Controlling the Pore Structure of Collagen Sponge by Adjusting the Cross-Linking Degree for Construction of Heterogeneous Double-Layer Bone Barrier Membranes

Guided bone regeneration (GBR) has been regarded as a valuable way to effectively induce bone remodeling. The key factor of GBR is to place a barrier membrane between the soft tissue and bone defect, preventing the untimely intrusion of fibroblasts and permitting the prior settlement of internal osteoblasts. Notably, heterogeneous double-layer GBR membranes with a compact upper layer and a loose lower layer exhibit enhanced effectiveness in blocking fibroblasts and promoting the growth of osteoblasts. Herein, we present porous and interconnected collagen-based sponges with controllable pore size for the fabrication of absorbable GBR membranes with a heterogeneous double-layer structure. Dialdehyde carboxymethyl cellulose was used to fix collagen-based sponges. The pore size of the sponges can be well controlled by adjusting the cross-linking degree, which is decreased with an increase of cross-linking degree. The sponges show enhanced mechanical properties, inhibited swelling ability and biodegradation, good blood compatibility, and good cytocompatibility. The sponges are feasible to form a heterogeneous double-layer structure with a loose lower layer and a compact upper layer. Interestingly, the lower layer with the pore size of 200–300 μm can promote the adhesion, proliferation, and differentiation of osteoblasts MC3T3-E1 cells, while the upper layer with the pore size of 20–50 μm makes a great contribution to the growth of myoblast C2C12 cells. Overall, the collagen-based sponges have the potential to be used to fabricate heterogeneous double-layer bone barrier membranes for bone remodeling.