Papers by Author: Tetsuo Asakura

Abstract: In recent years, electrospinning has received much attention to prepare porous tubular scaffold due to electrospun nanofibers mat, which can mimic the structure characteristics of the extracellular matrix (ECM). In the present paper, silk fibroin (SF) tubular scaffolds with small-diameter were prepared by electrospinning from regenerated silk fibroin (RSF) aqueous solutions with rotating mandrel collector. The morphology and fiber diameter distribution of SF tubular scaffolds were influenced much by the concentration of regenerated silk fibroin (RSF) solution, collecting distance and mandrel diameter. The results showed that SF tubular scaffold, which was in flat surface with smaller fiber diameter and uniform distributed, could be obtained at the concentration of 22%, collection distance of 10 cm and mandrel diameter of 4 mm. The structure of SF tubular scaffolds before and after ethanol treatment was characterized by FTIR and XRD. After ethanol treatment, the SF tubular scaffolds had a conformation transition from random-coil conformation to Silk II conformation.

Abstract: Using genetic engineering methods, we attempted to produce novel silk-like proteins with new function by combining several functional sequences selected from fibroin of Bombyx mori (B.mori), Samia Cynthia ricini (S.c.ricini) and spider silks or by inducing cell adhesive sequence or calcium binding sequence into silk proteins. The secondary structure of these silk-like proteins was characterized with solid state NMR. Cell adhesion assay indicated that silk-like proteins have higher cell activity. Mineralization of fibroin protein was improved with induction of calcium binding sequence. Nanofiber formation of silk-like proteins was achieved using electrospinning. Fiber was formed from silk-like proteins. These silk-like proteins might be candidates to meet requirement in the field of biomaterials.

Abstract: Silk fibroin (SF) films containing 5wt% of CaCl2 were prepared by a cast-film method from the degummed SF and then immersed into the simulated body fluid (SBF) to deposit hydroxyapatite (HAp) crystals. The multilayer film of HAp and SF (5-layers), and pure SF film (4-layers) were prepared by a thermo-compression method at 130 °C and 3MPa for 4min. The ratio of β-sheet structure against other structures in both samples showed almost same value of 55.8% and 55.1%. The swelling ratio and in vitro biodegradation were examined by incubating in phosphate-buffered saline (PBS) with and without protease XIV for 1 to 14 days. The changes of sample weight and its tensile strength were investigated. The multilayer film showed slower biodegradation and higher mechanical strength compared with pure SF film.