Biomimetic Bacterial Cellulose-Enhanced Double-Network Hydrogel with Excellent Mechanical Properties Applied for the Osteochondral Defect Repair.

Although hydrogels based on biopolymers show many advantages, their low mechanical properties limit their applications in osteochondral tissue engineering. In this study, one part of our work aimed at preparing a high strength biohydrogel by using a double-network (DN) hydrogel system, which consisted of two interpenetrating polymer networks composed of γ-glutamic acid, lysine, and alginate, and meanwhile by incorporating bacterial cellulose into the DN structures. The results showed that compression modulus of the resultant hydrogel (0.322 MPa) was comparable with that of natural articular cartilage and swelling degree was greatly depressed by using these strategies. On this basis, a bilayer hydrogel scaffold based on the bionics principle for osteochondral regeneration was fabricated via chemical and physical cross-linking. Additionally, hydroxyapatite (HA) particles with two different sizes were introduced into the bilayer hydrogels, respectively: micro-HA in the top layer for promoting cartilage matrix deposition and HA nanocrystals in the bottom layer for enhancing compression modulus and osteogenesis. The osteochondral defect model of rabbits was used to evaluate the repair effect of the scaffolds with the bilayer structure, and the results showed such as-synthesized scaffolds had a good osteochondral repair effect.