Viabilitetsfärgningar

Viabilitetsfärgningar, also known as viability stains, are dyes used in biology and medicine to distinguish between living and dead cells. These stains typically work by entering cells with damaged cell membranes, which are characteristic of dead or dying cells. Living cells, with intact membranes, exclude these dyes, thus appearing unstained or differently colored.

A common example of a viability stain is trypan blue. Trypan blue is a vital stain that cannot cross the membrane of a healthy cell. However, if a cell's membrane is compromised, as is the case with dead cells, the dye enters the cell and stains it blue. By observing a cell suspension under a microscope after adding trypan blue, researchers can easily count the unstained (live) cells and the stained (dead) cells to determine the viability of the cell population.

Other viability stains exist, each with slightly different properties and applications. Propidium iodide (PI) is another frequently used stain that intercalates into DNA and fluoresces red. Like trypan blue, PI cannot enter living cells but readily enters dead cells with damaged membranes, making it useful for flow cytometry and fluorescence microscopy. Acridine orange is a fluorescent dye that can stain both live and dead cells differently; live cells take up the dye and fluoresce green, while dead cells also take up the dye but fluoresce orange or red due to DNA degradation.

The use of viability stains is crucial in many research areas, including cell culture, drug screening, and diagnostics. Accurately assessing cell viability ensures the reliability of experimental results and helps in understanding cellular responses to various treatments or conditions.