Safranin

Safranin is a biological stain used in histology and cytology. It is a cationic (positively charged) dye that stains acidic or negatively charged structures, making them visible under a microscope.

Properties and Uses:

Safranin typically appears as a red-colored powder and is often used in solution. Its primary use is as a counterstain in Gram staining, a differential staining technique used to distinguish between different types of bacteria. In Gram staining, safranin stains Gram-negative bacteria pink or red after the primary stain (crystal violet) and mordant (Gram's iodine) have been washed away and the cells decolorized with alcohol or acetone. Gram-positive bacteria, which retain the crystal violet, appear purple or blue.

Beyond Gram staining, safranin is used in other staining procedures to highlight cell nuclei and other structures, such as cartilage and collagen. It is also employed in some botanical staining protocols to stain lignified cell walls in plant tissues, often in combination with fast green or other stains.

Mechanism of Action:

As a cationic dye, safranin binds to anionic (negatively charged) components within cells and tissues. These components often include nucleic acids (DNA and RNA) and acidic polysaccharides. The strength of the staining depends on factors such as the concentration of the dye, the staining time, the pH of the solution, and the characteristics of the tissue being stained.

Safety Considerations:

While generally considered relatively safe when handled properly in a laboratory setting, safranin can cause irritation to the skin, eyes, and respiratory tract. Appropriate personal protective equipment, such as gloves, eye protection, and a lab coat, should always be worn when working with safranin. Material Safety Data Sheets (MSDS) should be consulted for detailed safety information.

Chemical Structure:

Safranin is a complex organic molecule belonging to the azine dye family. It is structurally related to phenazine and is typically available as a salt, such as safranin O.

Synonyms:

• Basic Red 2
• C.I. Basic Red 2