Multicomponent scaffold with hierarchical porosity for enhanced mechanical and bioactivity

Abstract

The repair of critical-sized bone defects remains challenging due to insufficient blood vessel formation and nutrient delivery. To overcome this limitation, we developed a porous organic/inorganic composite scaffold, named Micro-MP, through a combined strategy of H₂O₂ gas foaming and freeze-drying. The scaffold incorporates an oxidized dextran/gelatin (OD/Gel) hydrogel with magnesium calcium phosphate cement (MCPC), forming a double network stabilized by multiple weak interactions. H₂O₂ plays a dual role by serving as both an oxidizing agent that strengthens the crosslinked network and a foaming agent that creates interconnected macropores. Subsequent freeze-drying introduces micropores within the macropore walls, resulting in a hierarchical pore architecture. Remarkably, the scaffold maintains comparable mechanical strength before and after foaming, as the oxidative function of H₂O₂ enhances network density. Furthermore, H₂O₂ treatment promotes apatite deposition on scaffold surfaces and improves protein adsorption capacity, thereby enhancing the attachment, proliferation, and osteogenic differentiation of rat bone marrow stromal cells (rBMSCs). This strategy effectively resolves the problem of maintaining mechanical strength during the foaming process while increasing pore size, offering a promising approach for bone regeneration.