Dual thermal- and pH-responsive polypeptide-based hydrogels

Smart hydrogels have received increasing attention for their great potential for the applications in many fields. Herein, we report a facile approach to prepare a class of dual-responsive hydrogels assembled from synthetic statistical/block thermal-responsive copoly(L-glutamate)s copolymerized with poly(ethylene glycol), which were prepared by ring-opening polymerization (ROP) and post-modification strategy. The incorporation of oligo(ethylene glycol) (OEG) and glutamic acid residues offers the gels with thermal- and pH-responsive properties simultaneously. We have systematically studied the influence of both temperature and pH on the gelation behaviors of these copolymers. It is found that the increase of glutamic acid content and solution pH values can significantly suppress the gelation ability of the samples. Circular dichroism (CD) results show that the α-helix conformation appears to be the dominant secondary conformation. More interestingly, the gelation property of the block copolymer with statistical thermal-responsive copoly(L-glutamate)s shows greater dependence on pH as compared to that with block segments due to the distinct morphology of the self-assemblies. The obtained hydrogels exhibit pH-dependent and thermal-responsive gelation behaviors, which enable them as an ideal smart hydrogel system for biomedical applications.