N-Mal-N-bis(PEG4-amine) is widely utilized in bioconjugation and drug delivery systems due to its reactive maleimide group and polyethylene glycol (PEG) chains. The maleimide group enables selective and stable conjugation with thiol-containing molecules, such as cysteine residues in proteins or peptides, making it valuable for creating protein-drug conjugates or antibody-drug conjugates (ADCs). The PEG chains enhance solubility, reduce immunogenicity, and prolong circulation time in biological systems, which is critical for improving the efficacy of therapeutic agents. Additionally, it is employed in surface modification of nanoparticles or biomaterials to improve biocompatibility and targeting efficiency. Its applications also extend to diagnostics, where it is used to label biomolecules for imaging or detection purposes.