Alginate-based Composite Hydrogels Formed by In Situ CaCO₃Crystallization

Abstract

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.