Sulfo-Cy7 diacid is widely used in biomedical research as a near-infrared (NIR) fluorescent dye. Its application includes labeling biomolecules such as proteins, peptides, and antibodies for imaging and tracking in vivo and in vitro studies. The dye's NIR emission range (750-850 nm) minimizes background interference from biological tissues, making it ideal for deep-tissue imaging and real-time monitoring of biological processes. It is also employed in fluorescence microscopy, flow cytometry, and small animal imaging to study tumor targeting, drug delivery, and cellular interactions. Additionally, its water solubility and low toxicity enhance its suitability for biological applications.