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Home / Techniques / Protocols / Toluidine blue

Techniques. Protocols

TOLUIDINE BLUE

Toluidine blue (C.I. 52040) is a cationic dye used in general staining procedures. It stains the extracellular matrix, mostly cartilage, because it labels glycosominoglycans and proteoglycans. It is also useful to observe osteblasts, taste buds and chromosomes. Furthermore, it shows metachromasia, which is useful in plant tissues to distinguish primary cell walls from secondary cells walls. Molecularly, toluidine blue is a thiazine dye.

Procedure

0,5 g toulidine blue (C.I. 52040)

1 ml glacial acetic acid

99 ml distilled water or acetate buffer pH 4

Notes

The optimal pH is about 3 - 5,5, depending on the fixative and type of tissue. The staining time is about 3 min The dehydration has to be fast. Otherwise, the staining is faded out. That is why dehydration starts with 95 º ethanol.

The fading of the staining during dehydration can be prevented by incubation in 5 % ammonium molibdate in distilled water for 5 min. Thus, dehydration can be performed without loosing color.

Most structures, such as nuclei and carbohydrates, are stained in blue, but other colors may appear due to metachromasia.

Products

Toluidine blue (C.I. 52040)

Glacial acetic aci

Acetate buffer

Distilled water

Labware

Test tube

Balance

Magnetic stirrer

pH meter

Flasks

Bottles

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