[Property studies on three-dimensional porous blended silk scaffolds]

To explore the differences of three-dimensional porous blended silk scaffolds with different sericin ratios in terms of molecular structure, mechanical properties, and biological characteristics.

Fibroin/sericin blended aqueous solution [concentration 8% (W/V)] with various sericin ratios 0%, 2%, 4%, 6%, 8%, 10%, 12% and NaCl as a porogen with different particle sizes (125-200, 200-300, 300-450, 450-600, 600-900, 900-1100 microm) were used to fabricate the three-dimensional porous blended silk scaffolds. Gross observation of the formation of three-dimensional porous blended silk scaffolds of different sericin ratios and pore sizes was performed. Scanning electron microscope (SEM) was used to detect the distribution and diameter of the pore sizes. Its porosity was calculated by liquids replacement method. X-ray diffractometer (XRD) and fourier transform infrared (FTIR) were used to detect its internal molecular structure. Its mechanical properties, enzyme degration rate in vitro and experiment on SD rats in vivo, and histology observation after coculturing homogeneous scaffold (sericin ratio 0-12%, NaCl particle size 600-900 microm) with adipose tissue-derived mesenchymal stem cells (ADSCs) were detected.

Gross observation showed that the higher of the ratio of sericin protein, the greater of the porogen sizes scope which used to form homogeneous silk scaffolds. The result of SEM showed that the pores of the three-dimensional porous blended silk scaffolds had uniform distribution and was connected with each other. Its pore sizes was in the scope of the porogen sizes, and its porosity all above 90%. The angel corresponding to the characteristic peak of the sericin/fibroin blended scaffolds were 20.6 degrees and 24.6 degrees (XRD), and the wavelength corresponding to the characteristic peak of the sericin/fibroin blended scaffolds were 3 296, 2 933 and 1629 cm(-1) (FTIR) which was the same as the angel and wavelength corresponding to the characteristic peak of the natural silk. The mechanical properties of the sericin/fibroin blended scaffolds was improved with the increase of sericin ratios, and the compressional resilience reached 100% when the ratio > or = 6%. The different ratios of sericin and the different particle size of porogen had no significant effect on the enzyme degradation rate in vitro. The histological observation 14 days after ADSCs-scaffold co-culture indicated that the scaffolds had slow degradation rate, and slight inflammatory response in vivo. ADSCs were well attached to the sericin/fibroin blended scaffolds of different sericin ratios, with varied morphology, rich cytoplasm, and nuclear enrichment, the light staining ECM was observed surrounding the cells.

The mechanical property of the three-dimensional porous blended silk scaffolds is improved by silk sericins with ratio > or = 6% obviously, which will lay the groudwork for further research and making of strengthen silk scaffolds.