Spider Silk Inspired Hierarchical Fibrous Hydrogels with Extreme Robustness via a Top-Down Multidimensional Engineering Strategy

Abstract

Conventional hydrogels often suffer from weak and fragile natures, limiting their uses in mechanically demanding areas. By contrast, spider silk hold impressive strength and toughness owing to its hierarchical structure. Inspired by spider dragline fiber, the boundaries of conventional hydrogels are broken by introducing hierarchical structures in chitosan fibrous hydrogels (FHCS) via a top-down multidimensional engineering strategy. Each level of hierarchical structure is introduced in different approaches: macroscopic fibers are fabricated via electrospinning; microscopic fibrillar structures are introduced based on “sea-islands” phase separation structure; chitosan anhydrous crystallites at the molecular level are induced by hydrogen bonding reconstruction. Through this strategy, the resulting hierarchical FHCS exhibits extreme mechanical properties (fracture strength: 47.0 ± 2.4 MPa; Young's modulus: 5.6 ± 2.4 MPa; fracture toughness: 12.3 ± 1.5 MJ m−3), simulating the mechanical properties of cartilage tissue. FHCS also shows good biocompatibility, biodegradability, and modulation on cell spreading and phenotypes via mechanotransduction pathway. Overall, FHCS emerges as a promising material in the mechanically demanding areas of biomedical fields. Besides, the top-down multidimensional engineering strategy provides fresh perspectives for creating hierarchical materials.