I did my PhD in the Department of Chemical Engineering at Imperial College London. My research focused on mathematical modeling of the cell cycle in leukemia and involved experiments with cell lines. During that time, I had to count cells with a hemocytometer so often to track growth that I got tired and decided to build an app, HemocyTap, and share my knowledge on the topic here to help as many people as possible.

Looking for a live/dead assay, and not sure which one is best? Here we have the answer for you.

Why do a live/dead assay?

You should regularly track the viability of your cell culture, as it is representative of how healthy it is. The way you do this is by counting live and dead cells using a hemocytometer, and adding a dye that will selectively penetrate inside the dead (or apoptotic) cells, whose cellular membrane is damaged, while live cells will stay unstained. It’s really a simple method, and if you are counting cells with a hemocytometer anyway it’s worth to throw in a viability dye and count both populations (after all, most of us have two hands right? So don’t be stupid, count live with one counter and dead with the other one!).

What are the most commonly used dyes?

All viability dyes to be used together with a hemocytometer have the property of penetrating damaged cell membranes. The two most common are trypan blue and erythrosine B. Trypan blue is a blue (…) dye chemically derived from toluene. Erythrosin B is a cherry pink dye composed of a fluorescein salt (i.e. sensitive to light at certain wavelengths).

The duel: trypan blue vs. erythrosine B

Unsure about which one fits your needs best? Have a look below.
Trypan blue Erythrosine B
Stains what? Dead cells + serum proteins Dead cells only
How much do I add?* >400μg/mL >5μg/mL
Time needed since cell death* >50min 1min
In case you’re into fashion, what color? blue pink
In case you drop some, how bad is it? Toxic (known carcinogenic) It’s a food additive, what do you think? Bad for your clothes, maybe.
For cell lovers: how bad is it for the cells? Toxic Non toxic for periods of over 2h

Overall, erythrosin B is a more reliable, less toxic method both for you and for the cells.


    1. Hi Isha,

      Quick answer: yes. Explanation: The debris are just cell fragments of dead cells. When they die, cells membranes become permeable to the liquid around them (be it water, PBS or a colored dye). If they are further lysed (degraded), the dead cell breaks and releases its cellular contents. This is what you call cellular debris, and since they already had lost their membrane capacity to isolate them form their environment when they were dead, they do uptake trypan blue, or any other dye. See for example here, the sample contains cells that have been exposed to chemotherapy so they are all dead (stained blue), and you can see a lot of blue particles in the background as well, which are the cell debris.

      Hope that helped!


  1. Hello,

    I have a question. When we used the Erythosine-B what happend with the cells that may be are in cell cycle arrest? are alive, so I showld see them unstained?

    1. Hi Laura,
      If they are in cell cycle arrest, they should not be stained. If they become apoptotic (which can happen if you leave them in cell cycle arrest for a long time), they can become stained.
      Hope that helps!

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