NH2-PEG-COOH is widely used in bioconjugation and surface modification due to its bifunctional nature. The amine group (-NH2) allows for covalent attachment to molecules like proteins, peptides, or drugs, while the carboxyl group (-COOH) enables further functionalization or coupling to other entities. In drug delivery systems, it serves as a linker to improve solubility, stability, and biocompatibility of therapeutic agents. It is also employed in the development of hydrogels and nanoparticles for controlled release applications. Additionally, it is utilized in surface coating to reduce non-specific binding in biosensors and diagnostic assays, enhancing their sensitivity and specificity.