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| Names | |
|---|---|
| IUPAC name (7-amino-8-methylphenothiazin-3-ylidene)-dimethylammonium chloride | |
| Other names Toluidine blue O | |
| Identifiers | |
| |
3D model (JSmol) | |
| ChEBI | |
| ChEMBL | |
| ChemSpider |
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| ECHA InfoCard | 100.001.952 |
| MeSH | Tolonium+chloride |
| UNII | |
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| |
| Properties | |
| C15H16N3S+ | |
| Molar mass | 270.374 g/mol |
Except where otherwise noted, data are given for materials in theirstandard state (at 25 °C [77 °F], 100 kPa). | |
Toluidine blue, also known asTBO ortolonium chloride (INN) is a blue cationic (basic) dye used inhistology (as thetoluidine blue stain) and sometimes clinically.
Toluidine bluesolution is used in testing forlignin, a complexorganic molecule that bonds tocellulose fibres and strengthens and hardens thecell walls inplants. A positive toluidine blue test causes thesolution to turn from blue to blue-green.[1] A similar test can be performed withphloroglucinol-HCl solution, which turns red.
Toluidine blue is a basicthiazinemetachromatic dye with high affinity for acidic tissue components.[2] It stains nucleic acids blue and polysaccharides purple and also increases the sharpness of histology slide images. It is especially useful today for stainingchromosomes in plant or animal tissues, as a replacement forAceto-orcein stain.
Toluidine blue is often used to identifymast cells, by virtue of theheparin in theircytoplasmic granules.[3] It is also used to stainproteoglycans andglycosaminoglycans in tissues such as cartilage. The strongly acidic macromolecular carbohydrates of mast cells and cartilage are coloured red by the blue dye, a phenomenon calledmetachromasia.
Alkaline solutions of toluidine blue are commonly used for staining semi-thin (0.5 to 1 μm) sections of resin-embedded tissue. At high pH (about 10) the dye binds to nucleic acids and all proteins. Although everything in the tissue is stained, structural details are clearly visible because of the thinness of the sections. Semi-thin sections are used in conjunction with ultra-thin sections examined byelectron microscopy.
Toluidine blue is also commonly used to stain frozen sections (rapid microscopic analysis of a specimen). Because time is of the essence for a frozen section, toluidine blue allows for the frozen section to be stained and reviewed in 10 to 20 seconds.[4] The other staining method for frozen sections (rapid H&E) takes approximately 60 to 90 seconds.
The results depend on the studied organs:[5]
It is used in forensic examination,[6]renalpathology[7] andneuropathology.
The dye is sometimes used by surgeons to help highlight areas ofmucosaldysplasia (which preferentially take up the dye compared to normal tissue) inpremalignantlesions (e.g.leukoplakia).[8] This can be used to choose the best site of the lesion tobiopsy, or during surgery to remove the lesion to decide whether to remove more tissue from the margins of the excision defect or leave it behind.
