Cy5.5 ethylenediamine is widely used in biomedical research for fluorescence imaging due to its near-infrared emission properties, which allow deep tissue penetration and minimal background interference. It is commonly employed in labeling biomolecules such as antibodies, peptides, and nucleic acids for in vivo and in vitro imaging studies. This dye is particularly useful in tracking cellular processes, tumor targeting, and monitoring drug delivery systems. Additionally, its stability and high quantum yield make it suitable for sensitive detection in diagnostic assays and molecular imaging techniques.