Maleimide-PEG2-succinimidyl ester is widely used in bioconjugation and protein modification. Its maleimide group reacts specifically with thiol groups (-SH) in cysteine residues, while the succinimidyl ester reacts with primary amines (-NH2) in lysine residues or at the N-terminus of proteins. This dual reactivity makes it a valuable crosslinker for creating stable covalent bonds between proteins, peptides, or other biomolecules. It is commonly employed in antibody-drug conjugates (ADCs), where it links therapeutic agents to antibodies for targeted drug delivery. Additionally, it is used in surface modification of nanoparticles, biosensor development, and immobilization of biomolecules on solid supports for diagnostic or research purposes. Its PEG spacer enhances solubility and reduces steric hindrance, improving the efficiency of conjugation reactions.