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  • 1
    Electronic Resource
    Electronic Resource
    Hydrogel microspheres III. Temperature-dependent adsorption of proteins on poly-N-isopropylacrylamide hydrogel microspheres (1992)
    Springer
    Colloid & polymer science 270 (1992), S. 53-57 
    Details
    ISSN: 1435-1536
    Keywords: Hydrogel ; thermosensitivity ; protein ; adsorption and desorption ; hydrophilicity ; microsphere
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Precipitation polymerization of N-isopropylacrylamide (NIPAM) with methylenebisacrylamide (MBAAm) in water at 70°C gave thermosensitive hydrogel microspheres. The adsorbability of proteins on the poly-NIPAM microspheres was found to depend on temperature. Below the lower critical solution temperature (LCST) of poly-NIPAM in an aqueous medium, that is, around 32°C, the microspheres hold a large amount of water inside and their surface is hydrophilic enough to suppress the adsorption of proteins. On the contrary, above 32°C, the micropheres deswell and their surface becomes hydrophobic and, consequently, susceptible to adsorption of a large amount of proteins. Proteins once adsorbed on the microspheres at a high temperature could be desorbed more or less by lowering the temperature to below 32°C. The extent of desorption at low temperatures was found to depend on the incubation time for adsorption at high temperatures.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00656929
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  • 2
    Electronic Resource
    Electronic Resource
    Ozone-induced graft polymerization onto polymer surface (1993)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 31 (1993), S. 1035-1043 
    Details
    ISSN: 0887-624X
    Keywords: ozone oxidation ; graft polymerization ; peroxide ; protein adsorption ; cell adhesion ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Ozone-induced graft polymerization was carried out to improve polymer surfaces. The polymers were exposed to ozone and the surface density of peroxides formed was determined by three methods; iodide, DPPH, and peroxidase method. The peroxide production could be readily controlled by the ozone concentration and the ozone exposure time. In addition, it was dependent on the kind of polymer. Further, it seemed probable that the ozone oxidation introduced peroxides not only on the outermost surface but also into a layer deeper from the outermost surface. Such polymeric peroxides were capable of initiating graft polymerization onto PU. All the physical and biological measurements on the grafted surface indicated that ozone-induced graft polymerization has effectively made the PU surface covered with the grafted water-soluble chains, their location being restricted to the film surface region. The interaction of the PU surface with blood components could be greatly reduced by the surface graft polymerization. © 1993 John Wiley & Sons, Inc.
    Additional Material: 13 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pola.1993.080310426
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  • 3
    Electronic Resource
    Electronic Resource
    Chemical properties of water-soluble, nonionic azo compounds as initiators for emulsion polymerization (1996)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 34 (1996), S. 1237-1243 
    Details
    ISSN: 0887-624X
    Keywords: water-soluble nonionic initiator ; azo compound ; initiator efficiency ; cage effect ; emulsion polymerization ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Four kinds of water-soluble, nonionic azo compounds were studied in terms of their decomposition rate and initiator efficiency in radical polymerization, and then used for emulsion polymerization. They had relatively low initiator efficiency from 0.09 to 0.46. It was attributed to the susceptibility to a cage effect, depending on their molecular size and hydrophobicity. Four azo compounds initiated emulsion polymerization but nonionic latex particles were not obtained unexpectedly. Methanol-containing medium results in the formation of a bimodal particle size distribution as well as a bimodal molecular weight distribution. © 1996 John Wiley & Sons, Inc.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Interactions between temperature-sensitive hydrogel microspheres and granulocytes (1995)
    New York, NY : Wiley-Blackwell
    Polymers for Advanced Technologies 6 (1995), S. 534-540 
    Details
    ISSN: 1042-7147
    Keywords: poly(N-isopropylacrylamide) ; hydrogel ; microsphere ; granulocyte ; cell activation ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Poly(N-isopropylacrylamide) (PNIPAM) has a low critical solution temperature (LCST) at 32°C in water and the hydrophilicity changes through the LCST. The microspheres whose surface was composed of PNIPAM exhibited phase transition behavior around 32°C. Therefore, the interactions between PNIPAM micropheres and granulocytes depended on the temperature. That is, the oxygen consumption and active oxygen production by cells in contact with PNIPAM-containing microspheres and adhesion of the microspheres to the cell surface were more enhanced above the LCST of PNIPAM than below it, whereas no significant temperature dependence of cell-microspheres interaction was observed in nonthermosensitive microsphere systems. It was suggested that the function of cells could be controlled with temperature using the temperature-sensitive microspheres.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pat.1995.220060715
