From biocompatible to biodegradable: Poly(ethylene glycol)s with predetermined breaking points

Abstract

Poly(ethylene glycol) (PEG) is the gold standard polymer for biomedical applications. PEG is known for its biocompatibility and antifouling properties and is widely used for bioconjugation. However, like other synthetic polymers in the field, PEG is not biodegradable, limiting its use for parenteral formulations and protein conjugation to a molecular weight range with a specific upper limit (commonly 40-60 kDa) to avoid polyether accumulation in human tissue. For these biomedical applications, but also for other purposes such as cleavable hydrogels and templates for porous membranes, several routes for the insertion of in-chain biocleavable moieties, such as acetals or disulfides, into PEG have been developed. Recently, the synthetic strategies have been extended from step-growth polymerizations of commercially available, telechelic PEGs to more sophisticated routes based on ethylene oxide (co)polymerizations, permitting the incorporation of predetermined breaking points at any position in the PEG chains. © Springer-Verlag Berlin Heidelberg 2013.