Used in bioconjugation to link proteins, peptides, or nanoparticles via thiol groups, providing water solubility and enhanced stability. Commonly applied in drug delivery systems, PEGylation of therapeutic proteins, and development of antibody-drug conjugates (ADCs). The maleimide end selectively reacts with cysteine residues, while the PEG spacer reduces aggregation and extends circulation time in vivo. Also utilized in surface modification of gold nanoparticles and hydrogels for biomedical applications.