Trypan Blue 0.4% Solution

Trypan Blue is a stain used to distinguish viable from nonviable cells. Nonviable cells absorb the dye and appear blue, while viable cells exclude the dye. Cells should be in a single cell suspension in buffered saline before counting. Since trypan blue has a higher affinity for serum proteins than for cellular proteins, suspending the cells in medium containing serum will generate a dark background.