Used as a fluorescent dye in biological imaging and staining applications. Its strong fluorescence and water solubility make it suitable for labeling biomolecules such as proteins and nucleic acids. Commonly employed in flow cytometry, fluorescence microscopy, and immunoassays due to its high photostability and bright emission in the near-infrared range. The sulfonate and carboxylate groups allow for conjugation with amine-containing molecules using standard coupling chemistry. Also used in diagnostic kits and cellular tracking studies where deep tissue penetration and low background interference are required.