Composite hydrogel gellan gum-based materials with CaCO$_3$ vaterite particles

Background and Objectives: Hydrogels are cross-linked three-dimensional polymeric structures containing a large amount of water. Hydrogel materials based on natural and/or synthetic biocompatible polymers are capable of imitating the structure and properties of the extracellular matrix of living tissues. Therefore, hydrogel-based materials are widely studied and developed as functional materials in various fields of biology and medicine, including the creation of biomaterials for transplantation and tissue engineering. However, hydrogels have a number of disadvantages, such as a low biomineralization capacity, low biomechanical properties, and weak ability to form biointerface with hard tissues. These properties make hydrogel-based materials unsuitable for hard tissue engineering, particularly, bone regeneration. Currently, approaches to overcome these limitations, in particular, to improve the biological activity and biomineralization of hydrogels are currently being widely developed. Materials and Methods: This study reports an efficient approach of hydrogels mineralization based on the ultrasound-assisted synthesis of calcium carbonate CaCO$_3$ in the gellan gum hydrogel material. Results: The composite hydrogel materials based on the gellan gum with CaCO$_3$ micron-sized particles in the vaterite polymorph, uniformly distributed within the hydrogel matrix, have been obtained. The fraction of CaCO$_3$ in the hydrogel can easily be controlled by the number of ultrasound treatment procedures. The morphology and structure of the obtained hydrogel materials, especially the structure and distribution of the inorganic phase CaCO$_3$, have been studied by scanning electron microscopy and X-ray diffraction. Conclusion: The proposed strategy for the hydrogel mineralization allows for to create functional composite materials with the potential for application for the tissue engineering, especially bone regeneration.