Trypan blue
Trypan blue is a vital stain used to selectively colour dead tissues or cells blue. It is a diazo dye.
Live cells or tissues with intact cell membranes are not coloured. 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 colour under a microscope. Since live cells are excluded from staining, this staining method is also described as a dye exclusion method. This dye may be a cause of certain birth defects such as encephalocele.
Background & chemistry
Trypan blue is derived from toluidine, that is, any of several isomeric bases, C14H16N2, derived from toluene. Trypan blue is so-called because it can kill trypanosomes, the parasites that cause sleeping sickness. An analog of trypan blue, suramin is used pharmacologically against trypanosomiasis. Trypan blue is also known as diamine blue and Niagara blue.
The extinction coefficient for trypan blue is 6 x 104 M−1 cm−1 at 607nm in methanol.
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