Tendon-mimicking anisotropic alginate-based double-network composite hydrogels with enhanced mechanical properties and high impact absorption

Tendons are anisotropic tissues with exceptional mechanical properties, which result from their unique anisotropic structure and mechanical behavior under stress. While research has focused on replicating anisotropic structures and mechanical properties of tendons, fewer studies have examined their specific mechanical behaviors. Here, we present a simple method for creating calcium-crosslinked alginate-based double-network hydrogels that mimics tendons by exhibiting anisotropic structure, high mechanical strength and toughness, and a distinctive "toe region" when stretched. The tendon-mimicking hydrogel was fabricated using alginate/polyacrylamide double-network embedded with various mesoporous silica particles, followed by pre-stretching and fixation. Our findings show that hydrogels embedded with high aspect-ratio rod-shaped mesoporous silica microparticles and subjected to multiple pre-stretching cycles in the elastic range, exhibited the most favorable mechanical properties, including a toe region, closely resembling natural tendons. The hydrogels exhibited elastic modulus of 13.3 MPa, tensile strength of 5 MPa, and toughness of 3.5 MJ m^-3, even in its swollen state. An impact absorption test demonstrated the hydrogel's high energy dissipation and damping capacity, effectively absorbing external forces and functioning similarly to tendons. These anisotropic composite hydrogels, with their superior mechanical properties, offer considerable potential for applications in artificial tissue engineering, particularly where tendon-like mechanical characteristics are needed.