Used in bioconjugation and drug delivery systems due to its dual propargyl groups and disulfide linker. Enables click chemistry reactions, particularly copper-catalyzed azide-alkyne cycloaddition (CuAAC), for efficient coupling with azide-containing molecules. The PEG spacers enhance solubility and flexibility, improving bioavailability and reducing aggregation. The disulfide (SS) bond is cleavable under reducing conditions, such as in intracellular environments, allowing controlled release of therapeutic agents. Commonly employed in the synthesis of antibody-drug conjugates (ADCs), targeted nanoparticles, and stimuli-responsive polymers. Also useful in surface functionalization and crosslinking of biomaterials.