Fabrication of Cell-Laden Hydrogel Microcapsules of Alginate and Chitin Fibrils Using Divalent and Trivalent Metal Ions

This open-access study reports the design of alginate–chitin nanofibril composite hydrogels crosslinked with divalent (Ca²⁺) and trivalent (Fe³⁺) ions. Electrospray fabrication yielded 200–500 µm microcapsules with tunable rheology and stability. Fe³⁺-gelled microcapsules exhibited higher storage and loss moduli than Ca²⁺ counterparts and retained structural integrity under physiological conditions due to coordinate covalent crosslinking of Fe³⁺ with alginate. Encapsulated NIH/3T3 fibroblasts remained > 80 % viable after 5 days, with Fe³⁺ systems showing enhanced proliferation and migration. The findings demonstrate that Fe³⁺ crosslinking significantly improves mechanical strength, biocompatibility, and potential for wound healing and drug-delivery applications.