Supramolecular hydrogels assembled from nonionic poly(ethylene glycol)-b-polypeptide diblocks containing OEGylated poly-l-glutamate

Abstract

A poly(ethylene glycol)-b-poly(γ-(2-methoxyethoxy)esteryl-L-glutamate) (PEG-b-poly-L-EG₂Glu) diblock was prepared by the ring-opening polymerization (ROP) of L-EG₂Glu N-carboxyanhydride (NCA) using PEG–NH₂ as the macroinitiator. When the average degree of polymerization (DP) for poly-L-EG₂Glu was below 40, the PEG-b-poly-L-EG₂Glu diblock could spontaneously form hydrogels in water. For the different diblocks, a thermally-induced increase in mechanical strength was observed for the PEG-b-poly-L-EG₂Glu diblock between 20–45 °C. Transmission electron microscopy (TEM) and atomic force microscopy (AFM) revealed that continuous networks of nanoribbons were formed in these hydrogel samples. Circular dichroism (CD) and Fourier transform infrared spectroscopy (FTIR) characterization suggested that the formation of sufficient β-sheet content accounted for the nanoribbon assemblies and hydrogel networks. The minimal gelation concentration and gel mechanical properties were found to strongly depend on the composition of the PEG-b-poly-L-EG₂Glu diblocks.