Used in bioconjugation to link biomolecules such as peptides, proteins, or antibodies to surfaces or nanoparticles. The amine group reacts with carboxyl, aldehyde, or NHS-activated groups, while the carboxylic acid end allows further coupling or attachment to amine-containing substrates. Commonly applied in drug delivery systems, PEGylation of therapeutic proteins to improve solubility and stability, and in the development of biosensors and diagnostic assays. Its PEG spacer reduces non-specific binding and enhances biocompatibility.