3D printed β-sheet-reinforced natural polymer hydrogel bilayer tissue engineering scaffold

It remains a significant challenge to fabricate natural polymer (NP) hydrogels with anti-swelling ability and high strengths in the physiological environment. Herein, the β-sheet-reinforced NP hydrogel is developed by copolymerizing methacrylated gelatin (GelMA) and methacrylated silk fibroin (SFMA) in aqueous solution, followed by ethanol treatment (named GelMA-SFMA-AL). The β-sheets formed by SFMA can act as a stable physical crosslink to enhance the mechanical properties and prolong the degradation of the GelMA network. Importantly, the chemical crosslinking in the GelMA-SFMA hydrogel prevents excessive aggregation of hydrophobic β-sheets, thereby avoiding the formation of brittle hydrogel. The obtained GelMA-SFMA-AL hydrogels exhibit considerably enhanced mechanical properties (Young’s modulus: 0.89–3.68 MPa; tensile strength: 0.31–0.96 MPa; toughness: 0.09–0.63 MJ/m3; compressive modulus: 0.78–2.20 MPa; compressive strength: 2.65–5.93 MPa) compared with GelMA-SFMA hydrogels (Young’s modulus: 0.04–0.13 MPa; tensile strength: 0.04–0.07 MPa; toughness: 0.01–0.02 MJ/m3; compressive modulus: 0.03–0.09 MPa; compressive strength: 0.30–0.64 MPa). A bilayer osteochondral scaffold is constructed via digital light processing (DLP) three-dimensiaonl (3D) printing technology, comprising GelMA-SFMA@diclofenac sodium (DS)-AL as the top layer and GelMA-SFMA@bioactive glass (BG)-AL as the bottom layer. The bilayer hydrogel scaffold is demonstrated to support cell attachment and spreading, and facilitate osteogenic differentiation of rat bone marrow stem cells in vitro. In vivo implantation experiment suggests this bilayer scaffold is promising to be used for osteo-chondral tissue regeneration.