Which technique uses copper phthalocyanine as a chromagen to stain tissue?

• A. Luxol Fast Blue
• B. Hematoxylin and Eosin
• C. Ziehl-Neelsen
• D. Oil Red O

Answer: (A)

Staining with copper phthalocyanine is used in Luxol Fast Blue to color myelin blue in nervous tissue. This dye is lipid-friendly and binds specifically to the myelin heritable lipids, making the white matter stand out against other tissue components. In practice, Luxol Fast Blue is often paired with a counterstain (like cresyl violet) to also visualize neuronal cell bodies, which helps distinguish different structures in CNS tissue. The copper phthalocyanine component gives the distinctive blue color that identifies myelinated fibers.

The other stains work with different chromogens: one uses a hematoxylin-eosin combo for general tissue morphology, another uses carbol fuchsin for acid-fast organisms, and another stains lipids red in frozen sections without copper phthalocyanine.