Safranine

Safranine, commonly known as safranin, is a reddish basic dye used in microscopy and histology. It belongs to the phenazinium family of dyes and is typically applied in the form of water- or alcohol-soluble salts, with safranin O being the most widely used variant. The dye carries a positive charge, which helps it bind to negatively charged cellular components such as nucleic acids and certain tissue constituents.

In microbiology, safranin is best known as a counterstain in the Gram staining protocol. After the decolorization step, Gram-negative bacteria take up the red color from safranin, while Gram-positive bacteria retain the purple color from crystal violet. Safranin is also used in some spore staining procedures as a secondary stain to color vegetative cells red.

In histology and botany, safranin is used to stain lignified plant tissues, mucins, and cartilage matrix, producing a red to pink color. When used in combination with a counterstain such as fast green, it helps differentiate tissue components by color contrast, for example highlighting lignified cell walls in plant sections.

Variants and preparation notes: Safranine is available as aqueous or alcoholic solutions, often labeled as safranin O. The shade and performance can vary with pH and fixing conditions; different derivatives may yield slightly different hues. The term “safranin” is sometimes used broadly to refer to related red dyes in the same chemical family.

Safety: Safranine is a chemical dye and can be an irritant to skin and eyes. Proper laboratory precautions, including gloves and eye protection, should be used, and waste disposed of according to applicable regulations.