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  • 5
    Electronic Resource
    Electronic Resource
    Porous polyurethane tubes as vascular graft (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Biomaterials 4 (1993), S. 347-354 
    Details
    ISSN: 1045-4861
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: A vascular graft with the inner diameter of about 3 mm was prepared from segmented poly (ether urethane) with an extrusion technique. To make the wall of the vascular grafts porous, NaCl salts were added to the polyurethane solution to be extruded and removed with water extraction after evaporating the solvent in the extruded tube. The wall was reinforced with elastic fiber to prevent dilation. The compliance of the vascular graft measured with the method of Hayashi et al. ranged from 0.2 to 0.3% mmHg-1. The initial Young's modulus was close to that of canine carotic artery, to which the porous polyurethane graft 4-cm long was anastomosed. Vascular grafts were occluded within 2 weeks after implantation, when their pore size was 0, 1.7, or 4.4 m̈m, whereas those with the pore size of 5.5, 7.4, and 30 m̈m were patent for longer than 4 weeks. When the vascular graft with the pore size of 30 m̈m was implanted for 6 months, the luminal surface was covered with neointima, but the endothelium-like cells appearing in the middle of the intima of the vascular graft were immature and sometimes had a very big nucleus. In addition, spindle-shaped, modified smooth muscle cells were noticed in the deep layer of the neointima, especially in the tissue where anastomotic intimal hyperplasia occurred. © 1993 John Wiley & Sons, Inc.
    Additional Material: 13 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jab.770040409
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  • 6
    Electronic Resource
    Electronic Resource
    Activation of human neutrophils by Arg-Gly-Asp-Ser immobilized on microspheres (1994)
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 28 (1994), S. 397-404 
    Details
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: The adhesive interaction of cells with extracellular matrix components is essential for a variety of cellular functions, and is frequently mediated by a tetra peptide, Arg-Gly-Asp-Ser (RGDS), located within fibronectin and other proteins. In this study, the RGDS-mediated activation of polymorphonuclear leukocytes accompanied by phagocytosis was investigated using monodisperse polymeric microspheres carrying RGDS. The parent and Arg-Gly-Glu-Ser (RGES)-carrying microspheres, which have no adhesion activity, were employed as controls. The ingestion of microspheres into PMN was not enhanced by immobilizing RGDS. However, PMNs exhibited unique oxygen consumption and enhanced liberation of reactive oxygen when RGDS-carrying microspheres were phagocytosed. These PMN responses disappeared with the addition of soluble RGDS. Furthermore, cytochalasin D, which inhibits actin polymerization, showed a marked inhibitory effect on oxygen consumption in the RGDS-carrying microsphere system, as compared with those in other systems. These findings show that RGDS-carrying microspheres induced the biospecific activation of PMNs by the signal transduction via RGDS-integrin binding without alteration in the degree of phagocytosis. © 1994 John Wiley & Sons, Inc.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jbm.820280315
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  • 7
    Electronic Resource
    Electronic Resource
    Protein adsorption and platelet adhesion onto polyurethane grafted with methoxy-poly(ethylene glycol) methacrylate by plasma technique (1993)
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 27 (1993), S. 1559-1567 
    Details
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Graft polymerization of methoxy-poly(ethylene glycol) methacrylate, an ester of methacrylic acid and monomethoxy-poly(ethylene glycol) (PEO), was performed onto a polyetherurethane (PU) film and tube under different polymerization conditions by a plasma treatment technique. The surface of grafted PU film was characterized by staining with dye, x-ray photoelectron spectroscopy, contact angle, and zeta potential. All these measurements indicated that water-soluble chains were immobilized on the PU surface, their location being restricted to the film surface region. The PU surface showed reduced protein adsorption in vitro and reduced platelet adhesion in vitro and ex vivo. The optimum graft density suppressing the protein adsorption was as low as 5 μg cm-2. When a small amount of dimethacrylate was added to the monomer solution for graft polymerization to introduce crosslinking in the grafted layer, protein adsorption was further slightly reduced. The extent of reduction in serum albumin adsorption was always less than that of γ-globulin. Although platelet adhesion was largely reduced by the surface graft polymerization, a definite amount of protein was always adsorbed to the grafted surface. © 1993 John Wiley & Sons, Inc.
