Used in bioconjugation to link molecules such as proteins, peptides, or drugs to other compounds while improving solubility and stability. The amine group (NH2) reacts easily with carboxylic acids, aldehydes, or activated esters, making it ideal for attaching biomolecules. The PEG spacer (polyethylene glycol) reduces aggregation, extends circulation time in vivo, and decreases immunogenicity. Commonly applied in drug delivery systems, diagnostic probes, and surface modifications of nanoparticles or medical devices. Also used in creating hydrogels and functionalized coatings where controlled release or biocompatibility is needed.