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/m 3 ; 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/m 3 ; 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.