Viable count is a method used in
cell culture
Cell culture or tissue culture is the process by which cells are grown under controlled conditions, generally outside of their natural environment. The term "tissue culture" was coined by American pathologist Montrose Thomas Burrows. This te ...
to determine the number of living cells in a culture. This is different from other
cell counting techniques because it makes a distinction between live and dead cells.
Method
A dilution of the cells to be counted is prepared and mixed with
Trypan blue
Trypan blue is an azo dye. It is a direct dye for cotton textiles. In biosciences, it is used as a vital stain to selectively colour dead tissues or cells blue.
Live cells or tissues with intact cell membranes are not coloured. Since cells a ...
, this is normally the stain of choice because it is taken up by dead cells and actively excluded from live cells. Once the cells have been stained they are counted using a
Hemocytometer
The hemocytometer (or haemocytometer) is a counting-chamber device originally designed and usually used for counting blood cells.
The hemocytometer was invented by Louis-Charles Malassez and consists of a thick glass microscope slide with a ...
, then a calculation is carried out to determine the original concentration of live cells.
Use in Cell Culture
Determining the viable cell count is important for calculating dilutions required for the
passaging
In biology, a subculture is either a new cell culture or a microbiological culture made by transferring some or all cell (biology), cells from a previous culture to fresh growth medium. This action is called subculturing or passaging the cells. Sub ...
of cells, as well as determining the size and number of flasks needed during growth time. It is also vital when seeding plates for assays, such as the
plaque assay
Virus quantification involves counting the number of viruses in a specific volume to determine the virus concentration. It is used in both research and development (R&D) in commercial and academic laboratories as well as production situations whe ...
,
because the plates need a known number of live replicating cells for the virus to attach to and replicate in, in order to get an accurate result.
References
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Cell culture