enhanced features, such as fluorescent capabilities. “While fluorescence has been rooted in cell biology labs for some time,” Full explains, “the ability to easily assess fluorescent properties of cell samples during traditional culture-to-experiment workflow has never been cheaper, easier or more flexible.”
When asked about the most interesting recent applications of automated cell counting, Neon Jung, CEO at South Korea-based Logos Biosystems, says, “Definitely, it is bacterial cell counting.” In most cases, scientists analyze bacteria by counting colonies. Nonetheless, says Jung, “There have been growing needs to count bacteria directly on a single-cell level for faster decision making.” This can be done with flow cytometry, but an imaging approach is relatively easier. Jung explains, “One of our customers is using the bacterial cell counter for quality control while manufacturing a cholera vaccine.” In this case, formalin fixation prevents colony counting, as the bacteria do not grow on agar plates. Hence, says Jung, “a single-cell counter is very important for this type of application.”
Automation expansion
Automated-counting features can be applied to more types of cells than in the past.
“Automated cell counting is requested for a large variety of samples,” says Ralf Ketterlinus, product manager at Germany-based OLS OMNI Life Science. “Besides bacteria and yeast, solutions to study water organisms—such as algae, paramecia or amoebae—are requested.” He adds, “Generally, accurate, objective and statistically significant counting is mandatory.”
This technology also improves an expanding range of studies. One of the interesting uses of automated techniques is counting “primary cells obtained from mouse models, typically including multiple tissue sites and multiple animals,” says Jean Qiu, chief technology officer and founder of Nexcelom Bioscience. “These samples contain heterogeneous cell types and debris from digestion.” As a result, such samples display very large variations in cell concentration and viability. Therefore, automated counts require very specific and accurate platforms.
Overall, the companies that make automated cell counters focus primarily on the obvious uses. “Traditional cell culture-related workflows are likely to always be the ‘bread and butter’ application for automated cell counting,” says Full. However, he adds that “adjacent markets and their corresponding niche applications—such as brewing science, biofuels and remote field-based research—will certainly be quite interesting to explore.”
Although automated cell counting provides ease, it can be expensive. “Researchers need to pay an additional cost for disposable counting slides,” Jung says.
Counting for more than a number
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Knowing the size of a cell population can impact the results obtained from assays applied to it. For example, normalizing data from cell-based assays can get a bit more complicated when the cell density in the volume being analyzed impacts the analytical signal being measured. In such cases, scientists need a measurement of the cell density. “This can be performed by measuring total DNA or protein, but most scientists prefer a direct measurement of cell number in the labware used to conduct the assay, such as a microplate—typically 96- or 384-well densities,” says Peter Banks, scientific director at BioTek Instruments. “Recently, BioTek collaborated with Agilent to normalize cellular metabolism data using [Agilent’s] Seahorse Biosciences technology.” Here, BioTek’s Cytation 5 Cell Imaging Multi-Mode Reader counts the cells in each well of Agilent’s Seahorse microplates, and the results can be used to normalize data on basal oxygen consumption rates and extracellular acidification rates. “This allowed us to normalize the data even for rapidly proliferating cell lines,” Banks adds.
Other twists on automated cell counting give scientists more options for analysis.
The CASY technology, for example, enables researchers to use electrical signals to count cells. In this technology, cells move through pores in the device, and as they block the opening, an electrical resistance is created that can be measured relative to the front and the back of the material containing the pore. Moreover, the membrane potential of live cells creates a higher resistance, so that live and dead cells can be distinguished.
Consequently, “CASY provides viability and size-distribution data of the cultures,” notes Ketterlinus. “The latter might well indicate genetic drifts in the biomass.” Brewers and manufacturers of yeast can use this for quality control of cultures.
Other experts also mention the use of automated cell counting in research or manufacturing that requires fermenting a sample. For instance, Qiu says, beer makers “count yeast and measure yeast viability and vitality to monitor the fermentation process during beer production for production quality and [to] produce consistency.”
Clinical scientists use primary and induced pluripotent stem (iPS) cells in an increasing number of ways, such as the development of cells to treat nervous-system damage or in the repair of various organs systems. “Here, researchers working with primary cells and iPS … cells appreciate the quality control of their cultures with regard to high-precision counting, size distribution, viability and state of aggregation, simply by a 10-second, cost-effective cell-counting procedure,” Ketterlinus says, “Statistically significant data, comparability of results and avoiding variance from manual counting are the key.”
This technology also enhances research on immunology. For instance, a team of scientists from Germany used CASY to examine the proliferation and metabolism of human T cells [1]. Their work revealed that altering some cellular processes, such as restricting mitochondrial activity, can reduce the proliferation of T cells but not affect their performance.
“In a nutshell, it’s not only the counts that count,” Ketterlinus concludes. Of course, when applying automated cell counting, scientists demand accurate and objective counts, but they want more, including information on cell viability, cell size, how cells aggregate and other metrics. As Ketterlinus says, scientists “require a comprehensive picture of their most important and sensitive research object, the cell.”
Reference
[1] Renner, K, et al., “Metabolic plasticity of human T cells: Preserved cytokine production under glucose deprivation or mitochondrial restriction, but 2-deoxy-glucose affects effector functions,” Eur J Immunol, 45:2504-16, 2015. [PMID: 26114249]