Carboxy-PEG5-sulfonic acid is widely used in bioconjugation and surface modification due to its reactive carboxylic acid group and hydrophilic PEG spacer. It is particularly valuable in creating water-soluble drug conjugates, enhancing the solubility and stability of therapeutic molecules. In material science, it is employed to modify surfaces, improving biocompatibility and reducing non-specific binding in biomedical devices. Additionally, it serves as a linker in peptide synthesis and protein engineering, enabling controlled attachment of functional groups. Its sulfonic acid moiety also makes it useful in ion-exchange applications and as a stabilizer in nanoparticle formulations.