Rheological Studies of Shear Recoverable Peptide-based Beta Hairpin Hydrogel

摘要

The 20 amino acid peptide, MAX 1(VKVKVKVK-VDPPT- KVKVKVKV-CONH2) has a structure of two symmetry strands consisting of alternating hydrophobic valine residues and lysine residues, and a central tetrapeptide turn sequence. Such peptide sequence design enables MAX 1 to fold into a beta hairpin conformation as a result of being exposed to a desired environmental stimulus, say, change of pH[1], salt concentration[2] or temperature[3]. The consequent intermolecular assembly leads to a highly crosslinked hydrogel network. As a rigid material, one unique characteristic of the peptide hydrogel is that it can be processed (i.e. injected) by application of shear. When subjected to an appropriate shear stress, the hydrogel shear thins and flows like a liquid. However, the gel quickly self-heals and recovers its original stiffness right after removing the shear stress indicating potential applications in tissue engineering (i.e. 3D encapsulation and injectable delivery of cells). In this work, shear recovery experiments were performed on a stress-controlled rheometer over a variety of shear rates and shear time, respectively. The results qualitatively and quantitatively explain the changes that occur to the physical gel during shear-thinning as well as during the rehealing process. The mechanism of shear thinning in these self- assembled gels will be discussed.