Cell Viability (membrane integrity) can be measured with the NucleoCounter® SP-100™ in a two-step procedure by measuring the difference between the total cell count and the non-viable cell count (see figure below).

When a sample is diluted with S100 Reagent, lysis of the viable cell membrane occurs, rendering all cell nuclei susceptible to propidium iodide (PI) staining, resulting in a total cell count.

However, nonviable cells diluted with PBS (phosphate buffered saline) are permeabilized without treatment and therefore stain directly with PI, resulting in a nonviable cell count. The difference between the two measurements gives the viable cell count – or % viability.