M-PEG4-DBCO is widely used in bioconjugation and click chemistry applications due to its DBCO (dibenzocyclooctyne) group, which reacts efficiently with azides without the need for a catalyst. This property makes it highly valuable in labeling biomolecules, such as proteins, peptides, and antibodies, for imaging, diagnostics, and targeted drug delivery. The PEG4 spacer enhances solubility and reduces steric hindrance, improving the efficiency of conjugation reactions. It is also employed in the development of antibody-drug conjugates (ADCs) and other therapeutic constructs, where precise and stable linkage between components is critical. Additionally, its application extends to surface modification of nanoparticles and materials for biomedical research and drug delivery systems.