Used in fluorescence imaging for biological research due to its strong near-infrared emission, enabling deep tissue visualization with low background autofluorescence. Commonly conjugated to antibodies, peptides, or nucleic acids for labeling specific cellular targets in live or fixed cells. Suitable for flow cytometry, confocal microscopy, and in vivo imaging. Water-soluble sulfonate groups enhance solubility and reduce nonspecific binding, improving signal clarity. Stable under standard labeling conditions and compatible with common biological buffers.