Facile exfoliation of natural silk nanofibrils for homogeneous reinforced composites

Abstract Regenerated silk fibroin (SF) as a biomaterial has attracted increasing attention due to its outstanding biocompatibility and processibility. However, it faces great challenges in practical application because of the deterioration of the intrinsic mechanical properties of natural silk during the regeneration process. Natural silk nanofibrils (SNFs) has a typical hierarchical structure and maintains excellent mechanical properties of natural silk. Based on principle of homogeneous reinforced composites, herein, the SNFs were isolated as a reinforcing material and regenerated SF as matrix material to fabricate high‐performance SF nanocomposites. The SNFs with diameters ranging from 100 to 600 nm were prepared with yields of 87%. They not only maintained the crystallinity of natural silk, but also remained high stability in acid and alkaline solutions. Thanks to homogenous reinforcement of the SNFs, the tensile stress of the reinforced film was up to 2.2 MPa, the strain was 129%, and the water absorption was 50% in wet state. In vitro, the reinforced films supported adhesion and proliferation of human umbilical vein endothelial cells, which has potential in the application of biomedical dressings. Highlights Natural silk nanofibrils (SNFs) were exfoliated using a facile approach. The SNFs reinforced the silk nanocomposites significantly. The silk nanocomposites showed remarkable cytocompatibility. Homogeneous reinforcement is useful strategy to fabricate nanocomposites.