Strengthening of a hydrogel via silk nanofiber biomineralization and unilateral reverse dialysis

Hydrogels are three-dimensional network materials that have vast application potential in bone tissue engineering given their unique physical and chemical properties. However, compared with natural bones, the mechanical strength and stiffness of existing hydrogels are difficult to meet the requirements of mechanical support in bone repair at load-bearing sites. Inspired by biomineralization and semipermeable cell membrane osmotic pressure regulation, herein, the organic-inorganic mineralized copolymer (SNF/CaP) was introduced into a polyvinyl alcohol (PVA) network and unilateral reverse dialysis was used to regulate the interaction between the PVA chains and SNF/CaP to improve the mechanical properties of the hydrogel. The effects of different pH conditions on the type of calcium phosphate formed on silk nanofibers were studied. Under mineralization conditions of pH 5 and unilateral reverse dialysis, the prepared nanofiber mineralized PVA (PSH) hydrogel exhibited a densely layered structure. The tensile strength and toughness of the prepared PSH hydrogels could reach 70.87 MPa and 309.07 MJ/m³, respectively, which were 3.77 times and 3.30 times higher than those of PVA hydrogels (only PVA by unilateral reverse dialysis) and PS hydrogels (PVA and silk nanofibers by unilateral reverse dialysis), respectively. The mechanical properties of the PSH hydrogels following water absorption balance still matched those of human cartilage (8.1-40 MPa) and were better than most of the reported PVA-based hydrogels. In addition, the PSH hydrogel demonstrated excellent biocompatibility and has potential application value in cartilage tissue engineering.