Sulfo-Cy7.5 carboxylic acid is a dye derivative of Cyanine 7.5 (Cy7.5) with carboxylic acid and sulfonate ion (sulfonate) functional groups. The sulfonate ion increases the water solubility of the compound, making it suitable for use in aqueous solutions. Cy7.5 is a near-infrared fluorescent dye commonly used in biomedical research areas such as biomarkers and cell imaging. Sulfo-Cy7.5 carboxylic acid can be covalently bound to some biomolecules (especially antibodies , proteins, etc.) to track their location and dynamic changes in biological samples.