Injectable Gellan Gum/Elastin-Based Nanocomposite Hydrogels as Filling Biomaterials for the Regeneration of Irregular Bone Defects.

Irregular bone defects present a major challenge in clinical treatment. Traditional bone grafts are often used but come with limitations, including poor conformity to defect shapes and incomplete healing. Injectable hydrogels have emerged as a promising alternative, as they can completely fill defects and conform to irregular geometries. In this study, injectable hydrogels were developed using methacrylated gellan gum and soluble elastin derivatives. These polysaccharide/protein-based materials exhibit shear-thinning behavior and can be photo-crosslinked in situ, as confirmed by rheological analysis. The hydrogels are easily administered into irregular bone defects and solidified with light, resulting in improved stability and viscoelastic properties. Elastin derivatives enhance cell adhesion, supporting cell colonization. To further promote bone regeneration, ZnO and β-tricalcium phosphate (β-TCP) nanoparticles were incorporated into the hydrogel matrix. These bioactive fillers impart osteoconductive and osteoinductive properties without altering the mechanical integrity of the base material. Notably, β-TCP scaffolds modulated alkaline phosphatase activity in mesenchymal stromal cells, and ZnO further boosted this osteogenic marker. Overall, these injectable, photo-crosslinkable hydrogels offer a versatile platform for bone tissue engineering by functioning as defect fillers and bioactive scaffolds, supporting both structural and biological requirements for bone regeneration.