Sulfo-Cy5.5 ethylenediamine is widely used in biomedical research for fluorescence labeling and imaging applications. Its near-infrared emission makes it ideal for in vivo imaging, as it allows deep tissue penetration with minimal background interference. This dye is commonly conjugated to proteins, antibodies, or peptides to track cellular processes, study molecular interactions, and visualize biological targets in live animals or tissues. Its water solubility and stability enhance its utility in complex biological environments, making it a valuable tool in diagnostics, drug development, and cancer research. Additionally, it is employed in flow cytometry and microscopy for high-resolution imaging and analysis of cellular structures.