Used in bioconjugation for labeling biomolecules such as proteins and antibodies due to its reactive NHS ester group that binds primary amines. Commonly applied in fluorescence-based assays and imaging because it exhibits strong red fluorescence with high photostability. Ideal for cellular tracing and flow cytometry where bright, stable signals are required. Also employed in the development of diagnostic probes and fluorescent sensors thanks to its excellent chemical stability and compatibility with aqueous environments.