    Additional Material: 15 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jbm.820271213
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  • 8
    Electronic Resource
    Electronic Resource
    Platelet deposition onto polymeric surfaces during shunting (1993)
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 27 (1993), S. 335-343 
    Details
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: In an attempt to develop blood-contacting tubes that can be applied for short-term uses with a reduced heparin concentration or, ideally, without heparinization, we evaluated the blood compatibility of polymeric materials with a rabbit ex vivo shunt model. The shunt tubes employed were made of silicone, plasticized poly(vinyl chloride) (PVC), and segmented poly(ether urethane) (PU). In addition, two kinds of surface-modified tube were used: poly(vinyl alcohol) (PVA)-coated PVC and poly(dimethylacrylamide) (PDMAA)-grafted PU. The ex vivo shunt results correlated well with protein adsorption and platelet adhesion in vitro. The following order for the extent of platelet deposition was given, irrespective of the blood-contacting duration: PDMAA-grafted PU 〈 PVA-coated PVC 〈 PU 〈 silicone, PVC. It is likely that many platelet aggregates detached from the PVA-coated PVC surface. For PDMAA-grafted PU, no trace of detachment of aggregates could be detected on any of the SEM photographs. The number and morphology of blood cells adhered onto the tube surfaces during ex vivo shunting were dependent on the kind of polymer surfaces, the blood exposure time, and the flow rate of blood. © 1993 John Wiley & Sons, Inc.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jbm.820270307
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  • 9
    Electronic Resource
    Electronic Resource
    Ex vivo and in vivo evaluation of the blood compatibility of surface-modified polyurethane catheters (1997)
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 35 (1997), S. 255-264 
    Details
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Catheter model tubes were prepared from a medical-grade polyetherurethane and their outer surfaces modified by surface-graft polymerization of acrylamide and dimethyl acrylamide (DMAA). The surface-graft layer was characterized by means of dry staining, scanning electron microscopy (SEM), X-ray photoelectron spectroscopy, and protein adsorption. Ex vivo evaluation for the blood compatibility of the surface-modified polyurethane was carried out using the polyurethane tube as an arterio-venous shunt between the carotid artery and the jugular vein of rabbits. When the surface density of grafted polymer was in the range of 10-30 μg/cm2, the in vitro adsorption of IgG exhibited a minimum value and platelet adhesion to the grafted polyurethane surface was insignificant, in marked contrast with that to the virgin (nonmodified) surface. The in vivo blood compatibility of polyurethane was evaluated by implanting the catheter tube in the inferior vena cava of rabbits from the femoral vein after ligation of a distal site of the exposed femoral vein. After remaining there for predetermined periods of time, the implanted catheters were taken out together with the veins of the rabbits that had been heparinized and sacrificed just prior to excision of the veins. After exchange of the blood in the veins for saline, the excised veins were opened by cutting longitudinally to inspect for clot formations on the surfaces of the implanted catheters. Occlusion of the inferior vena cava was not observed for any of the catheters, nor was there any apparent damage or microembolizations in the lungs and kidneys. Many small-sized clots were observed on the surfaces of the nonmodified polyurethane tubes after a 2-week implantation whereas the catheter surfaces grafted with DMAA polymer chains had a much smaller number of clots. When the blood compatibility of polyurethane surfaces was graded for relative evaluation from one (marked clotting) to five (no clotting) based on the size and number of the clots, the evaluation results were as follows: 3.1 (virgin, 2 weeks), 4.0 (grafted, 1 week), 4.1 (grafted, 2 weeks), and 3.5 (grafted, 1 month). © 1997 John Wiley & Sons, Inc.
    Additional Material: 9 Ill.
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  • 10
    Electronic Resource
    Electronic Resource
    Preparation and structural characteristics of stimuli-responsive hydrogel microspherePoster presented at the “International Symposium on Advanced Network-Polymer, Kansai University” (ISANKU), at Kansai University, Suita, Osaka, Japan, on December 5-6, 1995. (1996)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 240 (1996), S. 187-196 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Monodisperse hydrogel microspheres were prepared by precipitation polymerization from acrylamide (AAm), methylenebisacrylamide (MBAAm) and methacrylic acid (MAc) in ethanol, and examined their stimuli response by changing pH or temperature. The microsphere was found to contract continuously by heating. The microsphere with a lower-content MBAAm exhibit more pronounced heat-contraction. Also at low pH the microsphere contracted due to the protonation of the carboxyl group in MAc. The internal structure was observed by small angle X-ray scattering (SAXS) and the stimuli-response mechanism was discussed from the view of network chain conformation.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1996.052400117
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