No abstract

Novel tissue engineering scaffold materials of nano-hydroxyapatite (nHA)/silk fibroin (SF) biocomposite were prepared by freeze-drying. The needle-like nHA crystals of about 10 nm in diameter by 50-80 nm in length, which were uniformly distributed in the porous nHA/SF scaffolds, were prepared by a co-precipitation method with a size. The as-prepared nHA/SF scaffolds showed good homogeneity, interconnected pores and high porosity. XRD and FT-IR analysis suggested that the silk fibroin was in beta-sheet structure, which usually provides outstanding mechanical properties for silk materials. In this work, composite scaffolds containing as high as 70% (w/w) nHA were prepared, which had excellent compressive modulus and strength, higher than the scaffolds at low nHA content level and other porous biodegradable polymeric scaffolds often considered in bone-related tissue engineering reported previously. The cell compatibility of composite scaffolds was evaluated through cell viability by MTT assay. All these results indicated that these nHA/SF scaffold materials may be a promising biomaterial for bone tissue engineering.

Bombyx mori silk fibroin (SF) is known to be capable of facilitating nucleation of the hydroxyapatite crystals (HAps). To find out how SF mediates the nucleation of HAps, self‐assembly of SF in 1.5 simulated body fluid (SBF) was observed in this study through design of a co‐solution of SF and 1.5‐times SBF (SF/1.5 SBF). After the co‐solution of SF/1.5 SBF was incubated at 37.2 °C up to 7 days, SEM, X‐ray, and Fourier transform infrared (FTIR) observations indicated that nucleation of HAps was increased. In addition, the structure of SF was transited from random coil into β‐sheet indicated by FTIR spectra. The β‐sheet assembly of SF in 1.5 SBF was also supported by CD spectra. Atomic force microscopy provided detailed progress of the self‐assembly that SF incubated in 1.5 SBF was self‐assembled in the form from dot, through rod to final net. Therefore, this study suggested that nucleation of HAps of SF was controlled by its molecular self‐assembly. © 2013 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2013

An environmental physical method described herein was developed to improve the tensile properties of Bombyx mori cocoon sericin films, by using the plasticizer of glycerol, which has a nontoxic effect compared with other chemical crosslinkers. The changes in the tensile characteristics and the structure of glycerolated (0–40 wt% of glycerol) sericin films were investigated. Sericin films, both in dry and wet states, showed enhanced tensile properties, which might be regulated by the addition of different concentrations of glycerol. The introduction of glycerol results in the higher amorphous structure in sericin films as evidenced by analysis of attenuated total reflection Fourier transform infrared (ATR-FTIR) spectra, thermogravimetry (TGA) and differential scanning calorimetry (DSC) curves. Scanning Electron Microscopy (SEM) observation revealed that glycerol was homogeneously blended with sericin molecules when its content was 10 wt%, while a small amount of redundant glycerol emerged on the surface of sericin films when its content was increased to 20 wt% or higher. Our results suggest that the introduction of glycerol is a novel nontoxic strategy which can improve the mechanical features of sericin-based materials and subsequently promote the feasibility of its application in tissue engineering.

A novel silk fibroin spongy wound dressing (SFSD) incorporated with nano-Ag particles was prepared by coagulating with 1.25-5.0% (v/v) poly(ethylene glycol diglycidyl ether) (PGDE). The mechanical properties, moisture permeability and hygroscopicity of SFSD, and the nano-Ag release behavior from SFSD were evaluated. The results showed that the soft SFSD had satisfying tensile strength and flexibility, as well as excellent moisture permeability and absorption capability of wound exudates. The moisture permeability was 101 g/m(2) per h and the water absorption capacity of SFSD was 595.2% and 251.9% of its own weight in dry and wet states, respectively. The nano-Ag in the SFSD was released continuously at a relatively stable rate in PBS resulting in a remarkable antibacterial property. A rabbit model was used to dynamically observe the healing process of full-thickness skin defects. Full-thickness wounds were created on the dorsal side of rabbits, which were covered with SFSD and porcine acellular dermal matrix (PADM) for comparison. The mean healing time of the wounds covered with SFSD was 17.7 ± 2.4 days, significantly shorter than that with PADM. The histological analysis showed that the epidermal cell layer formed with SFSD was very similar to normal skin, suggesting that SFSD may provide a good component for the development of new wound dressings.