| POLYMERS Vol.65 No.6 |
| >> Japanese | >> English |
COVER STORY
Painless Polymers: Why so Friendly? |
| COVER STORY: Highlight Reviews |
| Mechanism of Biocompatibility on 2-Methacryloyloxyethyl Phosphorylcholine Polymer Surfaces | Kazuhiko ISHIHARA |
| <Abstract> Many kinds of artificial organs and medical devices are utilized for treatment of disease. They are playing a very important role to save the life of humans. However, the use of these medical devices for long term induces foreign body reactions as immunoresponse from a living organism, and that can lead to severe problems. Thus, fully biocompatible materials are needed to conduct safer medical treatment with the medical devices. We focus on bioanalogous cell membrane structure, using polymer materials with phospholipid polar groups that are designed by inspiration from the natural cell membrane structure. The phospholipid polymers show inhibition of bioresponse including cell adhesion and activation. The latter is due to the unique characteristics of the phospholipid polar group. Here, the mechanism of biocompatibility observed on the phospholipid polymer surfaces will be explained with attention to the water structure surrounding the polymers. Keywords: Biocompatibility / Phosphorylcholine Group / Hydration / Protein Adsorption Resistance / Artigicial Organs |
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| Chain Conformation of PEG in Water | Seigou KAWAGUCHI |
| <Abstract> Polyethylene glycol (PEG) is a represetative linear water soluble and amphiphilic polymer. It dissolves not only in a large number of organic solvents but also in water. Nowadays, PEG is also a represetative bio-philic, bio-compatible, and bio-friendly polymer and widely used in the living body fields. In this short review, the molecular conformation of PEG chain in water was surveyed. Static light scattering and viscometric measurements for PEG’s having Mw ranged from 62 to 1.1×107 were studied. Mw-dependence of mean-squared radius of gyration and intrinsic viscosity was analyzed by the wormlike chain model to determine the chain stiffness parameter. PEG chain was found to behave as a typical flexible polymer with chain stiffness parameter of 1.1 nm in water at 25 ℃. Two feasible explanations why PEG chain acts as a bio-friendly polymer in water are proposed from a standpoint of the polymer solution research. Keywords: PEG/ Polymer Conformation / Water Soluble Polymer / Light Scattering / Intrinsic Viscosity / Persistence Length / Wormlike Chain / Bio-compatible |
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| COVER STORY: Topics and Products |
| Application for Theranostics of Amphiphilic Polysarcosine-Block-Polylactic Acid Copolymers | Eiichi OZEKI |
| <Abstract> The nanoparticle “Lactosome” is a polymeric micelle formed by self-assembly of biodegradable amphiphilic block copolymer composed of poly(sarcosine), which is a hydrophilic chain and poly(L-lactic acid), which is a hydrophobic chain. The Lactosome is hardly recognized by the self-defense system of living organisms like the reticuloendothelial system. Lactosome was found to be stable in blood circulation, and gradually accumulated specifically at a tumor site, which is due to the enhanced permeation and retention (EPR) effect. In this paper, we introduce Theranostics (fusion of molecular imaging and drug delivery system) with using Lactosome for cancer treatment. Keywords: Polysarcosine / Theranostics / Amphiphilic Polymer / Enhanced Permeation and Retention Effect(EPR Effect) / Stealth Effect / Photodynamic Therapy(PDT) / Internal Radiation Therapy / Drug Delivery System (DDS) |
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| Hysteresis in the Phase Separation of Aqueous Poly(2-Isopropyl-2-Oxazoline) Solution | Yukiteru KATSUMOTO |
| <Abstract> Aqueous solutions of amphiphilic polymers often undergo a lower critical solution temperature (LCST) phase transition. In the case of aqueous poly(2-isopropyl-2-oxazoline) (PiPrOx) solutions, the phase separation is followed, upon prolonged heat treatment, by an irreversible crystallization of the polymer. Infrared spectroscopy combined with molecular orbital (MO) calculations and spectral measurements with model compounds were employed to monitor water/polymer interactions and changes in polymer conformation during the LCST-type phase separation. The thermally induced spectral variations suggest that the dehydration of the PiPrOx amide function occurs gradually as the temperature is raised from 20 ℃ up to the cloud point (Tc). Upon prolonged heating of the phase separated mixture at constant temperature (Tc + ～2 ℃), the infrared spectrum of the polymer undergoes further changes ascribed to conformational transitions of the polymer backbone. These changes, which are irreversible upon cooling the solution below Tc, lead to the conformation taken by the polymer in the crystalline phase. Keywords: Poly(2-Isopropyl-2-Oxazoline) / Aqueous Solution / Phase Separation / Hysteresis / Infrared Spectroscopy / Molecular Orbital Calculation |
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| Polyethylene Glycol Derivatives for DDS Market | Yuji YAMAMOTO |
| <Abstract> Polyethylene glycol (PEG) is one of most widely used synthetic polymers for medical use, since PEG is FDA approval biocompatible polymer showing low toxicity and low immunogenicity. Especially in the field of drug delivery system (DDS), functionalized PEG, which has functional groups at the end groups, is used in a great number of drug formulations and devices such as PEGylated proteins, hydrogels and polymer micelles. On the other hand, chemical properties and stability of PEG are also great advantages to introduce of a variety of functional groups by severe specifications to be used in medical use. In this article, production and application of PEG is described mainly from the view point of Manufacturer of PEG. Keywords: Biomaterial / Polyethylene Glycol / PEG / Drug Delivery System |
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| Polymer Science and I: A Personal Account |
| Designer | Takaya TERASHIMA |
| <Abstract> I am a designer to create functional polymeric materials on the basis of my curiousity and ideas. Though the recent position is distinct from a car designer of my childhood dream, I could eventually contribute to the car manufacturing as a polymer designer with innovative materials. |
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| Front-Line Polymer Science |
| Dynamic Morphology Conversion of Molecular Assemblies through Membrane Fusion and Fission | Shunsaku KIMURA |
| <Abstract> Membrane fusion and fission are common phenomena observed with various types of cells as described about excretion of exosome, endosome, and caveola from cell membranes, which play an essential role of communications in the biological events. The molecular mechanisms of these biological systems are currently on the way to clarification, but studies on the morphology conversions with use of model systems lag far behind. The present short review focuses on morphology conversion of molecular assemblies with taking examples of vesicle fission from planar sheet, nanotube fusion into planar sheet, fusion of nanosheet with nanotube followed by vesicle fission, and others. In most cases, amphiphilic block polypeptides having a hydrophobic helical block were used. All the morphology conversions are explainable in terms of helical peptide association controlled by helix length, stereo-chemistry, dipole, ridge-groove fit between helix surfaces, and steric effect of the hydrophilic block. One of the perspectives of morphology conversion will be application for a communication tool between two or more systems. Keywords: Molecular Assembly / Vesicle / Nanotube / Membrane Fusion / Membrane Fission / Peptide Assembly / Morphology Conversion / Chimeric Morphology / Autopoiesis |
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