Ductility and Porosity of Silk Fibroin Films by Blending with Glycerol/Polyethylene Glycol and Adjusting the Drying Temperature

Ductility and porosity of biofunctional films (BFFs) are critical properties for mechanical compliance and intercellular communication in tissue engineering. However, it remains a significant challenge to integrate these two key properties into BFFs. Herein, silk fibroin (SF) films with tunable ductility and porosity were prepared by adjusting the protein self-assembly process through combinations with glycerol (Gly) and polyethylene glycol 400 (PEG400) and regulating the film-casting temperature. Typically, among various conditions screened, the BFFs with a mass ratio of SF/PEG400/Gly of 10:5:3 (SPG1053) prepared at 4 °C exhibited remarkable ductility with a tensile strength of 2.7 ± 0.2 MPa and an elongation at break of 164.24 ± 24.20%, superior to films prepared from SF alone, SF/Gly, or SF/PEG400, demonstrating a synergistic plasticizing effect. Furthermore, the SPG1053 films prepared at 4 °C had a permeation efficiency of 56.32 ± 0.85% for fluorescently labeled dextran (dextran-TMR, MW: 10 kDa) after 204 h, significantly higher than films prepared at 20 °C (34.67 ± 3.63%) and 60 °C (15.4 ± 1.16%). Finally, the ductile and porous SPG1053 had excellent cell compatibility with human fibroblasts (Hs 865.SK). Given the demonstrated ductility, molecule-sieving property, and cytocompatibility, these new SPG films should offer new options for cell culture and tissue engineering.