Fabrication of Double‐Network Hydrogel Based on <i>N,O</i> ‐carboxymethyl chitosan, Aldehyde Hyaluronate, and Alginate for 3D Bio‐Ink Applications

This study fabricates and characterizes novel double-network hydrogels for 3D bio-ink applications, combining N,O-carboxymethyl chitosan (NOCC), aldehyde hyaluronate (AHy), and alginate (Alg). The initial Schiff base-cross-linked network (NOCC-AHy-Alg) is enhanced with a second ionic Ca²⁺ cross-linking, optimized via an internal suspension method (CaCO₃/glucono-δ-lactone). Optimal parameters are 0.2 m CaCO₃ and 0.1 m glucono-δ-lactone with a 1-h immersion, proving superior to external CaCl₂ immersion. This internal approach yields a more robust network with improved compressive strength, dimensional stability, and lower porosity, requiring sustained Ca²⁺ for long-term stability. The hydrogels also demonstrate excellent self-recovery and energy dissipation, indicating potential for 3D printing. In vitro studies confirm biocompatibility with L929 and AT-MSCs. Overall, these double-network hydrogels show significant promise as advanced bio-inks for tissue engineering and other biomedical uses.