Summary: Silk fibroin cast film was prepared using a ternary solvent system of CaCl2/CH3CH2OH/H2O (1/2/8 in mole ratio). A drying temperature at casting influenced crystal structure of fibroin. When a drying temperature was set lower than 9 °C, the cast film became amorphous. When a drying temperature was set higher than 40 °C, a fibroin film of silk‐II structure was obtained. In order to produce a fibroin film of silk‐I structure, a preferable temperature range was from 20 to 26 °C. The crystal transformation from random coil structure into silk‐I could be made through exposure of an amorphous film to water vapor. As for the crystal transformation from silk‐I into silk‐II, the treatment with a glycerin solution was effective. In the course of the treatment a film showed self‐thinning and self‐expanding. The expansion ratio exceeded 40% at maximum. The film produced accompanying self‐expansion was ductile in nature.The apparent self‐expansion percentage as a function of initial thickness of the film. The ductility of the film was classified into four stages from the observation of recovery behavior after folding: •, very soft; ♦, soft; ▪, middle; ▴, hard (see Figure 5).imageThe apparent self‐expansion percentage as a function of initial thickness of the film. The ductility of the film was classified into four stages from the observation of recovery behavior after folding: •, very soft; ♦, soft; ▪, middle; ▴, hard (see Figure 5).

Interfacial interactions between calcined hydroxyapatite (HAp) nanocrystals and surface-modified substrates were investigated by measuring adsorption behavior and adhesion strength with a quartz crystal microbalance (QCM) and a contact-mode atomic force microscope (AFM), respectively. The goal was to develop better control of HAp-nanocrystal coatings on biomedical materials. HAp nanocrystals with rodlike or spherical morphology were prepared by a wet chemical process followed by calcination at 800 degrees C with an antisintering agent to prevent the formation of sintered polycrystals. The substrate surface was modified by chemical reaction with a low-molecular-weight compound, or graft polymerization with a functional monomer. QCM measurement showed that the rodlike HAp nanocrystals adsorbed preferentially onto anionic COOH-modified substrates compared to cationic NH2- or hydrophobic CH3-modified substrates. On the other hand, the spherical nanocrystals adsorbed onto NH2- and COOH-modified substrates, which indicates that the surface properties of the HAp nanocrystals determined their adsorption behavior. The adhesion strength, which was estimated from the force required to move the nanocrystal in contact-mode AFM, on a COOH-grafted substrate prepared by graft polymerization was almost 9 times larger than that on a COOH-modified substrate prepared by chemical reaction with a low-molecular-weight compound, indicating that the long-chain polymer grafted on the substrate mitigated the surface roughness mismatch between the nanocrystal and the substrate. The adhesion strength of the nanocrystal bonded covalently by the coupling reaction to a Si(OCH3)-grafted substrate prepared by graft polymerization was approximately 1.5 times larger than that when adsorbed on the COOH-grafted substrate.

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The hydrothermal treatment was applied to sericin and the hydrolysis behavior was investigated. The gel filtration chromatography revealed that sericin was hydrolyzed to di-or tri-peptide easily when the treatment was made at 200*. In addition, the hydrolyzate obtained showed an antioxidant activity against DPPH radicals.

Fresh hydroxyapatite(HAP) was prepared in an aqueous phase by mixing CaCl2 with K2HPO4 in the presence of dodecyl phosphate(DP) and arginine (Arg), where DP/Arg = 1/3 in molar ratio. Arg was added in order to enhance the solubility of DP. The degree of crystallinity of the HAP decreased with a concentration of DP, because DP was adsorbed to the growth sites on the nuclei through its terminal phosphate group as a crystal poison. The effect of adsorption of DP on a ripened HAP was also studied. Though polyethylene glycol p-isooctylphenyl ether (TX-100) was scarcely adsorbed on the raw surface of HAP, it was adsorbed after pretreatment of the surface with DP. This fact was explained in terms of surface modification by the adsorption of DP. Alkyl chains of DP protruding from the surface captured those of TX-100 through hydrophobic interaction on the surface. It was concluded that the phosphate group of DP plays an important role in regulation of the crystal growth and surface modification by virtue of isomorphous substitution of phosphate group of DP for phosphate ion on the surface of HAP.