You only want to know how many viable cells (% viability) you have? If the answer is yes, yes you can do flow or any technique to check viability, MTT, WST, or trypan. The people do trypan because is quick, cheap and easy, not requires expensive equipments, etc. If you want to do flow because you have huge quantity of samples to analyze (is the only reason I could select flow vs trypan for this purpose) you can do it, but not stain with trypan, you could use DAPI as common live/dead stainning (you could do more refine protocols such as PI if you are going to do flow if you want).

Moreover, you said you are going to freeze in PBS. I not understand this step, if you freeze in PBS, you are not going to have viable cells anymore, you have to freeze in FBS + DMSO (or medium + DMSO). If you want to freeze to extract nucleic acids or protein you have other better options than PBS.

Miguel Gallardo you are absolutely right about the freezing medium (we use exactly what you mentioned). External lab has told us, that they can count % of viable cells using FLOW. Just needed to be sure if it's possible.

p.s. could you please tell me more about this --> "If you want to freeze to extract nucleic acids or protein you have other better options than PBS. "

Thank you!

Hi Kakhaber,

I normally use trypan blue to evaluate viability, but in some cases I used FACS to determine the percentage of live cells. In general, you can buy several dyes with also different conjugations. I personally used 7-AAD and it works very well:

https://www.bdbiosciences.com/us/applications/research/apoptosis/buffers-and-ancillary-products/7-aad/p/559925

But for FACS there are even ready-to-use fixable dyes:

https://www.thermofisher.com/ch/en/home/life-science/cell-analysis/flow-cytometry/flow-cytometry-assays-reagents/cell-viability-assays-flow-cytometry/fixable-viability-dyes-flow-cytometry.html

or non-fixable dyes:

https://www.thermofisher.com/ch/en/home/life-science/cell-analysis/flow-cytometry/flow-cytometry-assays-reagents/cell-viability-assays-flow-cytometry/nonfixable-viability-dyes-flow-cytometry.html

I also used the LIVE/DEAD Fixable Dead Cell Stain Kit and I am satisfied with the result.

Cheers