Stains biological

Because, in the main, they show little contrast with their surroundings, biological materials are very difficult to visualise under a light microscope. Consequently, for many years in histology, visualisation of biological tissues has been assisted by coloration with dyes. These dyes, known as stains, can perform several functions  

Almost every class of dye has been used for histological staining and there is extensive literamre on the topic A simple classification of the dyes is as follows  

Representative stains in each of these chemical classes and some of their applications are shown in Table 2.9. ° 

Acid-fast bacteria, acid-fast bacilli and as rickettsia stain/Cain s method for mitochondria NEtj For staining Negri bodies in nerve cells 

Stain for connective tissue and erthrocytes For proteinaceous material in liver Cain s method for mitochondria 

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One of the main uses of osmium tetroxide is as a biological staining agent for microscopic ceU and tissue studies. Osmium tetroxide is unique in that it both fixes and stains biological material. 

This mixture is known as Quinoline Yellow A [8003-22-3] (Cl 47000) and is most widely used with polyester fibers (109). Upon sulfonation, the water-soluble Quinoline Yellow S or Acid Yellow 3 [8004-92-0] (Cl 47005) is obtained. This dye is used with wool and its aluminum salt as a pigment. Foron Yellow SE-3GL (Cl Disperse Yellow 64) is the 3-hydroxy-4-bromo derivative. Several other quinoline dyes are commercially available and find apphcations as biological stains and analytical reagents (110). 

Azine dyes are relatively unimportant as a class of dyes but are used extensively as biological stains. Colors are mostly yellow to red. DurabiUty of some of these dyes is supported by the 1990 LATCC Buyers Guide pubflshed by the American Association of Textile Chemists and Colorists, which fists Basic Red 2, Safranine T [477-73-6] (13) and Basic Red 5, Neutral Red [553-24-2] (14), discovered in 1859 and 1879, respectively (1). Basic Red 2 is a safranine similar to mauveine (7). 

Eosin [15086-94-9] (tetrabromofluorescein), C2QHgBi40, made by the bromination of fluorescein, is both a dye and an adsorption indicator. Eosin Y /7 7372-87-17, C2QH Br40 2Na, the disodium salt, is a biological stain. 475 -Dibromofluorescein [596-03-2], C2QH2QBr20, is used in D C Orange No. 

The cyanine class of dyes is also useful in biological, medical, laser, and electro-optic appHcations. Dyes marketed as Povan [3546-41-6] (5) and Dithiazanine [7187-55-5] (6) are useful anthelmintics, and Indocyanine Green [3599-32-4] (7) is an infrared-absorbing tracer for blood-dilution medical diagnoses. "Stains-AU." is a weU-studied biological stain (8) and Merocyanine 540 s photochemotherapeutic activity is known in some detail (9). Many commercially available red and infrared laser dyes are cyanines (10). 

Dyes derived from these fundamental basic and acidic terminal groups are in current use today as photographic spectral sensiti2ers [100471-81 -6] (10), chemotherapeutic dyes [54444-00-7] (11), laser dyes [53655-17-7] (12), and biological stains [7423-31-6] (13) (Fig. 4). 

FBAs are used to brighten not only textile materials but also paper, leather and plastics. They are important constituents of household detergent formulations. More specialised areas of application include lasers, liquid crystals and biological stains. By far the most important uses for FBAs, however, are in applications to textiles and paper. Much of what follows will be concerned with these two categories. 

Taylor CR. Quality assurance and standardization in immunohistochemistry. A proposal for the annual meeting of the Biological Stain Commission. Biotech. Histochem. 1992 67 110-117. 

Used industrially as an oxidizing agent especially in conversion of olefins to glycols, and in the preparation of chlorates, peroxides, and periodates as a biological stain for adipose... 

Horubin RW. Understanding Histochemistry Selection, Evaluation and Design of Biological Stains, Hopwood, Chichester, UK, 1988. 

Congo red org chem C32H22N5Na205S2 An azo dye, sodium diphenyldiazo-bis-a-naphthylamine sulfonate, used as a biological stain and as an acid-base indicator it is red in alkaline solution and blue in acid solution. kag-go red ... 

Victoria blue orgchem CssHsiNs-HCI Bronze crystals, soluble in hot water, alcohol, and ether used as a dye for silk, wool, and cotton, as a biological stain, and to make pigment toners. vik tor-e-o blii ... 

Osmium (VIII) tetraoxide (Os + 40 —> OsO ) is a yellow crystal and probably the most important compound used as an oxidizing agent, as a biological stain in microscopy, and to detect fingerprints. 

Table 2.9 Selected biological stains and their applications...

Rose Bengal 525,540 (7.28 x 10 ) Biological stain, eye drops to assess... 

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