Light-Triggered Cross-Linking of Alginates with Caged Ca²⁺

A strategy to light-trigger ionic cross-linking of alginates by incorporating a photosensitive Ca²⁺ cage (nitr-T) is presented. Upon irradiation, free Ca²⁺ was released, and this caused gelation of the alginate solution. Addition of Ca²⁺ “on-demand” allowed us to obtain homogeneous alginate (ALG) gels using concentrated initial ALG solutions (10%), not possible with other ionic gelation approaches. The cross-linking degree and derived mechanical properties of the hydrogel were modulated by the exposure dose. The light-mediated cross-linked alginate hydrogel displayed a significant improvement in the mechanical properties and homogeneity when compared to mixtures of alginate and soluble Ca²⁺ at comparable concentrations