HAp granules encapsulated oxidized alginate–gelatin–biphasic calcium phosphate hydrogel for bone regeneration

Bone repair in the critical size defect zone using 3D hydrogel scaffold is still a challenge in tissue engineering field. A novel type of hydrogel scaffold combining ceramic and polymer materials, therefore, was fabricated to meet this challenge. In this study, oxidized alginate–gelatin–biphasic calcium phosphate (OxAlg–Gel–BCP) and spherical hydroxyapatite (HAp) granules encapsulated OxAlg–Gel–BCP hydrogel complex were fabricated using freeze-drying method. Detailed morphological and material characterizations of OxAlg–Gel–BCP hydrogel (OGB00), 25 wt% and 35 wt% granules encapsulated hydrogel (OGB25 and OGB35) were carried out for micro-structure, porosity, chemical constituents, and compressive stress analysis. Cell viability, cell attachment, proliferation and differentiation behavior of rat bone marrow-derived stem cell (BMSC) on OGB00, OGB25 and OGB35 scaffolds were confirmed by MTT assay, Live–Dead assay, and confocal imaging in vitro experiments. Finally, OGB00 and OGB25 hydrogel scaffolds were implanted in the critical size defect of rabbit femoral chondyle for 4 and 8 weeks. The micro-CT analysis and histological studies conducted by H&E and Masson's trichrome demonstrated that a significantly higher (***p < 0.001) and earlier bone formation happened in case of 25% HAp granules encapsulated OxAlg–Gel–BCP hydrogel than in OxAlg–Gel–BCP complex alone. All results taken together, HAp granules encapsulated OxAlg–Gel–BCP system can be a promising 3D hydrogel scaffold for the healing of a critical bone defect.