Designing Porous Bone Tissue Engineering Scaffolds with Enhanced Mechanical Properties from Composite Hydrogels Composed of Modified Alginate, Gelatin, and Bioactive Glass

The combination of biodegradable polymers and bioactive inorganic materials is being widely used for designing bone tissue engineering scaffolds. Here we report a composite hydrogel system composed of bioactive glass incorporated in covalently cross-linked oxidized alginate-gelatin hydrogel (ADA-GEL) for designing porous scaffolds with tunable stiffness and degradability using freeze-drying technique. Because of the presence of bioactive glass, the cross-linking kinetic and cross-linking degree of the hydrogels are significantly increased, which is the main factor for the measured enhanced mechanical strength of the bioactive glass containing ADA-GEL scaffolds. The hydrogels with high cross-linking degree exhibit low protein release profile and low degradability. Apatite formation on bioactive glass containing hydrogel-based scaffolds is confirmed by FTIR. Bone marrow-derived stromal cell growth is promoted in pristine ADA-GEL and 1% bioactive glass containing ADA-GEL scaffolds compared to the scaffolds of pure alginate, alginate–gelatin blended hydrogel, and 5% bioactive glass containing ADA-GEL. Initial studies indicated that the scaffolds, especially without bioactive glass, support osteogenic differentiation of murine bone marrow stromal cell line in the absence of foreign osteogenic stimulating supplements; however, they exhibit low levels of osteogenic expression.