Tuning Star Polymer Architecture to Tailor Secondary Structures and Mechanical Properties of Diblock Polypeptide Hydrogels for Direct Ink Writing.

Hydrogel three-dimensional (3D) printing has emerged as a highly valuable fabrication tool for applications ranging from electronics and biomedicine. While conventional hydrogels such as gelatin, alginate, and hyaluronic acid satisfy biocompatibility requirements, they distinctly lack reproducibility in terms of mechanical properties and 3D printability. Aiming to offer a high-performance alternative, here we present a range of amphiphilic star-shaped diblock copolypeptides of l-glutamate and l-leucine residues with different topologies. Hydrophobic side chains of the l-leucine polymer block drive conformational self-assembly in water, spontaneously forming hydrogels with tunable mechanical properties, through variation of star topology. Their amenable shear-thinning and self-recovery properties render them suitable as hydrogel inks for direct ink writing. Well-defined 3D-printed structures can be readily generated and rapidly photo-cross-linked using visible light (405 nm) after methacrylamide functionalization, while hydrogel inks demonstrate good biocompatibility with top-seeded and encapsulated MC3T3 cells.