The Three-Step Stain Set is comprised of three components: a methanol fixative (Fixative), an aqueous eosin solution (Solution A), and an aqueous methylene blue/azure A solution (Solution B). The staining solutions consist of xanthene and thiazine dyes, exhibiting both anionic and cationic properties, respectively. Cationic cellular components, such as erythrocytes and eosinophilic granules, share an affinity for the anionic dye of Solution A. The negatively charged phosphate groups of DNA and basophilic granules of the cytoplasm have an affinity for the polychromatic cationic dyes of Solution B. The aqueous stain formulations function to dissociate and activate the dye ions, allowing them to chemically bond with specific cellular components. When staining blood and bone marrow smears, the pH of the staining solutions is a critical factor
A single chemical agent, dye or solution intended for the artificial colouration of specific target tissue structures, intra/extracellular elements and/or infectious microorganisms, in a clinical specimen, for their subsequent visualization, examination, identification and/or differentiation.