Toluidine blue is a basic (or acidophilic) staining based on the principle of metachromasia: due to molecular properties, the stain intensity varies in different tissue components depending on their pH, temperature and concentration variations. The components stained in purple or red are called metachromatic while the other components are orthochromatic because they keep the blue staining. The toluidine blue stain has a good affinity for molecules negatively charged like nucleic acids, cartilage and mucin mucopolysaccharides, heparin and histamine mastocyte granulations…
Toluidine blue staining is quick and easy to apply. It is therefore an alternative to Hematoxylin Eosin (HE) staining. It is particularly used by pathologists to observe the abnormal presence of mastocytes due to a cancer, an inflammatory or a gastrointestinal disease like irritable bowel syndrome. This staining is also used to highlight cartilage and mucins composed of mucopolysaccharides. Moreover, toluidine blue staining is an interesting method for the early diagnostic of cancer because DNA labeling in cancer cells is more intense than in healthy cells.
Toluidine blue staining is used on all kinds of tissues or organs.