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  • 1995-1999  (6)
  • Chemistry  (6)
  • 1
    Electronic Resource
    Electronic Resource
    Analysis of shear-dependent bacterial adhesion kinetics to biomaterial surfaces (1995)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 41 (1995), S. 2160-2174 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A methodology and analysis is presented to quantitatively characterize bacterial attachment and detachment kinetics on biomaterial surfaces in a laminar flow field as a function of shear stress. The spatial distribution of adherent bacteria on the surface of a radial-flow chamber is monitored via automated videomicroscopy with motorized three-axis stage and focus control, allowing rapid automated measurement of the attached cell density as a function of time and radial position. Intrinsic rate constants for attachment and detachment are defined and estimated by fitting mathematical models to the resulting data. The model for cell attachment accounts for the global transport of cell in the chamber to estimate the cells concentration near the collector surface. The model for cell detachment accounts for heterogeneity in the adhesion energy of the attached cell population. These models yield first-order attachment and detachment rate constants that intrinsically reflect the probabilities of bacteria attachment and detachment as a function of applied shear stress, depending on only the local interactions between the cell and the surface. The validity of each model was tested by statistical analyses of the goodness-of-fit to data that resulted from a study comparing adhesion of Staphylococcus aureus to three different polymeric surfaces of Varying surface properties and adhesive protein coatings.
    Additional Material: 12 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690410915
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    High-performance UV-curable urethane acrylates via deblocking chemistry (1996)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 62 (1996), S. 1361-1376 
    Details
    ISSN: 0021-8995
    Keywords: 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 , Physics
    Notes: Research in urethane-acrylate UV-curables has shown that these materials have mechanical properties inferior to those of thermoplastic polyurethanes with very similar composition owing to the high cross-link density in UV-curables; in particular, their ultimate extension is low (less than 100%). Past attempts at increasing the ultimate extension involved compromising the advantages of the UV-curing process. In this work, thermally labile bonds were made and then broken after curing, so as to incorporate thermoplastic polyurethane in the UV-cured polymer. This method achieved the desired improvement in ultimate properties without compromising the advantages of the UV-curing process. Two different reactive diluents and three different chain extenders were utilized, keeping the soft segment type (PPO), hard segment type (IPDI), and their weight fractions constant. The resulting polymers were similar to interpenetrating networks of linear or cross-linked polyurethanes and linear or cross-linked polyacrylates with properties entirely different from their UV-cured precursors, as well as the corresponding polyurethanes. All the materials involved were characterized by tensile testing and dynamic mechanical analysis. The ultimate extensions as well as the ultimate strength of the final polymers were found to be significantly greater than those of the corresponding UV-curable precursors, while the degree of phase separation was found to have changed. The differences in mechanical properties of the UV curables and the polyurethanes cannot be explained in terms of differences in cross-link density or composition and are probably due to differences in their morphology. © 1996 John Wiley & Sons, Inc.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
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    Paper (German National Licenses)
  • 3
    Electronic Resource
    Electronic Resource
    Studies on the tumor-promoting activity of polyurethanes: Depletion of inhibitory action of metabolic cooperation on the surface of a polyalkyleneurethane but not a polyetherurethane (1995)
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 29 (1995), S. 835-841 
    Details
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Methanol extracts prepared from three polyetherurethanes (PEUs), namely PU4, PU6, and PU8, which were synthesized using 4,4′-diphenylmethanediisocyanate, poly(tetramethylene oxide), and 1,4-butanediol, showed an inhibitory action on the gap-junctional intercellular communication in a V79 metabolic cooperation (MC) test system. However, the inhibitory potentials of methanol extracts did not correlate with the tumorigenic potential of the polyurethanes in 1-year rat implantation studies. When the MC test was carried out using glass dishes partly coated with low molecular weight PEU, the inhibitory activity was clearly detected on the surface of the polyurethane coating but not on that of the noncoated glass area. The inhibitory activity of the three PEUs investigated using polyurethanecoated dishes correlated with the values of the polyurethane's tumorigenic potential in the rat implantation study. Various polyurethanes containing polybutadiene (PBD), hydrogenated polybutadiene (HPBD), or a fluoropolyether glycol (FPEG) as the soft segment were also tested using coated dishes in the MC assay. The threshold inhibitory response of FPEG-PU was 10-fold less than that of PU4, and neither PBD-PU nor HPBD-PU showed any inhibition in the MC test system. Both the FPEG and aliphatic soft segment containing polyurethanes decreased, and had minimal influence on the gap junctional intercellular communication. Thus, the tumor-promoting potential of PBD-PU, HPBD-PU, and FPEG-PU was considered to be lower than those of the PEUs based on these in vitro test results. © 1995 John Wiley & Sons, Inc.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jbm.820290708
