Trypan Blue, sodium salt *CAS 72-57-1*

Trypan blue, a diazo dye is a vital stain that colors dead tissues or cells blue. Live cells or tissues with intact cell membranes are not be colored. Since cells are very selective in the compounds that pass through the membrane, in a viable cell trypan blue is not absorbed; however, it traverses the membrane in a dead cell. Hence, dead cells are shown as a distinctive blue color under a microscope. Trypan blue is commonly used in microscopy (for cell counting) and in laboratory mice for assessment of tissue viability. The method cannot distinguish between necrotic and apoptotic cells. It is also useful to observe hyphea of fungi and Stramenopiles.