Papers by Author: Koji Abe

Abstract: Larval silk/cement proteins from a caddisfly, Stenopsyche marmorata, were isolated as a protein mixture of Smsp-1, 2, 3 and 4. Smsp-1 is a giant phosphorylated protein, which occupies ca. 45%-mass of the silk gland content, and composed of a long-range periodic amino acid sequences, involving 8 kinds of characteristic segments. The silk protein film was prepared and drawn in water up to 9-folds of the initial axis length, then the drawn film was subjected to polarized FT-IR and WAXD. The results implied that the Smsp-1 backbone adopts two different conformations, one of which was the β-turn-like conformers. The molecular mechanic studies were separately performed to evaluate the solid-state chain structures of the hydrophobic/Pro-rich segments 3 and 4, which are enriched in the primary sequence of Smsp-1, and the results were coincident with those from the vibration spectra and WAXD. The molecular dynamic (MD) studies were also carried out in order to estimate their preferred chain conformations in a solution state. The MD trajectory suggests that the segments 3 and 4 tend to adopt a turn-like conformation, which is a potential precursor of the β-turn-like conformers. In conclusion, the underwater silk proteins have a fiber-forming mechanism, which is substantially different from a silkworm, Bombyx mori.

Abstract: Natural bone is a composite mainly made from nano/micro-structure of hydroxyapatite and collagen fibers. For bone regeneration by tissue engineering, it is important to synthesize three dimension nano-composites with good biocompatibility, high bioactivity and great bonding property as potentially useful scaffold. In this study, we fabricated chitosan nano-nonwoven scaffold via electrospinning and modified chitosan scaffolds by carboxymethylation (CM) to improve the osteoconductive characteristics. Results of FTIR confirmed the existence of carboxymethyl groups of CMChitosan. Moreover by employed mice osteoblast (MC3T3-E1) cell for adhesion, proliferation and differentiation assays, we found that CMChitosan appeared to have effect on the late stages of osteoblast behavior (calcium deposit).

Abstract: Functional scaffolds fabricated from biopolymers are of great importance for tissue engineering. In this paper, by mimicking the combination of two major components in Extracellular Matrix – collagen and polysaccharide respectively, we fabricated gelatin and chitosan hybrid sponge for cartilage tissue engineering. Extending previous results of gelatin/chitosan film showed that all the hybrid coating film (chitosan: gelatin= 4:1; 1:1; 1:4) can support the adhesion of ATDC5 that comparable to Tissue Culture Dish (TCD). More importantly, stem cell line ATDC5 on coating dish of chitosan: gelatin=1:4 showed enhanced differentiation rate than that on other films and TCD. For three dimensional scaffolds, we fabricated hybrid sponge scaffold of chitosan: gelatin=4:1, 2:1, 1:1, 1:2, 1:4 respectively. Morphological characterizations of the sponges showed that this kind of gelatin/chitosan hybrid scaffold is promising for application in cartilage tissue engineering.

Abstract: Natural bone is a composite mainly made from nano/micro-structure of hydroxyapatite and collagen fibers. For bone regeneration by tissue engineering, it is important to synthesize nano-composites with good biocompatibility, high bioactivity and great bonding property as potentially useful scaffold. In this study, we fabricated chitosan nano-nonwoven scaffold via electrospinning and modified chitosan scaffolds by carboxymethylation (CM). Moreover scaffolds were macerated in SBF (simulated body fluid) to form hydroxyapatite on its surface. Surface morphologies (SEM) showed that nano/micro particles formed on the surface of the carboxymethyl chitosan fibrous scaffold. Results of FT-IR and XRD confirmed that the nano/micro particles were hydroxyapatite crystalline. Moreover by employed mice osteoblast (MC3T3-E1) cell for adhesion, proliferation and differentiation assays, and the hydroxyapatite particles appeared to have a great effect on the late stages of osteoblast behavior (alkaline phosphatase ).

Abstract: Ti and Ti alloys are widely used as metallic implants, because of their good mechanical properties and nontoxic behavior. However, they have problems as the implant-materials, namely, high Young’s modulus comparing that of bone and low bonding ability with bone. There is a need to develop the Ti and Ti alloys with lower Young’s modulus and good bonding ability. In previous study, Ti composite containing biodegradable poly-L-lactic-acid (PLLA) fiber has been fabricated to improve these problems. However, this composite has low strength because of the imperfect sintering of Ti matrix. To improve its strength, sintering of Ti matrix should be completed. In this study, Ti-NaCl composite material was fabricated by spark plasma sintering (SPS) method using powder mixture of Ti and NaCl to complete the sintering of Ti matrix. To obtain porous Ti samples, Ti-NaCl composite were put into hot water of 100 oC. The porous Ti was dipped into PLLA melt in order to introduce PLLA into the pores of porous Ti. Finally, Ti-PLLA composite was obtained, and PLLA plays a role as reinforcement of Ti matrix. It was found that the Ti-PLLA composite has gradient structure and mechanical properties.