Which statement about Alcian blue is true?

• A. It is a copper-based basic dye that is water soluble and blue because of copper
• B. It is a fat-soluble anionic dye
• C. It stains lipids blue
• D. It is a red dye

Answer: (A)

Alcian blue is a copper-containing, basic dye used to stain acidic mucopolysaccharides (glycosaminoglycans) in tissue sections. Its pleasant blue color comes from the copper in the dye, and it stays water-soluble because of sulfonate groups that keep it in solution. The staining occurs through ionic attraction: the positively charged dye binds to the negatively charged acidic groups on mucins, sulfated and carboxylated glycosaminoglycans. This makes the statement describing Alcian blue as a copper-based basic dye that is water soluble and blue because of copper the correct one. It is not a fat-soluble lipid stain, nor a red dye, and it does not stain lipids blue.