Amino-PEG9-acid is widely used in bioconjugation and drug delivery systems due to its ability to link molecules while improving solubility and stability. It serves as a spacer in antibody-drug conjugates (ADCs), enabling controlled release of therapeutic agents. In peptide synthesis, it enhances water solubility and reduces aggregation. The compound is also employed in surface modification of nanoparticles, improving biocompatibility and targeting efficiency. Additionally, it plays a role in creating hydrogels for tissue engineering, providing a flexible and biocompatible matrix for cell growth. Its PEG chain offers prolonged circulation time in vivo, making it valuable in developing long-acting pharmaceuticals.