Silk fibroin/PEG composite scaffolds for tissue engineering

Silk fibroin (SF) is a natural fibrous protein created by the B. mori silkworm used to design 3D-scaffolds for tissue engineering. Preliminary data indicated that the addition of low molecular weight PEG leads to composite materials which result more stable upon incubation in water. This work aimed to study the performances of 3D-scaffold made of PEG/SF in terms of mechanical properties and cell viability with respect of scaffold made of SF alone. The scaffolds were characterized in terms of molecular organization, morphology, resistance to cyclical compression and diffusivity capacity of oxygen through the scaffold upon incubation in a Dulbecco Modified Eagle Medium over a 4 week period. To evaluate the influence on cell adhesion and proliferation, mouse fibroblasts (L929) were plated on 300 μm thick slices and tested by MTT cell viability assay 24h, 48h and 72h after seeding. After sterilization by vapour steam under pressure, sponge-like structures with satisfactory internal interconnection and pores sizing from 50 to 100 µm were obtained. The resistance to compression resulted constant over time, even if the addition of PEG determined a softening of the scaffolds. During incubation, the oxygen diffusivity maintained the constant value of about 0.8 cm2/s × 10−6 in the case of SF/PEG600 scaffolds, whilst constantly diminished for SF scaffolds. CryoSEM images permitted to attribute this behaviour to a partial reorganization of the scaffold fibres. L929 adhered at the SF/PEG and significantly proliferated within 72h. No signs of toxicity were evident in this time interval. Hence, the SF/PEG composites, stabilizing the 3D-scaffolds architecture upon incubation, provide a favourable microenvironment for cell growth and, therefore, they can be used in tissue engineering.