Tough, self-healing, and injectable dynamic nanocomposite hydrogel based on gelatin and sodium alginate

Biomacromolecules based injectable and self-healing hydrogels possessing high mechanical properties have widespread potential in biomedical field. However, dynamic features are usually inversely proportional to toughness. It is challenging to simultaneously endow these properties to the hydrogels. Here, we fabricated an injectable nanocomposite hydrogel (CS-NPs@OSA-l-Gtn) combined with excellent autonomous self-healing performance and high mechanical strength by doping chitosan nanoparticles (CS-NPs) into dynamic polymer networks of oxidized sodium alginate (OSA) and gelatin (Gtn) in the presence of borax. The synergistic effect of the multiple reversible interactions combining dynamic covalent bonds (i.e., imine bond and borate ester bond) and noncovalent interactions (i.e., electrostatic interaction and hydrogen bond) provided effect energy dissipation to endure high fatigue resistance and cyclic loading. The hydrogel exhibited excellent mechanical properties like maximum 2.43 MPa compressive strength, 493.91 % fracture strain, and 89.54 kJ/m 3 toughness. Moreover, the injected hydrogel could withstand 150 successive compressive cycles after self-healing. Besides, the bovine serum albumin embedded in CS-NPs could be sustained release from the nanocomposite hydrogel for 12 days. This study proposes a novel strategy to synthesize an injectable and self-healing hydrogel combined with excellent mechanical properties for designing high-strength natural carriers for sustained protein delivery.