M-PEG4-sulfonic acid is widely utilized in bioconjugation and chemical synthesis due to its water solubility and ability to modify biomolecules. It is commonly employed in the development of drug delivery systems, where it enhances the solubility and stability of therapeutic compounds. The sulfonic acid group allows for strong interactions with proteins and peptides, making it valuable in protein modification and labeling applications. Additionally, it is used in the preparation of hydrogels and polymers for biomedical applications, where its hydrophilic properties improve biocompatibility. Its role in click chemistry and crosslinking reactions further extends its utility in creating functional materials and bioactive surfaces.