Flexible silk fibroin films modified by genipin and glycerol

Silk fibroin (SF) films, modified by genipin (GP) and glycerol (Gl), with favourable mechanical properties, were obtained by a casting/solvent evaporation method. Simultaneously, the chemical, mechanical and structural properties of the films were examined and analyzed. Compared to uncrosslinked SF films, fibroin solubility of the modified SF (MSF) and Gl/MSF films in the warm water decreased dramatically from 46% to 15%, exhibiting good stability under a physiological environment. The best, valuable modified films with tensile strength of 18.0 MPa, breaking elongation of 171.1% and Young's modulus of 463.1 MPa were obtained when the GP and Gl content were both 20 wt% and relative to the amount of fibroin. The deformability of the MSF films augmented significantly by increasing the Gl concentration. Fourier transform infrared (FT-IR) results revealed that GP could react with SF macromolecules to form inter- and intra-molecular conjugated covalent bonds. Moreover, the FT-IR and X-ray diffraction (XRD) studies illustrated the GP induced conformational transition from random coil to β-sheet SF chains, yielding MSF and Gl/MSF films with enhanced stable thermal stability. The cytocompatibility of the MSF films were evaluated through MTT assay using L929 fibroblast. Compared to the SF films treated with 75% ethanol, the MSF films exhibited significant cytocompatibility, which was demonstrated by cell adhesion, proliferation and cell morphology. The intrinsic properties and biological results suggest that the MSF films may be potential candidate materials for wound dressing applications or tissue engineering strategies.