Cell Counting-Viability
The most common method for assessing cell viability and counts is a decades-old methodology — trypan blue exclusion — that requires manual cell counting using the embedded grid of a hemacytometer. This method is less than ideal.
The variabilities involved with manual counting aside, trypan blue-based counting requires the scientist to “master” the art of interpreting and classifying particles based on size and overall blueness, which is anything but objective. Interpreting the inevitable multiple shades of blue across a stained sample is truly subjective, generally delivering imprecise and inconsistent cell counts. Not surprisingly, trypan blue chemistry has been reported in the literature to consistently overestimate cell viability[REF].
Another method to assess cell viability includes a fluorescence-based approach that monitors propidium iodide (PI) exclusion from living cells. This exclusion assay uses a fluorescent signal to distinguish healthy cells form those with compromised membrane integrity. PI exclusion examined by flow cytometry can distinguish a cell subpopulation stained with intermediate levels of PI. However, routine flow cytometry approaches do not allow for absolute cell counts without using reference beads, which adds cost and complexity to the assay.
The Guava ViaCount® Cell Counting & Viability Assay, when used in conjunction with a Guava® System, offers an automated, easier, and more accurate alternative to trypan blue, PI, and traditional flow cytometry approaches for cell counting. Based on a combination of two fluorescent nucleic acid dyes, the automated ViaCount Assay identifies cells while excluding debris, and distinguishing live from dead and apoptotic cells. Assay results include total cell count, and cell counts and percentages for both viable and apoptotic cells.
For more information about how a Guava System can meet your cell counting needs, please visit the following links.
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