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Graphene oxide (GO) with outstanding mechanical properties is a satisfactory filler to reinforce artificial silk. To prepare tough regenerated silk fibroin/graphene oxide (RSF/GO) hybrid fibers, it is important to understand the structural evolution of the hybrid fibers with external deformation. The morphology and microstructural changes of the hybrid fibers at different tensile strains were investigated by SEM, Raman spectra and synchrotron radiation wide angle X-ray diffraction (SR-WAXD). Longer and deeper stripes were found on the surface of RSF/GO fibers with the increase of strain as revealed by SEM. SR-WAXD results revealed that the fraction and orientation of crystals and the mesophase had slight changes in the elastic deformation zone of the fiber. However, in the plastic deformation zone of the fiber with a strain from 5 to 18%, the fraction of crystals gradually increased while the fraction of the mesophase decreased. During this deformation, the orientation of crystals (fc) firstly increased significantly and then increased slightly, while the orientation of the mesophase (fm) increased steadily beyond the yield point. When the strain exceeded 18%, the fraction of crystals decreased while the fraction of mesophase increased. The fc had a rapid increase again at a strain above 18%. A model was proposed to explain how the tensile deformation affects the molecular orientation of the hybrid fibers.

To improve the therapeutic effect of a damaged peripheral nerve, aligned scaffolds based on regenerated silk fibroin (RSF) were fabricated by electrospinning, and were simultaneously loaded with dual factors of brain-derived neurotrophic factor (BDNF) and vascular endothelial growth factor (VEGF). An ELISA assay measurement in vitro demonstrated that the release of dual factors from the scaffolds was well maintained up to 2 weeks. Schwann cell (SC) morphologies on the RSF scaffolds were obtained using scanning electron microscopy (SEM) and laser scanning confocal microscopy (LSCM) after cell seeding. Cell viability and proliferation on the scaffolds were investigated using an MTT assay. Furthermore, the scaffolds were implanted in a mouse model to support nerve regeneration and angiogenesis in vivo, which was evaluated by histological and immunohistochemical (IHC) analyses at 4 and 8 weeks after implantation. In all retrieved scaffolds, de novo innervation and vascularization, indicated by a positive endothelial marker (von Willebrand factor, vWF) and an innervation marker (S-100 protein), were evident without chronic inflammatory responses. Compared to the control group, the dual-factor loaded scaffolds significantly promoted nerve regeneration and possessed great potential in peripheral nerve repair and regeneration, and for the repair of other tissues.

In this work, hydrogel photonic crystal beads with inverse opal structure are generated on a well-controlled microfluidic chip device. An online droplet drying method and templating technique are integrated into the producing process. This process results in the silica nanoparticles in the droplets self-assembled into spherical photonic crystals with narrow stop bands and identical structural colours, which is the ideal template for fabricating inverse opal hydrogel beads. The effects of acrylic acid (AA) concentration, water dosage and buffer pH on the equilibrium swelling of inverse opal hydrogel are discussed. In the concentration of AA (3%) and water (31%), the inverse opal hydrogel beads show wide sensing range and rapid response (less than 30 s) to pH variation. Overall, the inverse opal hydrogels as pH sensors show homogeneous structural colour changes due to the spherical 3D structure. The present characterization of quite mechanically robust and good reproducibility for the spherical pH sensor may have promise application in advanced optical devices.

Regenerated silk fibroin (RSF) scaffolds electrospun from aqueous solutions have great potential for tissue engineering. However, the traditional RSF mats are weak and limit the applications. A bladder acellular matrix graft (BAMG), a tough natural material, was used as an electrospinning substrate to toughen the RSF scaffolds. Compared with bare RSF scaffolds, the composite scaffolds with breaking energies ranging from 458 to 970 J kg−1 show significantly improved tensile properties and suture retention strength, which may satisfy the requirements for implantation. Vascular endothelial growth factor (VEGF) was encapsulated in the RSF/BAMG composite scaffolds by means of blend and coaxially electrospinning to promote the ability of vasculogenesis and angiogenesis. Transmission electron microscope (TEM) images show that the coaxially electrospun fibers had a core–sheath structure. An ELISA assay measurement indicates that VEGF can be released for more than 16 days. The samples annealed in water vapor exhibit higher release profiles than those immersed in ethanol. An in vitro assay indicates that VEGF loaded scaffolds evidently induced the attachment and proliferation of porcine iliac endothelial cells (PIECs) compared with those without VEGF. Moreover, the VEGF remained bioactive for up to 7 days. Thus the VEGF loaded composite scaffolds could be a promising candidate for tissue engineering applications.

In this paper, the structures and properties of regenerated silk fibroin (RSF) aqueous solutions under shear were investigated by using a polarizing microscope, an optical shearing instrument, a rotational rheometer, a Raman spectrometer and a synchrotron radiation small angle X-ray scattering facility. It was found that after being sheared at a constant shear rate for a suitable time, the RSF aqueous solution showed gradually decreased viscosity and enhanced birefringence before protein denaturation. Meantime, rod-like structures were formed and conformational transition happened in the solution. These results indicated that the RSF molecules in the solution might gradually form rod-like liquid crystal structures after applying sufficient shear. Moreover, it was also found that the increase of the shear rate could reduce the critical shear time for the solution to begin to form the liquid crystal structure.