Toluidine blue, also known as TBO or tolonium chloride ( INN) is a blue cationic (basic) dye used in

histology Histology, also known as microscopic anatomy or microanatomy, is the branch of biology that studies the microscopic anatomy of biological tissue (biology), tissues. Histology is the microscopic counterpart to gross anatomy, which looks at large ...

(as the toluidine blue stain) and sometimes clinically.

Test for lignin

Toluidine blue

solution Solution may refer to: * Solution (chemistry), a mixture where one substance is dissolved in another * Solution (equation), in mathematics ** Numerical solution, in numerical analysis, approximate solutions within specified error bounds * Solu ...

is used in testing for

lignin Lignin is a class of complex organic polymers that form key structural materials in the support tissues of most plants. Lignins are particularly important in the formation of cell walls, especially in wood and bark, because they lend rigidit ...

, a complex

organic molecule Some chemical authorities define an organic compound as a chemical compound that contains a carbon–hydrogen or carbon–carbon bond; others consider an organic compound to be any chemical compound that contains carbon. For example, carbon-cont ...

that bonds to

cellulose Cellulose is an organic compound with the chemical formula, formula , a polysaccharide consisting of a linear chain of several hundred to many thousands of glycosidic bond, β(1→4) linked glucose, D-glucose units. Cellulose is an important s ...

fibres and strengthens and hardens the

cell wall A cell wall is a structural layer that surrounds some Cell type, cell types, found immediately outside the cell membrane. It can be tough, flexible, and sometimes rigid. Primarily, it provides the cell with structural support, shape, protection, ...

s in

plant Plants are the eukaryotes that form the Kingdom (biology), kingdom Plantae; they are predominantly Photosynthesis, photosynthetic. This means that they obtain their energy from sunlight, using chloroplasts derived from endosymbiosis with c ...

s. A positive toluidine blue test causes the

to turn from blue to blue-green. A similar test can be performed with

phloroglucinol Phloroglucinol is an organic compound with the formula C6H3(OH)3. It is a colorless solid. It is used in the organic synthesis, synthesis of pharmaceuticals and explosives. Phloroglucinol is one of three isomeric benzenetriols. The other two isom ...

- HCl solution, which turns red.

Histological uses

Toluidine blue is a basic thiazine metachromatic dye with high affinity for acidic tissue components. It stains nucleic acids blue and polysaccharides purple and also increases the sharpness of histology slide images. It is especially useful today for staining

chromosome A chromosome is a package of DNA containing part or all of the genetic material of an organism. In most chromosomes, the very long thin DNA fibers are coated with nucleosome-forming packaging proteins; in eukaryotic cells, the most import ...

s in plant or animal tissues, as a replacement for Aceto-orcein stain. Toluidine blue is often used to identify

mast cell A mast cell (also known as a mastocyte or a labrocyte) is a resident cell of connective tissue that contains many granules rich in histamine and heparin. Specifically, it is a type of granulocyte derived from the myeloid stem cell that is a p ...

s, by virtue of the

heparin Heparin, also known as unfractionated heparin (UFH), is a medication and naturally occurring glycosaminoglycan. Heparin is a blood anticoagulant that increases the activity of antithrombin. It is used in the treatment of myocardial infarction, ...

in their cytoplasmic granules. It is also used to stain

proteoglycan Proteoglycans are proteins that are heavily glycosylated. The basic proteoglycan unit consists of a "core protein" with one or more covalently attached glycosaminoglycan (GAG) chain(s). The point of attachment is a serine (Ser) residue to w ...

s and

glycosaminoglycan Glycosaminoglycans (GAGs) or mucopolysaccharides are long, linear polysaccharides consisting of repeating disaccharide units (i.e. two-sugar units). The repeating two-sugar unit consists of a uronic sugar and an amino sugar, except in the case o ...

s 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 An electron microscope is a microscope that uses a beam of electrons as a source of illumination. It uses electron optics that are analogous to the glass lenses of an optical light microscope to control the electron beam, for instance focusing i ...

. 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. The other staining method for frozen sections (rapid H&E) takes approximately 60 to 90 seconds. The results depend on the studied organs: *Mastocytes in purple *Cartilage in purple *Mucins in purple/red *Nuclei in blue It is used in forensic examination,

renal In humans, the kidneys are two reddish-brown bean-shaped blood-filtering organs that are a multilobar, multipapillary form of mammalian kidneys, usually without signs of external lobulation. They are located on the left and right in the retrop ...

pathology Pathology is the study of disease. The word ''pathology'' also refers to the study of disease in general, incorporating a wide range of biology research fields and medical practices. However, when used in the context of modern medical treatme ...

and

neuropathology Neuropathology is the study of disease of nervous system tissue, usually in the form of either small surgical biopsies or whole-body autopsies. Neuropathologists usually work in a department of anatomic pathology, but work closely with the clini ...

Clinical uses

The dye is sometimes used by surgeons to help highlight areas of

mucosal A mucous membrane or mucosa is a membrane that lines various cavities in the body of an organism and covers the surface of internal organs. It consists of one or more layers of epithelial cells overlying a layer of loose connective tissue. It is ...

dysplasia Dysplasia is any of various types of abnormal growth or development of cells (microscopic scale) or organs (macroscopic scale), and the abnormal histology or anatomical structure(s) resulting from such growth. Dysplasias on a mainly microscopic ...

(which preferentially take up the dye compared to normal tissue) in premalignant

lesion A lesion is any damage or abnormal change in the tissue of an organism, usually caused by injury or diseases. The term ''Lesion'' is derived from the Latin meaning "injury". Lesions may occur in both plants and animals. Types There is no de ...

s (e.g.

leukoplakia Oral leukoplakia is a potentially malignant disorder affecting the oral mucosa. It is defined as "essentially an oral mucosal white/gray lesion that cannot be considered as any other definable lesion." Oral leukoplakia is a gray patch or plaque th ...

). This can be used to choose the best site of the lesion to

biopsy A biopsy is a medical test commonly performed by a surgeon, interventional radiologist, an interventional radiologist, or an interventional cardiology, interventional cardiologist. The process involves the extraction of sampling (medicine), sample ...

, 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. SMCpolyhydroxysmall

Test for lignin

Histological uses

Clinical uses

See also

References

Further reading