Aniline blue (Masson C) is a dye used in the Masson trichrome staining protocol, a histological staining procedure for visualizing collagen fibers, muscle tissue, and cell nuclei in tissue sections. Masson trichrome staining consists of three main stains: Hematoxylin, Biebrich scarlet, and aniline blue.
Aniline blue (Masson C) is specifically responsible for staining collagen fibers, giving them a blue-green color. The dye binds to collagen fibers via acidic cellular components such as mucopolysaccharides. In combination with the other dyes, Masson trichrome staining provides a differentiated visualization of cell and tissue structures, allowing detailed examination under the microscope and identification of different cell types and morphological changes. This staining technique is frequently used in histopathological diagnostics and in the examination of connective tissue changes.