Hydrogels assembled from star-shaped polypeptides with a dendrimer as the core

Abstract

A second or fourth generation dendrimer with primary amine as the peripheral terminal group was first synthesized via Michael addition and thiol–yne addition. A series of star-shaped polypeptides was synthesized by ring opening polymerization (ROP) of γ-(2-(2-methoxyethoxy)ethyl) L-glutamate (L-EG₂Glu) N-carboxyanhydride (NCA) using the amine group terminated dendrimer as the initiator. Taking advantage of the well-defined dendrimer and ROP, the arm number and arm length can be easily controlled. These star-shaped poly(L-EG₂Glu) can spontaneously form hydrogels instead of micelles in water at low concentration. The critical gelation concentration (CGC) and hydrogel strength displayed a stronger dependence on arm numbers than the arm length under similar conditions. These properties can be easily modulated by varying the poly(L-EG₂Glu) arm length and arm number. The hydrogels showed shear thinning and rapid recovery properties. TEM and AFM characterization revealed that the hydrogel networks were constituted by entangled and branched fibrils.