Toluidine blue

Tolonium chloride

Names
IUPAC name (7-amino-8-methyl- phenothiazin-3-ylidene)- dimethyl-ammonium
Other names Toluidine blue O
Identifiers
CAS Number	92-31-9 N
3D model (Jmol)	Interactive image
ChEBI	CHEBI:87647 N
ChEMBL	ChEMBL1790006 N
ChemSpider	11239098 Y
ECHA InfoCard	100.001.952
MeSH	Tolonium+chloride
PubChem	7084
UNII	15XUH0X66N N
InChI InChI=1S/C15H16N3S.ClH/c1-9-6-13-15(8-11(9)16)19-14-7-10(18(2)3)4-5-12(14)17-13;/h4-8H,16H2,1-3H3;1H/q+1;/p-1 Y Key: HNONEKILPDHFOL-UHFFFAOYSA-M Y InChI=1/C15H16N3S.ClH/c1-9-6-13-15(8-11(9)16)19-14-7-10(18(2)3)4-5-12(14)17-13;/h4-8H,16H2,1-3H3;1H/q+1;/p-1 Key: HNONEKILPDHFOL-REWHXWOFAY
SMILES [Cl-].CN(C)c1ccc2nc3cc(C)c(N)cc3[s+]c2c1
Properties
Chemical formula	C15H16N3S+
Molar mass	270.374 g/mol
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
N  (what is YN ?)
Infobox references

Tolonium chloride (INN, also known as toluidine blue or TBO) is a blue cationic (basic) dye used in histology and sometimes clinically.

Toluidine blue solution is used in testing for lignin, a complex organic molecule that bonds to cellulose fibres and strengthens and hardens the cell walls in plants. A positive toluidine blue test causes the solution to turn from blue to pink. A similar test can be performed with phloroglucinol-HCl solution, which turns red.

Toluidine Blue is often used to identify mast cells, by virtue of the heparin in their cytoplasmic granules. It is also used to stain proteoglycans and glycosaminoglycans in tissues such as cartilage. The strongly acidic macromolecular carbohydrates of mast cells and cartilage are coloured red by the blue dye, a phenomenon called metachromasia.

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 by electron microscopy.

The dye is sometimes used by surgeons to help highlight areas of mucosal dysplasia (which preferentially take up the dye compared to normal tissue) in premalignant lesions (e.g. leukoplakia). This can be used to choose the best site of the lesion to biopsy, 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.