Amino-PEG4-CH2COOH is widely used in bioconjugation and drug delivery systems due to its hydrophilic PEG spacer and functional groups. The amino group allows for covalent attachment to biomolecules like proteins, peptides, or antibodies, while the carboxylic acid enables further modification or coupling to other molecules. Its PEG chain enhances solubility, reduces immunogenicity, and prolongs circulation time in biological systems. This compound is particularly valuable in creating targeted drug delivery systems, improving the stability and efficacy of therapeutic agents. It is also utilized in surface modification of nanoparticles and biomaterials to enhance biocompatibility and functionality. Additionally, it plays a role in the development of diagnostic tools and biosensors by facilitating the immobilization of biomolecules on surfaces.