[mass noun] A synthetic blue dye used chiefly as a stain in biology.
- ‘The matrix or ground substance of cartilage is strongly basophilic and stains metachromatically with toluidine blue and other similar basic dyes.’
- ‘Specimens were stained with toluidine blue and basic fuchsin.’
- ‘Thick sections were stained with alkaline toluidine blue for light microscopic examination and selection of areas for electron microscopic study.’
- ‘The cytoplasm of medullar cells stains deeply with toluidine blue, while the cytoplasm of cortical cells stains faintly.’
- ‘Inactive DNA is readily stained with hematoxylin, toluidine blue, and other similar basic dyes.’
Late 19th century: toluidine from toluene + -ide + -ine.