Shear-Thinning and Self-Recovery Hydrogel Inks Based on Alkyne-Functionalized Triblock Copolypeptide and PEG for Direct Ink Writing

Direct ink writing (DIW) hydrogel inks for biomedicine are expected to balance flowability during extrusion with stability after deposition while maintaining cytocompatibility. Herein, an alkyne-functionalized amphiphilic triblock copolypeptide composed of l-glutamic acid and l-phenylalanine residues was synthesized. In aqueous environments, the copolypeptide self-assembles spontaneously through the hydrophobically driven association of the l-phenylalanine blocks, resulting in a physically cross-linked network with tunable viscoelastic properties. This dynamic network imparts pronounced shear-thinning behavior and rapid self-recovery, facilitating continuous extrusion and DIW of hydrogel filaments with excellent shape retention. Additionally, alkyne-functionalized PEG was incorporated into the hydrogel ink as a reactive diluent to accelerate photo-cross-linking kinetics and improve printing fidelity. Following the printing process, the alkyne groups enable rapid thiol–yne photo-cross-linking under 405 nm light, thereby providing an additional covalent network that reinforces the printed structures and enhances their stability. In vitro cytocompatibility experiments further confirmed the favorable biocompatibility of the printed hydrogels. Overall, this hydrogel presents a cooperative copolypeptide/PEG design for DIW-printable and photocurable hydrogel inks, with potential relevance for future biomedical applications.