Papers by Author: Tetsuya Tateishi

Abstract: Linear and Star-shaped PCL-b-PEG copolymers were synthesized through a two step process, including the first step to synthesize the star-shaped PCL through ring-opening polymerization of Γ-caprolactone initiated from multi-functional alcohol under the existence of tin(II) ethylhexanoate [Sn(Oct)2] catalyst, and the following step to couple the obtained star-shaped PCL with PEG segments using bi-functional linker. The structure of the polymers was confirmed by IR, NMR, GPC, et al. The aggregation behaviors of the star-shape copolymers were compared with that of the linear block copolymer with corresponding molecular weight of each arm, and the influences of structure factors were discussed.

Abstract: A biocompatible glue consisting of human serum albumin (HSA) and citric acid derivative (CAD), named CAD-A glue was developed. CAD was successfully synthesized by the reaction between citric acid and N-hydroxysuccinimide in the presence of 1-ethyl-3-(3-dimethyl aminopropyl) carbodiimide hydrochloride. When the CAD-A glue was applied to the collagenbased casings, it took 7 min to obtain half of maximum bonding strength (760 g/cm2). The bonding strength of this glue to collagen-based casings increased with increasing of HSA concentration.The bonding strength of CAD-A glue increased with increasing CAD concentration up to 200 mM, and then decreased with increasing CAD concentration under the fixed HSA concentration (50 w/w%). The CAD-A glue showed excellent wound closure ability rather than fibrin glue when applied to the mouse skin. These results suggested that this developed glue had both tissue compatibility and bonding strength for use in clinical field.

Abstract: In this study, three kinds of photo-reactive polymers, namely positively charged azidophenyl-derived polyallylamine (AzPhPAAm), negatively charged azidophenyl-derived poly(acrylic acid) (AzPhPAAc) and neutral azidophenyl-derived poly(ethylene glycol) (AzPhPEG), were synthesized by introduction of photo-reactive group (-N3) into polyallylamine, poly(acrylic acid) and poly(ethylene glycol), respectively. The structure of the azidophenyl-derived polymers was confirmed by 1H-NMR measurement. All of the photo-reactive polymers can be pattern-grafted on the surface of cells culture plate, which was confirmed by the optical microscopy observation. The contact angle decreased after surface modification by the photo-reactive polymers. Human mesenchymal stem cells (MSC) cultured on the modified surfaces showed different morphology. The cells adhered and spread more on the PAAm- and PAAc-grafted surfaces than on the PEG-grafted surface. The pellets formed on PAAm- and PEG-grafted surfaces in condrogenic differentiation medium were positively stained by safranin O/ fast green. But the pellet formed on PAAc-grafted surface did not show obviously positive staining for safranin O/ fast green. These results indicate that the PAAm- and PEG-grafted surfaces promoted chondrogenic differentiation of MSC.

Abstract: A novel collagen sponge that can protect cell leakage during cell seeding was developed by wrapping all the surfaces except the upside of a collagen sponge with membrane that has pores smaller than cell. The collagen sponge was used for three-dimensional culture of human bone marrow-derived mesenchymal stem cells (MSCs). The cells adhered to the collagen, and proliferated to fill the spaces in the sponge. The cell seeding efficiency was higher than 95%. The MSCs cultured in the collagen sponge in the chondrogenic induction medium supplemented with TGF-β3 and BMP6 expressed genes encoding type II collagen, SOX9 and aggrecan. HE staining indicated the round morphology of differentiated cells and the extracelluler matrices were positively stained by safranin O and toluidine blue. Type II collagen and cartilage proteoglycan were detected by immunostaining with anti-type II collagen and anti-cartilage proteoglycan. These results suggest the chondrogenic differentiation of MSCs. The collagen sponge facilitated cell seeding and chondrogenic differentiation of MSCs, and will be useful for cartilage tissue engineering.

Abstract: Three-dimensional biodegradable porous scaffolds play an important role in tissue engineering as temporary templates for transplanted cells to guide the formation of the new organs. Two kinds of novel biodegradable porous scaffolds for tissue engineering have been developed by our group by hybridizing synthetic poly(α-hydroxy acids) with naturally derived collagen. One is their hybrid sponge prepared by introducing collagen microsponges in the pores of poly(α-hydroxy acids) sponge. The other one is their hybrid mesh prepared by forming collagen microsponges in the interstices of poly(α-hydroxy acids) mesh. The hybrid scaffolds were used for three-dimensional culture of fibroblast, tenocytes, chondrocytes and mesenchymal stem cells for tissue engineering of skin, ligament, cartilage and osteochondral tissue. These cells adhered and spread well in the hybrid scaffolds, proliferated, secreted extracellular matrices and formed the respective tissues. The synthetic polymer sponge, or mesh serving as a skeleton, reinforced the hybrid scaffolds and resulted in easy handling, while the collagen microsponges provided the hybrid sacffolds with a microporous structure and hydrophilicity, and therefore, easy cell seeding. The hybrid scaffolds will be useful for tissue engineering.

Abstract: Micropatterned PEGylated substrates with two-dimensional arrays of plasma-etched circular domains (diameter:100 micro-m) were prepared by coating of mercapto-functionalized poly(ethylene glycol) (PEG) on Au surface, followed by plasma-etching through a metal mask pattern with circular holes. The PEGylated region on the patterned substrate works to repel proteins, consequently, inhibits cell adhesion. Then the micro-patterning of bovine articular chondrocytes or rat primary hepatocytes hetero-spheroids underlaid with human umbilical endothelial cells (HUVEC) was achieved on the plasma-etched circular domains, exposing the base gold surface. Obtained results suggested that the efficiency of inhibiting non-specific protein adsorption significantly affects on construction of micro-patterned cell adhesion and hetero-spheroids. The formation of hetero-spheroid thus suggested is significantly modulated by suface properties, particularly non-fouling character of PEG region. These arrayed spheroids is promising materials for tissue and cell-based biosensors (TBB/CBB) as well as tissue engineering technologies.

Abstract: Polyamides containing amino acid residues were synthesized through a chemoenzymatic route. At first, monomers containing amino acid esters at both ends were prepared from amino acid esters and bifunctional acid chlorides through a Scotten-Baumann reaction under organic condition. Diamine was used as bifunctional nucleophilic reagent to aminolysis the amino acid ester bonds of these monomers under protease catalysts, leading to the polycondensation to form the desired polyamides containing amino acid residues. Spectra characterizations confirmed the structure of obtained polyamides. The factors that influence the polymerization, including the type of enzymes, the amount of enzymes, and the water contents in the solvent, were also discussed. It is expected that the obtained polyamides have the potential for biomaterial applications.

Abstract: A new method for the preparation of biodegradable porous scaffolds has been developed by using preprepared ice particulates as porogen material. A novel kind of hybrid biodegradable porous scaffold has been developed by forming collagen microsponges in the pores or interstices of a synthetic polymer sponge or mesh. A hybrid sponge of synthetic polymer, collagen and hydroxyapatite has been developed for hard tissue engineering. Bovine articular cartilage-like tissue has been engineered by culturing chondrocytes in the PLGA-collagen scaffolds.