What are linear, branched, forked, and multiarm PEGs?

Linear PEGs are straight-chained PEGs that are either monofunctional, homobifunctional, or heterobifunctional.

• Linear monofunctional PEGs (mPEG-X) have one reactive moiety at one end of the PEG with the other end considered non-reactive (typically end-capped with a methoxy group)

• Linear homobifunctional PEGs (X-PEG-X) contain the same reactive moiety at each end of the PEG.

• Linear heterobifunctional PEGs (X-PEG-Y) contain a different reactive moiety at each end of the PEG.

Branched PEGs (PEG2-X), also referred to as “Y-shaped” branched PEGs, contain two PEGs attached to a central
core, from which extends a tethered reactive moiety.

Forked PEGs (PEG-X2) contain a PEG with one end having two or more tethered reactive moieties extending from a
central core.

Multi-arm PEGs (2-arm, 3-arm, 4-arm, 8-arm PEG-X) are based upon ethyoxylation of either glycerine (3-arm), pentaerythritol (4-arm), or hexaglycerine (8-arm). The 2-arm PEG was previously noted under the linear homobifunctional and heterobifunctional PEGs. Each arm has a tethered reactive group on the end. These multifunctional PEGs offer the potential to increase potency of the resulting conjugate by attaching multiple drug
molecules to each arm of the PEG.

Multifunctional PEGs have several applications, including linking macromolecules to surfaces (for immunoassays, biosensors, or various probe applications), hydrogel formation, and drug targeting, as well as targeting liposomes and viruses.

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