In recent years, automated cell counting has become an attractive alternative to manual hemocytometer-based cell counting because it offers more reliable results in a fraction of the time needed for manual counting; it also significantly reduces user- and concentration-dependent count variance. A recent comparison of automated and manual cell counting methods showed improved count reproducibility and accuracy and reduced time to results.
Automated cell counters can be based on image analysis, flow (flow cytometers), or electrical impedance (Coulter counters). When used with dye image-based cell counters, flow cytometers can determine not only the number of cells in the sample but also how many are viable; most Coulter counters can determine only the number of cells in the sample. Automated cell counters like the TC20™ automated cell counter can provide both total cell counts and the percentages of viable and dead cells.
Find cell viability, cytotoxicity, and hemocytometer counting protocols in the Related Content section below.
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Image-based cell counters such as Bio-Rad's TC20 automated cell counter utilize bright-field or fluorescent microscopes coupled with digital cameras (CMOS or CCD) to obtain images that are then analyzed with image analysis software. These automated cell counters are either self-contained (internal PC) or connected to an external computer.
The sample is contained in a disposable consumable (slide, or cartridge) that ensures the same volume is analyzed each time, allowing for accurate volumetric counts. The consumable is an integral part of the counting system and its performance impacts accuracy of the results. The patent-pending design of the TC20 counting slides ensures even sample distribution regardless of a user's pipetting style, leading to accurate and reproducible results.
Visit the TC20 cell counter product page for more information including instructional videos, tech notes, and more.
Bright-field-based cell counters use colorimetric dyes (for example, Trypan blue) for cell viability analysis, whereas fluorescent cell counters use fluorescent dyes for viability analysis.
See how the TC20 cell counter uses multiple focal plane analysis to assess cell viability, which prevents inaccurate counts that result from light scattering and alignment of cells at different heights in the counting chamber when analyzing viability on only a single focal plane.
Flow cytometers are used to measure the characteristics of individual cells and particles that are delivered in a flow system past a point of measurement where light is focused on one cell or one particle at a time. Then, the scattered light and fluorescent signals of different wavelengths are recorded.
Cell counting is one of many features available on these instruments; because they are complex to use, these instruments are usually not purchased solely for cell counting. Some flow cytometers use accurate volumetric pumps and are able to provide volumetric counts. To get absolute counts using cytometers that do not use the volumetric pumps, users have to introduce a calibrated means (usually beads) to determine the volumetric count.
Coulter counters are particle counters based on electrical impedance. As the liquid containing cells or other objects is drawn through a small aperture, it causes a change in electrical impedance proportional to the size of the particles. Coulter counters provide the number and size of cells per particle within the sample. However, Coulter counters are unable to provide cell viability information.
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