What is the number of primary cells per vial frozen at PromoCell? How can I calculate the number of viable cells and how should I calculate the optimal plating density?

At PromoCell we guarantee for our primary human cells ≥ 500,000 viable cells after thawing. For this, we dispense > 500,000 cells per cryovial before cryopreservation as there will always be a certain percentage of dead cells after freeze/thaw. In order to know the number of cells that survived the procedure, we defrost a representative number of vials per lot during QC, determine the cell viability using an electronic counting device and then calculate the number of viable cells that can be recovered after thawing. Both numbers - the calculated number of viable cells and the viability - can be found on the lot-specific Certificate of Analysis (CoA) that can be downloaded from our website. Example: When the CoA indicates 600,000 viable cells and a viability of 80%, this means that the vial actually contains 750,000 cells (viable + dead), 80% thereof (600,000) were viable after thawing in our QC. We do not indicate the total number of cells per vial but just the number of expected viable cells which can be recovered when the recommended thawing protocol is used. You don't have to calculate any viabilities by yourself. When the recommended plating density for your cell type is 5,000 - 10,000 cells/cm², then the 600,000 viable cells can be plated e.g. in a T75 (corresponding to 8,000 cells/cm²) or in a T75 + a T25 (corresponding to 6,000 cells/cm²).