Kobunshi - Vol. 58, No. 12 (December, 2009)

Hot Topics

Vol. 59, No. 1, January ( 2010)

Design of Bio-interfaces with Surface Topography using Self-Organization
Masaru TANAKA*, Mark BIRCH, Emiko ITO, Sadaaki YAMAMOTO, and Masatsugu SHIMOMURA
Graduate School of Science and Engineering, Department of Chemistry and Bioengineering, Yamagata University

The design of nano- and micro topographies based on self-organization has a variety of potential applications in tissue engineering scaffolds. We have reported a honeycomb- patterned film with regular interconnected pores that is formed by self-organization. In this study honeycomb films were prepared by poly(e-caprolactone) and assessed for their ability to support osteoblast adhesion, spreading and differentiation. The honeycomb films exerted a strong influence on cell morphology, proliferation, cytoskeleton, focal adhesion, and matrix production profiles. Quantification of bone formation reveals that the honeycomb films support greater production of matrix compared to flat control (M. Tanaka et al. JP Patent Pending 2008-137040). These early successes were achieved without the use of growth factors. These surfaces provide a reproducible tool to dissect the mechanistic basis for scaffold control of cell behavior and may also provide the basis for new therapeutic implants. Polymer Preprints, Japan 2009, 58, 2183.

High Refractive Index and Low Birefringence Cardo Polymer (OKP4)
Mitsuaki YAMADA
Osaka Gas Chemicals Co. Ltd.
Recently, the fields of audiovisual equipments such as mobile phone and digital camera, and liquid-crystal display have advanced rapidly, and subsequently also the need of new technical developments for optical materials are increasing. Fluorene moieties having cardo structure are used as optical materials because of their unique structures. Because the cardo structure has many aromatic cyclic groups, it offers a high refractive index. Furthermore, the fluorene cyclic group and the two aromatic cyclic groups have a twisted conformation, the anisotropy of the polarizability is minimal, and the birefringence is low. OKP4, which is one of the most typical cardo polymers, indicates a high refractive index and a low degree of birefringence, and therefore this polymer is ideal for optical lenses. Polymer Preprints, Japan 2009, 58, 2177.

Polymeric Micelle Carriers: A Promising Combination for MRI Contrast Agents and Anti-Cancer Drugs
Masayuki YOKOYAMA
Medical Engineering Laboratory, Jikei University School of Medicine
Polymeric micelles have been studied in the last two decades for targeting of anti-cancer drugs to solid tumors. Polymeric micelles can be formed through various cohesive interactions such as hydrophobic interactions and ionic interactions. Therefore, not only the anticancer drug targeting system, but also a tumor-selective MRI contrast agents can be prepared with Gd ion-containing polymeric micelles. These MRI contrast agents, which enhance image contrast by shortening T1 relaxation times of water, were successfully targeted to solid tumor sites, providing significant contrast increases in a mouse tumor model. The combination of the MRI diagnosis and the chemotherapy with the polymeric micelle carrier can greatly contribute to cancer treatments through selection of preferred patients for the polymeric micelle chemotherapy as well as through early diagnosis of tumor. Polymer Preprints, Japan 2009, 58, 2186.

Development of Small-Diameter Vascular Graft Made from Silk Fibroin
Tetsuo ASAKURA*, Michiko SATO and Yasumoto NAKAZAWA
Department of Biotechnology, Tokyo University of Agriculture and Technology
There is an increasing need for vascular grafts in the field of surgical revascularization. However, smaller vascular grafts made from synthetic biomaterials, particularly smaller than 5 mm in diameter, are associated with high incidence of thrombosis. Here, we evaluated the potential of silk fibroin to generate vascular prosthesis for small arteries. Silk fibroin-based grafts (1.5 mm in diameter, 10 mm in length) were implanted into the abdominal aorta of male 10 to 14-week-old Sprague Dawley rats by end-to-end anastomosis. Polytetrafluoroethylene (PTFE)-based grafts were used as control. Patency of the fibroin grafts at 1 year after implantation was significantly higher than that of PTFE grafts (85.1% vs. 30%, p< 0.01). Our findings demonstrate that a small-diameter silk fibroin-based vascular graft has excellent patency. Polymer Preprints, Japan 2009, 58, 3726.

Enzymatic Polymerization Enables Synthesis of Various Polysaccharides and Exhibits a Wide Spectrum of Enzyme Catalysis
Shiro KOBAYASHI
R & D Center for Bio-based Materials, Kyoto Institute of Technology
Hydrolase enzymes catalyzed polymerizations of appropriately designed monomers to afford perfectly structure-controlled natural and unnatural polysaccharides for the first time. In all polymerizations, the enzyme catalyzed the bond-formation reaction in vitro to produce polymers, which is a reverse reaction of the inherent enzyme catalysis in vivo to break the bond of a substrate via hydrolysis. Typically, fluoride-type monomers gave cellulose and xylan via polycondensation, and oxazoline-type monomers produced chitin, hyaluronan, chondroitin, etc via ring-opening polyaddition. Hybrid-polysaccharides were also synthesized similarly. Hyaluronidase enzyme interestingly showed a wide spectrum of enzymatic catalysis, i.e., supercatalysis (see Figure), that is far beyond the key and lock theory of normal enzymatic catalysis. For the monomer design and the reaction mechanism, a new concept of "transition-state analogue substrate" (TSAS) has been proposed. This enzymatic polymerization attracts attention from a viewpoint of "green polymer chemistry". Polymer Preprints, Japan 2009, 58, 4985.

Coordination Programming of Superior Conductive Molecular Wires
Hiroshi NISHIHARA
School of Science, The University of Tokyo
Surface-immobilized p-conjugated redox-active metal complex oligomer wires were synthesized using stepwise coordination reactions of metal ions and bis-terpyridine bridging ligands. This method is useful to prepare molecular wires in one to three dimensions with the desired sequence and number of different unit structures. In these molecular wire films, electron conduction occurs by the successive electron hopping between neighboring redox sites within a molecular wire. The p-conjugated redox complex molecular wires show the superior long-range electron-transport ability. The bd value, indicating the degree of decrease in the electron-transfer rate constant with distance along the molecular wire between the electrode and the redox active species at the terminal of the wire, was 0.002 A-1 for molecular wires of cobalt complex oligomers. Polymer Preprints, Japan 2009, 58, 2831.