Browsing by Author "Yoshida, Y"

Now showing 1 - 3 of 3
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    Chemical modification of poly(vinyl chloride) resin using poly(ethylene glycol) to improve blood compatibility
    (BIOMATERIALS, 2005)
    Poly(vinyl chloride) (PVC) was aminated by treating the resin with a concentrated aqueous solution of ethylenediamine. The aminated PVC was then reacted with hexamethylene diisocyanate to incorporate the isocyanate group onto the polymer backbone. The isocyanated PVC was further reacted with poly(ethylene glycol) (PEG) of molecular weight 600 Da. The modified polymer was characterized using infrared and X-ray photoelectron spectroscopy (XPS) and thermal analysis. Infrared and XPS spectra showed the incorporation of PEG onto PVC. The thermal stability of the modified polymer was found to be lowered by the incorporation of PEG. Contact angle measurements on the surface of polymer films cast from a tetrahydrofuran solution of the polymer demonstrated that the modified polymer gave rise to a significantly hydrophilic surface compared to unmodified PVC. The solid/water interfacial free energy of the modified surface was 3.9 ergs/cm(2) as opposed to 18.4ergs/cm(2) for bare PVC surface. Static platelet adhesion studies using platelet-rich plasma showed significantly reduced platelet adhesion on the surface of the modified polymer compared to control PVC. The surface hydrophilicity of the films was remarkably retained even in the presence of up to 30 wt % concentration of the plasticizer di-(2-ethylhexyl phthalate). The study showed that bulk modification of PVC with PEG using appropriate chemistry can give rise to a polymer that possesses the anti-fouling property of PEG and such bulk modifications are less cumbersome compared to surface modifications on the finished product to impart anti-fouling properties to the PVC surface. (C) 2004 Elsevier Ltd. All rights reserved.
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    In vitro evaluation of antioxidant defense mechanism and hemocompatibility of mauran
    (CARBOHYDRATE POLYMERS, 2013) Raveendran, S; Palaninathan, V; Chauhan, N; Sakamoto, Y; Yoshida, Y; Maekawa, T; Mohanan, PV; Kumar, DS
    Mauran (MR), a highly polyanionic sulfated exopolysaccharide was extracted from moderately halophilic bacterium; Halomonas maura and characterized using X-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy. Purified MR was evaluated for antioxidant defense mechanisms under in vitro conditions using L929, mouse fibroblast cell line and mice liver homogenate. It was demonstrated that MR could impart protective effect against oxidative stress in both cells and tissue up to a concentration of 500 mu g, which is found to be safe under laboratory conditions. Various enzymatic and non-enzymatic parameters of antioxidant mechanisms were evaluated and concluded that MR has the tendency to maintain a balance of antioxidative enzymes with in the test systems studied. Also, hemocompatibility assay performed revealed that MR has a lesser hemolytic index and exhibited a prolonged clotting time, which shows both antihemolytic, and antithrombogenic nature respectively. Furthermore, absorption studies performed using fluorescent-labeled MR confirmed that MR accumulated within the cell cytoplasm neither induced cellular lysis nor affected the cell integrity. (C) 2013 Elsevier Ltd. All rights reserved.
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    Surface modification of poly( ethylene terephthalate) by plasma polymerization of poly( ethylene glycol)
    (JOURNAL OF MATERIALS SCIENCE-MATERIALS IN MEDICINE, 2007) Kumar, DS; Fujioka, M; Asano, K; Shoji, A; Jayakrishnan, A; Yoshida, Y
    Poly( ethylene glycol) ( PEG) was 'polymerized' onto poly( ethylene terephthalate) ( PET) surface by radio frequency (RF) plasma polymerization of PEG ( average molecular weight 200 Da) at a monomer vapour partial pressure of 10 Pa. Thin films strongly adherent onto PET could be produced by this method. The modified surface was characterized by infra red (IR) spectroscopy, scanning electron microscopy (SEM), atomic force microscopy (AFM), cross-cut test, contact angle measurements and static platelet adhesion studies. The modified surface, believed to be extensively cross-linked, however showed all the chemical characteristics of PEG. The surface was found to be highly hydrophilic as evidenced by an interfacial free energy of about 0.7 dynes/cm. AFM studies showed that the surface of the modified PET became smooth by the plasma polymerized deposition. Static platelet adhesion studies using platelet rich plasma (PRP) showed considerably reduced adhesion of platelets onto the modified surface by SEM. Plasma 'polymerization' of a polymer such as PEG onto substrates may be a novel and interesting strategy to prepare PEG-like surfaces on a variety of substrates since the technique allows the formation of thin, pin-hole free, strongly adherent films on a variety of substrates.