A uniform-unsaturated crosslinking strategy to construct injectable alginate hydrogel

The controllable crosslinking between the constituting building blocks plays a key role in endowing the hydrogel with injectability through the formation of a uniform 3D interconnected network. Herein, a uniform-unsaturated crosslinking strategy has been devised to quickly construct injectable sodium alginate (SA) hydrogels. Under vigorous stirring, a moderate amount of metal ions can uniformly coordinate with the guluronate moieties of SA molecules, avoiding the locally excessive crosslinking and the loss of injectability caused by traditional dropping and soaking methods. The injectability of SA hydrogels can be regulated by easily adjusting the concentration of metal ions, and 0.2% (w/v) is the optimal concentration of CaCl2 for the preparation of injectable SA-Ca hydrogel. Meanwhile, multiple metal ions mediated crosslinking also has been achieved conveniently, expanding the functions. Importantly, SA hydrogels can function as the general platform of composites made of various molecules and materials, for targeting drug delivery, tissue repair, wound infection treatment, and so on. Further, injectable SA-0.2%Cu hydrogel as a model to treat wound infections can promote the healing of fullthickness skin. This study provides a super facile and universal strategy to prepare various SA injectable hydrogels with low cost, which hold great potential in biomedical applications and clinical transformation.