methoxyPEG

Methoxy polyethylene glycol, commonly abbreviated mPEG, is a monomethyl ether derivative of poly(ethylene glycol). In mPEG, one end of the polymer chain is capped with a methoxy group, while the opposite end is available for further functionalization. Depending on the derivative, the free end may be a hydroxyl group or carry a reactive moiety such as an NHS carbonate, maleimide, aldehyde, or other functional group used for conjugation to biomolecules or surfaces.

mPEG is highly water-soluble and chemically inert under many biological conditions, factors that contribute to its widespread use in biotechnology and pharmaceuticals. Typical mPEG reagents span a broad range of molecular weights, from roughly 500 Da to tens of kilodaltons, and many derivatives are available with predefined end groups to suit specific conjugation strategies. The polymer’s hydrophilic corona can improve solubility, stabilize proteins, and reduce nonspecific interactions.

Applications of mPEG include PEGylation of therapeutic proteins and peptides to extend circulatory half-life, reduce immunogenicity, and improve pharmacokinetic profiles. It is also used to functionalize nanoparticles, liposomes, and biosensors, as well as to modify surfaces and create stealth coatings. Common conjugation chemistries involve amine groups on proteins (via NHS esters or carbonates) or thiols (via maleimide or related partners), enabling selective, mild coupling under aqueous conditions.

Safety and regulatory considerations generally reflect PEG’s long-standing use and favorable biocompatibility, though rare anti-PEG antibodies have been reported in some contexts. Overall, mPEG remains a versatile tool for improving solubility, stability, and biocompatibility in a wide range of bioconjugate applications.