Toluidine blue 2% aqueous solution is a versatile stain used in histology and cytology. Its ability to selectively stain various cell structures such as mast cells, cartilage tissue, and acidic mucopolysaccharides should be emphasized.

A special feature of toluidine blue staining is metachromasia, in which the stain changes color depending on the binding affinity to the cell structures. This effect is due to the interaction between the cationic toluidine blue and the anionic groups of the acidic mucopolysaccharides.

Toluidine blue binds to the acidic groups of the mucopolysaccharides, leading to a stacking of the dye molecules, which causes a change in the absorption spectra. As a result, the acidic mucopolysaccharides appear metachromatic in purple hues, although the original color of toluidine blue.

In addition to metachromasia, orthochromatic staining of mast cells and cartilage tissue provides differentiated visualizations. Mast cells are stained in red hues, while cartilage tissue appears blue. In doing so, toluidine blue binds to the respective cell structures without undergoing a color change.

Compared to other staining agents, the aqueous toluidine blue 2% solution is characterized by its ease of use and precise visualization of different cell structures. These properties enable efficient and accurate analysis of tissue samples and contribute to the quality of histological and cytological examinations.