Eosin

Eosin is a fluorescent red dye resulting from the action of bromine on fluorescein. It can be used in staining animal tissues, in microscopy, and as a tracking dye for nucleic acids in electrophoresis.

History

Eosin was first synthesized in 1871 by the German chemist Heinrich Caro. The name "eosin" derives from Eos, the Ancient Greek word for 'dawn' and the name of the Greek goddess of the dawn.

Chemical Properties

Eosin is usually found as a disodium salt. The bromine can be replaced by other halogens (iodine, chlorine, fluorine), giving eosin derivatives that are essentially the same in applications. In aqueous solution eosin Y is yellowish, appearing red when in a concentrated solution.

Uses

Eosin is most often used as a stain in histology and cytology. It stains cytoplasm, collagen and muscle fibers pink or red. It can also be used to stain the cytoplasm of cells in samples, such as biopsies or cell smears. It is often used in combination with other dyes, such as hematoxylin in H&E staining.

Health Effects

Exposure to eosin can cause eye, skin, and respiratory tract irritation. It may also cause allergic skin reactions.

See Also

• Histology
• Cytology
• H&E staining
• Heinrich Caro

References

Eosin Resources
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