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  • 1
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Biopolymers 47 (1998), S. 185-193 
    ISSN: 0006-3525
    Keywords: surface modification ; template approach ; self-assembly ; protein monolayer ; molecular imprinting ; implant material ; protein adsorption - X-ray photoelectron spectroscopy ; surface pattern - biocompatibility of, cyclic peptide for, porphyrin for ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Protein layers are deposited on the surface of implanted biomaterials. Better understanding of the interaction between the surface protein layers and the biological system would lead to the development of future biomaterials with superior biocompatibilities. Well-organized biorecognizable surfaces can be formed with various template molecules that provide an appropriate spacing for the attachment of recognition groups to the modified surface. Silane coupling reagents, porphyrin thiols, and cyclic peptides are being used as templates to introduce nano-scale patterns on solid surfaces. Synthesis of these templates and characterization of the modified surface are described. © 1998 John Wiley & Sons, Inc. Biopoly 47: 185-193, 1998
    Additional Material: 7 Ill.
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  • 2
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 22 (1988), S. 383-404 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Adhesion of cells to substrates strongly influences many of their functions and therefore plays an important role in a variety of processes, including phagocytosis, hemostasis, and the response of tissue to implanted materials. In previous studies, the influence of substrate hydrophilicity on cell adhesion has not been separated from effects due to major differences in other properties of the substrate, such as charge, rigidity, and the specific chemical composition of the materials. In addition, very few careful studies of the force required for cell detachment from various substrates have been performed. In this study, 3T3 cell detachment from a chemically homologous series of copolymers based on hydroxyethylmethacrylate (HEMA) and ethylmethacrylate (EMA) was measured with a spinning-disc apparatus. The spinning-disc technique allowed measurements of cell detachment over a wide range of applied shear stress on each sample. Cell detachment did not occur until a critical value of shear stress was exceeded. The critical shear stress of detachment decreased linearly with increasing HEMA content, from 18 dynes/cm2 on poly-EMA to 0 on the polymers containing 83% or more HEMA. “Plating efficiency,” calculated as the fraction of cells initially applied which remained after dip rinsing the surfaces, did not vary significantly among most of the copolymers. Dip rinsing, however, exposes the cells to only one, relatively low shear stress (estimated to be somewhat less than 3 dynes/cm2). The existence of a critical shear stress for 3T3 cell detachment suggests that cell adhesion to surfaces cannot be fully understood with single shear stress methods because cells may attach with a wide range of strengths which are either all above or all below the applied shear stress. The influence of surface hydrophilicity on cell adhesion and the variety of forces which may contribute to this phenomenon are discussed.
    Additional Material: 7 Ill.
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  • 3
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 26 (1992), S. 273-289 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: We have studied the surface chemistry of two lots of Biomer™ (BSP067 and BSUAOOl), and widely used commercial poly(ether urethane) (PEU). Although transmission infrared adsorption studies revealed no differences in the bulk chemistry of the two lots, the surface chemistry, as seen by x-ray photoelectron spectroscopy (XPS) and static secondary ion mass spectrometry (SIMS), was different. Lot BSP067 showed softsegment enrichment at the surface, which is typical of PEU. Lot BSUAOOl showed no evidence of either hard- or soft-segment PEU components at the surface. The surface of this lot was completely covered with a nonextractable additive identified as poly(diisopropy1 amino ethyl methacrylate). Small amounts of a low-molecular-weight antioxidant were observed at the surface of both samples. Because the biological response to polymers is dependent on surface structure, these results are of considerable importance to biomaterials research.
    Additional Material: 7 Ill.
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  • 4
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 20 (1986), S. 799-815 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: The cellular response to films of cast Biomer and acetone-extracted Biomer were investigated over a 21-day implantation period, using an in vivo cage implant system. Film samples were characterized by scanning electron microscopy (SEM), attenuated total reflectance infrared (ATRIR), electron spectroscopy for chemical analysis (ESCA) and by contact angle measurements before implantation, and by SEM and ESCA after implantation and cleaning. Cellular and protein components of the inflammatory response were analyzed at periodic observation points after implantation. In addition, film samples were retrieved at 4, 7, and 21 days after implantation and analyzed for leukocyte adhesion by light microscopy and SEM. The results demonstrated that cast Biomer contains an extractable fraction, which when removed significantly improves the biocompatibility of the material.
    Additional Material: 4 Ill.
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  • 5
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 22 (1988), S. 509-527 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: In vitro biodegradation studies were performed to assess the long-term stability of poly(ether urethane) (PEU) implants. Three PEU's and one poly(ester urethane) were treated with enzymes characteristic of those released from inflammatory cells during the foreign body reaction. In addition, the effect of hydrogen peroxide was observed to examine oxidative degradation. Polymers were prepared as thin films on glass, gold, silver, and copper substrates to test the possibility of metal-catalyzed degradation. Molecular weights and polydispersities of the polymers were measured by gel permeation chromatography (GPC) before and after treatment. Changes in peak shape and location were also monitored. The results demonstrate that varying degrees of both enzymatic and oxidative degradation occurred.
    Additional Material: 4 Ill.
