Facile Synthesis of Rapidly Degrading PEG-Based Thiol-Norbornene Hydrogels.

An alternate synthesis route was developed to prepare norbornene-functionalized poly(ethylene glycol) (PEG) from reacting multiarm PEG with carbic anhydride. The macromer, PEGNB, permits photo-cross-linking of thiol-norbornene hydrogels with kinetics comparable to conventional PEGNB macromer. In addition, PEGNB provides an additional carboxylate group for further conjugation with amine-bearing molecules. Interestingly, PEGNB thiol-norbornene hydrogels are highly susceptible to hydrolytic degradation through enhanced ester hydrolysis. The ester linkage is further weakened after the secondary conjugation, resulting in extremely rapid degradation of PEGNB hydrogels. More importantly, the degradation can be readily adjusted via tuning macromer compositions, with complete degradation time ranging from hours to weeks. The PEGNB hydrogels are also highly cytocompatible toward various cell types, providing opportunities for future applications in tissue engineering and advanced biofabrication.