Cy5.5 diacid, SE is widely used in biomedical research for fluorescence imaging and diagnostics. Its near-infrared fluorescence properties make it ideal for in vivo imaging, allowing deep tissue penetration with minimal background interference. It is commonly conjugated to antibodies, peptides, or other biomolecules to target specific cells or tissues, enabling real-time visualization of biological processes such as tumor growth, inflammation, or drug delivery. Additionally, it is employed in molecular imaging studies to track cellular interactions and monitor therapeutic efficacy in preclinical models. Its stability and brightness also make it suitable for flow cytometry and microscopy applications.