Xinxing Feng

Structural Characteristics and Properties of Silk Fibroin/Poly(lactic acid) Blend Films

This paper describes the preparation and characterization of blend films composed of regenerated silk fibroin (SF) and poly(lactic acid) (PLA). FT-IR and XRD of the SF/PLA blend films with different ratios indicated that the secondary structural transition of SF from Silk I to Silk II was induced upon blending with PLA. The effects of SF/PLA blend ratios on the mechanical and physical properties of the blend films were investigated. Compared to pure SF film, the mechanical and thermal properties of the blend films were improved, and surface hydrophilicity and swelling capacity decreased due to the secondary structural transition of SF to Silk II. Among the blend films with different ratios, the SF/PLA blend film with 7 wt% PLA content showed excellent mechanical properties. Meanwhile, the BSA adsorption amount on the blend film increased with the increase of PLA content. In vitro cell adhesion test showed that the blend film was a good matrix for the growth of L929 mouse fibroblast cells. Consequently, controlling the PLA content in the SF film can improve the mechanical and physical properties of the SF film and provide a promising opportunity to widen potential application of SF in the biomaterials field.

Preparation and characterization of bioactive mesoporous calcium silicate–silk fibroin composite films

Composite films of bioactive mesoporous calcium silicate (MCS)/silk fibroin (SF) and conventional calcium silicate (CS)/SF were fabricated by the solvent casting method, and the structures and properties of the composite films were characterized. Results of field emission scanning electron microscope (FESEM) indicated that MCS or CS was uniformly dispersed in the SF films. The measurements of the water contact angles suggested that the incorporation of either MCS or CS into SF could improve the hydrophilicity of the composite films, and the former was more effective than the later. The bioactivity of the composite films was evaluated by soaking in a simulated body fluid (SBF), and the formation of a hydroxycarbonate apatite (HCA) layer was determined by XRD and FT-IR. The results showed that the MCS/SF composite films have significantly enhanced apatite-forming bioactivity compared with the CS/SF composite films owing to the highly specific surface area and pore volume of MCS. In vitro cell attachment and proliferation tests showed that the MCS/SF composite film was a good matrix for the growth of MG63 cells. Consequently, the MCS/SF composite film possessed excellent physicochemical and biological properties, indicating its potential application for bone tissue engineering by designing 3D scaffolds according to its corresponding composition.

Nano-TiO2 induced secondary structural transition of silk fibroin studied by two-dimensional Fourier-transform infrared correlation spectroscopy and Raman spectroscopy.

By sol–gel processing, regenerated nano-TiO2/SF (silk fibroin) composite films were synthesized. The experimental results revealed that the nano-TiO2 particles were well dispersed in the regenerated silk fibroin. Using FT-IR and Raman spectroscopy, the secondary structures of these composite films with concentrations of 0, 0.2, 0.4, 0.8 and 1.6 wt% were characterized. Concentration-perturbed two-dimensional (2D) correlation spectra were calculated for the spectra in the 1800–1600 cm−1 region. To investigate nano-TiO2 particles induced changes in the secondary structure and hydration, the slice spectra were calculated from the synchronous and asynchronous spectra, respectively. The transmittance IR and Raman spectra measurement indicated that the secondary structure of the pure silk film was mostly random coil and α-helix, while the composite films were β-sheet. With increasing nano-TiO2 content, the secondary structure of composite films was changed from typical Silk I to typical Silk II. However, it was found that the transition of the SFs secondary structures would be restrained by excessive nano-TiO2 (over 0.8%) introduced into the composite SF films. Through the FT-IR absorbance and 2D correlation spectra, it was demonstrated that the formation of nano-TiO2 particles could induce the partial transformation of SF conformation from Silk I to Silk II.