Used in bioconjugation to link molecules via amine groups, particularly in drug delivery and protein modification. Its PEG spacer enhances solubility and reduces aggregation. Commonly applied in creating antibody-drug conjugates (ADCs) and functionalizing nanoparticles. The NHS ester reacts efficiently with primary amines under mild conditions, making it suitable for labeling biomolecules like peptides and proteins. Stable in organic solvents, it allows for controlled conjugation in aqueous or mixed solvent systems.