Poly(vinyl Alcohol) (PVA)-Based Hydrogel Scaffold with Isotropic Ultratoughness Enabled by Dynamic Amine–Catechol Interactions

Hydrogels, serving as promising load-bearing materials, often suffer from limited long-term stability due to their insufficient mechanical strength. One of the viable methods is to engineer hydrogels with muscle-like anisotropic structures to enable mechanical reinforcement along the alignment direction (e.g., artificial tendons) while sacrificing the mechanical strength in the perpendicular direction. However, for connective tissues such as the fibrous membranes of the articular capsule with fibers interwoven to resist excessive stretching and distension in multiple directions, isotropic mechanical strength is highly demanding. In this work, inspired by the dynamic amine-catechol interactions derived from mussel foot proteins (Mfps), an innovative strategy is developed to incorporate Mfps-like conjugates as elastic connections into the poly(vinyl alcohol) (PVA) matrix, mimicking the multidirectional fibrous bundles of connective tissues. Superior isotropic tensile strength (13.3 ± 0.5 MPa), ultratoughness (60.1 ± 2.6 MJ/m3), and resilience are achieved in this hydrogel, which surpasses most of the reported biocompatible hydrogels. Additionally, this hydrogel exhibits diverse functionalities such as underwater adhesion and conductivity due to the multiple dynamic amine-catechol interactions engineered in the hydrogel. The versatility of this hydrogel offers a broad range of possibilities as artificial scaffolds with enhanced isotropic mechanical strength and cell affinity for the long service term.