Bioinspired Microstructured Ceramic-Hydrogel Composites with Controlled Release of Ca²⁺ and Mechanical Stability

Functional biomaterials are needed for many tissue engineering applications. Currently, most functional biomaterials are hydrogel-based, which poses issues in terms of mechanical stability, while the strong biomaterials are limited in terms of functional properties such as drug release. Here, we explore the fabrication and characterization of a ceramic-hydrogel composite system that exhibits a bioinspired microstructure, mechanical stability, prolonged calcium ion release, and no adverse biological effects. More importantly, relying on magnetized alumina microplatelets at about 50 vol %, held together with only 14 wt % of a hydrogel matrix containing sodium alginate, calcium can be encapsulated inside the composite and released over a 14-day period. The hydrated stiffness of the composites is of about 100 MPa, which is similar to various soft tissues, and the calcium releasing composites have demonstrated non-toxicity and good biocompatibility toward pre-osteoblast MC3T3 cells. While the ability to tailor the microstructure to mimic the natural tissue hierarchical organization is of interest, its specific effects have yet to be determined. Further tuning the microstructure for specific tissue replacement or repair could be explored by varying the chemistry of the microplatelets or of the hydrogel to design and fabricate microstructured functional and structural biomaterials.