Hierarchical Programming of Peptide Hydrogels via Electrostatic Coassembly and Dityrosine Cross-Linking

The extracellular matrix in living tissues undergoes dynamic mechanical changes that govern fundamental processes in development and disease, yet most synthetic hydrogels are mechanically static and cannot reproduce this programmability. Here, we report a covalent-supramolecular hybrid peptide hydrogel platform that enables two-stage, hierarchical stiffening. A family of short peptides undergoes electrostatic coassembly to form a supramolecular network, producing an order-of-magnitude increase in initial stiffness. Subsequent light-induced dityrosine cross-linking introduces a second, covalent stiffening phase. Remarkably, simple repositioning of tyrosine residues directs the final material architecture: one design yields stiffening fibrous hydrogels, whereas another generates cell-internalized nanospheres. This work demonstrates precise control over mechanical and structural outcomes, providing a programmable bioinspired building block for the development of dynamic biomaterials.