Bioinspired Spider Silk Hydrogels and Xerogels with Programmable Mechanical Properties: Molecular Dynamics Simulations Study

Spider silk fibers are versatile building blocks for supramolecular self-assembly, yet the molecular determinants governing their collective mechanics remain poorly understood. Here, we use molecular dynamics simulations to elucidate how dityrosine cross-linking, pressure, and solvent environment control the structure, porosity, and mechanical response of spider silk-based xerogels and hydrogels. By systematically varying the fraction of covalently cross-linked fibers (0–100%), we identify three conformational regimes in silk fibers: compact, moderately extended, and highly extended, arising from cross-linking-induced modulation of intrachain hydrogen bonding and β-sheet formation. We observe that fully cross-linked networks exhibit lower stiffness than partially cross-linked assemblies, revealing a nonmonotonic relationship between cross-link density and Young’s modulus. All xerogel systems studied here sustain strains up to 40% without fracture, while strain-dependent pore evolution and cyclic hysteresis highlight the role of compositional heterogeneity in energy dissipation. The tunable mechanical and structural properties of these supramolecular assemblies could possibly make them suitable as a stretchable, biocompatible material for ocular applications, such as contact lens design.