Used as a heterobifunctional crosslinking agent in bioconjugation, particularly in the development of antibody-drug conjugates (ADCs). One end of the molecule contains an aldehyde group that selectively reacts with aminooxy or hydrazide groups under mild conditions, enabling conjugation to modified biomolecules. The other end features an active ester (NHS ester) that efficiently couples with primary amines on proteins or peptides. This dual reactivity allows for controlled, site-specific linkage between a targeting antibody and a cytotoxic drug or a fluorescent probe. Its hydrophilic spacer arm improves solubility and reduces aggregation in aqueous reaction environments, making it suitable for conjugations requiring high efficiency and minimal side reactions.