Tunable Hydrogels with Improved Viscoelastic Properties from Hybrid Polypeptides

Abstract

Hydrogels that can respond to a number of external stimuli and at the same time show impressive rheological properties are promising materials for a wide range of bioapplications. Here, we present a series of well-defined linear amphiphilic pentablock hybrid polypeptides of the ABCBA type, where A is poly(l-lysine), B is poly(l-histidine)-co-poly(γ-benzyl-l-glutamate), and C is poly(ethylene oxide) (PEO). The polymers were synthesized by the sequential primary amine ring-opening polymerization of N-carboxy anhydrides using bis amine poly(ethylene oxide) (PEO) as a bifunctional macroinitiator, and the length of all of the blocks was varied. The resulting materials formed novel extrudable in situ forming quickly self-healing hydrogels, responsive to the alteration of pH and increase of temperature. The connection between the alteration of the secondary structure of the polypeptides with the viscoelastic behavior was revealed by means of rheology and circular dichroism. Small-angle neutron scattering and scanning electron microscopy were employed to shed light on the structure of the polymers and how it affects their rheological properties. The obtained polymers were subjected to enzymatic degradation tests with trypsin and leucine aminopeptidase. The results suggest that these biomaterials have the potential to be used in a number of bioapplications like drug delivery, 3D printing, and tissue engineering.