Tunable supramolecular hydrogels from polypeptide-PEG-polypeptide triblock copolymers

A series of ABA triblock copolymers of poly(γ-(2-methoxy ethoxy)esteryl-glutamate)-block-poly(ethylene glycol)-block-poly(γ-(2-methoxy ethoxy)esteryl-glutamate) with poly(ethylene glycol) as middle hydrophilic B block and oligo(ethylene glycol)-functionalized polyglutamate (poly-L-EG2Glu) as terminal A blocks were prepared via ring-opening polymerization of EG2Glu N-carboxyanhydride (NCA). The resulting P(EG2Glu)-b-PEG-b-P(EG2Glu) triblocks can spontaneously form hydrogels in water. The intermolecular hydrogen bonding interactions between polypeptides blocks were responsible for the formation of gel network structure. These hydrogels displayed shear-thinning and rapid recovery properties, which endowed them potential application as injectable drug delivery system. The mechanical strength of hydrogels can be modulated by copolymer composition, molecular weight and concentrations. Also, it was found that the hydrogels’ strength decreased with temperature due to dehydration of polypeptide segments. Atomic force microscopy and scanning electron microscopy images revealed that these hydrogels were formed through micelle packing mechanism. Circular dichroism and Fourier transform infrared spectroscopy characterizations suggested the poly-L-EG2Glu block adopted mixed conformation. A preliminary assessment of drug release in vitro demonstrated the hydrogels can offer a sustained release of doxorubicin (DOX) and the release rate could be controlled by varying chemical composition.