page_title: Trypan blue
section_title: Uses of trypan blue
hierarchical_section_title: Trypan blue / Uses of trypan blue
caption_attribution_description: X 400 English: Hyphea of Hyaloperonospora parasitica (downy mildew) growing within the leaf of a compatible (susceptible) Arabidopsis thaliana (cf.wikipedia) observed by bright-field microscopy. The staining with trypan blue makes the cytoplasm of H. parasitica dark blue. The long structure is the hyphea, whereas the little spheres are haustoria. Bigger dark spheres are Oospores, the long term storage form of H. parasitica. This is the mating step of the short life cycle of H. parasitica. Français&#160;: Hyphes de Hyaloperonospora parasitica (Mildiou) dans une feuille d'Arabidopsis thaliana (cf.wikipedia) susceptible (compatible) observée au microscope optique. La coloration au bleu de trypan donne une couleur bleue foncée au cytoplasme de H. parasitica. La longue structure est l'hyphe, tandis que les petites sphères sont les haustoria. Les sphères plus grosses et très sombres sont les Oospores, la forme de stockage à long terme de H. parasitica. C'est l'étape reproductive du cycle court de H. parasitica.
context_page_description: Trypan blue is an azo dye. It is a direct dye for cotton textiles. In biosciences, it is used as a vital stain to selectively colour dead tissues or cells blue.
  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 appear 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.
context_section_description: 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 may be used to observe fungal hyphae and stramenopiles.
  Trypan blue is also used in ophthalmic cataract surgery to stain the anterior capsule in the presence of a mature cataract, to aid in visualization, before creating the continuous curvilinear capsulorhexis. In keratoplasty, trypan blue can be used to stain the posterior stromal fibers during deep lamellar endothelial keratoplasty (DLEK) and to stain the endothelium in Descemet’s stripping endothelial keratoplasty (DSEK). Trypan blue is used in vitreoretinal surgeries also. 
  In early 20th century, the existence of a barrier protective toward the brain (blood brain barrier) was inferred, based on the observation that injection of trypan blue in animals led to whole‐body staining except for the brain and spinal cord.
caption: Observation with an optical microscope of Hyaloperonospora parasitica within a leaf of Arabidopsis thaliana by using the trypan blue staining.
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