Alginate-based Composite Hydrogels Formed by In Situ CaCO3 Crystallization

Composite hydrogels based on polysaccharides are of high interest in the biomedical field due to their superior characteristics resulting from the combination of constituents' properties. Herein, we propose a new method for obtaining calcium alginate-calcium carbonate hydrogels, starting from an insoluble calcium alginate (ACa) aqueous dispersion which acts as a crystallization medium for the in situ growth of CaCO3 through ammonium diffusion in a hermetically closed desiccator. To further enhance the applicability of the proposed method, three-component composite hydrogels were obtained using ACa and nonstoichiometric polyelectrolyte complexes (NPECs) as the crystallization medium. The latter were obtained prior by the titration of a zein solution with two polysaccharides, namely, sodium alginate and chondroitin sulfate A, in different molar ratios. The resulting composite hydrogels were freeze-dried and further cross-linked with BTCDA. All of the hydrogels were characterized by SEM, XRD, and FTIR-ATR, and a MTS assay indicated a high cell viability for the cross-linked samples. All of the hydrogels obtained showed a highly organized network with uniform pores, having calcite as the main CaCO3 polymorph.