Widely used as a linker in bioconjugation processes, particularly in the development of antibody-drug conjugates (ADCs) for targeted cancer therapies. Its dual functional groups, amino and azido, enable efficient coupling with various biomolecules, such as proteins, peptides, and drugs, facilitating the creation of stable and specific conjugates. The polyethylene glycol (PEG) spacer enhances solubility and reduces immunogenicity, making it valuable in drug delivery systems. Additionally, it is employed in surface modification of nanoparticles and biomaterials to improve biocompatibility and targeting efficiency. Its application extends to click chemistry reactions, where the azido group participates in copper-catalyzed or strain-promoted azide-alkyne cycloadditions, enabling precise and rapid labeling or functionalization of molecules in research and diagnostics.