Cy5.5-COOH (Cyanine 5.5 carboxylic acid) is a fluorescent dye that emits fluorescence at 710 nm upon excitation at 650 nm. Cy5.5-COOH possesses excellent spectral properties, including a narrow absorption spectrum, high sensitivity, and stability. Cy5.5-COOH can be used for bioimaging and disease diagnosis[1].