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    Paper (German National Licenses)
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  • 4
    Electronic Resource
    Electronic Resource
    Quantitative comparison of shear-dependent Staphylococcus aureus adhesion to three polyurethane ionomer analogs with distinct surface properties (1997)
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 36 (1997), S. 152-162 
    Details
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Bacterial adhesion is a central step in infection on biomaterial surfaces; however, the relation between biomaterial surface properties and adhesion remains poorly understood. To quantitatively determine the relationship among polyurethane surface properties, protein coating, and adhesion, we have compared attachment and detachment kinetics of Staphylococcus aureus on three different novel polyurethanes with different protein coatings. Rate constants for attachment or detachment were measured as a function of shear rate in a well-defined laminar flow field. The tested polyurethanes included a relatively hydrophobic-base polyetherurethane and hydrophilic anionomer and cationomer analogs of the base material. Materials were tested bare, or coated with human fibrinogen, plasma, or albumin. The results suggest that the presence of fibrinogen or plasma greatly enhance the attachment rate constants and decrease the detachment rate constants on all materials. The most extreme differences among the different materials were observed on the bare materials, with the base polyurethane being most resistant to both attachment and detachment. However, except for a reduced attachment rate constant on the plasma-coated sulfonated polyurethane, few differences in the rate constants were observed among protein-coated materials, suggesting the primary role of surface properties is masked by the presence of the adsorbed protein layer. © 1997 John Wiley & Sons, Inc.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
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    Paper (German National Licenses)
  • 5
    Electronic Resource
    Electronic Resource
    Influence of thrombus components in mediating staphylococcus aureus adhesion to polyurethane surfaces (1998)
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 40 (1998), S. 660-670 
    Details
    ISSN: 0021-9304
    Keywords: bacterial adhesion ; thrombosis ; polyurethane ; video microscopy ; adsorbed protein ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: The role of protein and cellular components of thrombi in mediating bacterial adhesion on artificial surfaces was investigated in this study. The attachment of Staphylococcus aureus on polyurethane surfaces was observed directly using an automated video microscopy system. Surfaces were preconditioned with components of platelet-fibrin thrombi, including fibrinogen, thrombin, plasma, and isolated platelets. Experiments were performed in a radial flow chamber, and attachment rate constants were compared on the preconditioned surfaces in an effort to understand the complex relationship that exists between bacterial infection and thrombosis on synthetic biomaterials. Preadsorption of fibrinogen to surfaces significantly increased S. aureus adhesion compared to those preadsorbed with albumin alone while the presence of fibrin dramatically increased bacterial attachment compared to plasma preadsorbed surfaces. While the presence of adherent platelets also increased bacterial attachment, fibrin appeared to play a larger role in mediating bacterial adhesion on polyurethane surfaces. Striking results were obtained on the zwitterionic phosphonated polyurethane for a number of pretreatment conditions with regard to decreased bacterial adhesion and fibrinogen deposition. © 1998 John Wiley & Sons, Inc. J Biomed Mater Res, 40, 660-670, 1998.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
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    Paper (German National Licenses)
  • 6
    Electronic Resource
    Electronic Resource
    Surface and blood-contacting properties of alkylsiloxane monolayers supported on silicone rubber (1995)
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 29 (1995), S. 535-548 
    Details
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Self-assembled monolayers of alkylsiloxanes supported on polydimethyl siloxane (PDMS) rubber were used as model systems to study the relation between blood compatibility and surface chemistry. The inner lumen of PDMS tubes was first treated with an oxygen plasma. The resultant oxidized surfaces were postderivatized by reacting them with alkyltrichlorosilanes to form the monolayer films. The chemical properties of the monolayers were controlled by varying the head-group chemical compositions. Surface derivatization was verified using variable-angle X-ray photoelectron spectroscopy (XPS or ESCA). Blood compatibility was evaluated using a canine ex vivo arteriovenous series shunt model. Surfaces grafted with hydrophobic head-groups as -CH3 and -CF3 had significantly lower platelet and fibrinogen deposition than the surfaces composed of hydrophilic groups such as -CO2CH3, -(CH2CH2O)3COCH3, and -(OCH2CH2)3OH. © 1995 John Wiley & Sons, Inc.
    Additional Material: 12 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jbm.820290414
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    Paper (German National Licenses)
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