NH2-PEG-COOtBu is widely used in bioconjugation and drug delivery systems due to its bifunctional nature. The amine group (NH2) allows for covalent attachment to various biomolecules, such as proteins, peptides, or antibodies, while the COOtBu group provides stability and can be deprotected to yield a carboxylic acid for further functionalization. This chemical is particularly valuable in creating PEGylated therapeutics, where it enhances solubility, prolongs circulation time, and reduces immunogenicity of drugs. Additionally, it is employed in the development of targeted drug delivery systems, enabling precise delivery of therapeutic agents to specific tissues or cells. Its versatility also extends to surface modification of nanoparticles, improving biocompatibility and stability for biomedical applications.