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  • 6
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 20 (1986), S. 739-772 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Fibrinogen adsorption on polymers from blood may mediate or potentiate thrombosis because of its involvement in both the intrinsic clotting system and the formation of platelet aggregates. While the kinetics of fibrinogen adsorption from plasma in vitro have previously been found to be very different on polar and nonpolar surfaces [T. A Horbett, “The kinetics of adsorption of plasma proteins to a series of hydrophilic-hydrophobic copolymers,” ACS Org. Coat. Plas. Chem., 40, 642-646 (1979)] the significance of this difference with respect to thrombogenesis in vivo has not been clarified. In this study, the kinetics of deposition of baboon 125I fibrinogen from plasma in vitro or from blood in vivo on a series of polymers was measured. The polymers chosen for this study had previously been found to have a large range in surface polarity and reactivity in the in vivo baboon shunt model. The kinetics of fibrinogen adsorption in vitro were observed to be of three types, depending on the polymer: (1) high initial adsorption decreasing to a lower steady state value; (2) constant throughout the time course; (3) low initial adsorption rising steadily to a plateau value. In vivo, fibrinogen deposition kinetics were of two types: (1) low, constant deposition throughout the time course, independent of heparinization; (2) low deposition initially followed by a second phase of greatly increased deposition (probably as fibrin) which was prevented or greatly decreased by heparinizing the animals. Polymers for which fibrinogen adsorption increased to a plateau in vitro were found to have a heparin inhibitable second phase of enhanced in vivo fibrinogen deposition. These polymers also have been found in previous studies to enhance the rate of platelet destruction when used as in vivo shunts on baboons. Conversely, most polymers with high initial in vitro fibrinogen adsorption followed by a decrease had low fibrinogen deposition behavior in vivo and were also minimally destructive of platelets. The adsorption kinetics of fibrinogen to polymers from blood in vivo and in vitro and the consumption of platelets in vivo induced by the polymers all vary with polymer polarity. More polar polymers had in vitro fibrinogen kinetics characterized by a rise to a plateau, in vivo fibrinogen deposition characterized by a second stage of great increase inhibitable by heparin, and enhanced platelet consumption. The correlation of three separate indicators of surface thrombogenicity with surface polarity suggests that more polar materials may be more thrombogenic because of an influence on the way in which fibrinogen interacts with these surfaces.
    Additional Material: 10 Ill.
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  • 7
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 24 (1990), S. 547-571 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Previously observed bioactivity of poly(dimethylsiloxane)-poly(ethyelene oxide)-heparin (PDMS-PEO-Hep) triblock copolymers has prompted studies of the surface and bulk character of this copolymer using angular-dependent electron spectroscopy for chemical analysis (ADESCA), static secondary mass spectroscopy (SIMS), differential scanning calorimetry (DSC), and thermogravimetric analysis (TGA). Because the low-energy PDMS phase dominates surfaces of this copolymer when solvent cast under air or vacuum conditions, attempts were made to explain surface restructuring and rearrangements induced in hydrated or aqueous environments that permit surface accessibility and bioactivity of heparin moieties. Based on comparisons with PDMS, PEO, and heparin homopolymers, PEO/heparin blends, and an unheparinized PDMS-PEO diblock copolymer, PDMS-PEO-heparin demonstrates both phase-mixed and phase-separated regions in DSC analysis. During annealing cycles above the Tg values of the copolymer constituents, phase-mixed regions become increasingly phase separated and PEO enriched. TGA analysis confirmed the presence of block copolymer constituents and presented evidence of intermolecular segmental interactions, hence phase-mixing in the copolymers. ADESCA analysis indicates that the outer 5 Å of both the PDMS-PEO and PDMS-PEO-Hep copolymers is essentially pure PDMS. However, significant amounts of PEO are detected 5 to 20 Å below the surface. Static SIMS also detects the presence of PDMS at the surfaces of the PDMS-PEO and PDMS-PEO-Hep copolymers. Compositional models based on ADESCA, SIMS, and DSC data are presented for desiccated and hydrated copolymer surfaces.
    Additional Material: 16 Ill.
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  • 8
    Electronic Resource
    Electronic Resource
    Chichester [u.a.] : Wiley-Blackwell
    Surface and Interface Analysis 6 (1984), S. 184-192 
    ISSN: 0142-2421
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: Static SIMS spectra from essentially undamaged acrylic polymers have been obtained for total ions doses of 2 × 1012 ions cm-2. For a series of polymethacrylates the spectra can be interpreted in terms of a constant contribution from the polymer backbone plus dominant fragments from the ester side chain. Isomeric butyl methacrylate polymers can be distinguished. Negative ion spectra reflect the O:C atomic ratio of the bulk polymer. Positive ion relative intensities from ethyl methacrylate: hydroxyethyl methacrylate random copolymers correlate with polymer composition. Previous SIMS data from polymethacrylates have been shown to represent highly damaged surfaces.
    Additional Material: 11 Ill.
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  • 9
    Electronic Resource
    Electronic Resource
    Chichester [u.a.] : Wiley-Blackwell
    Surface and Interface Analysis 14 (1989), S. 443-450 
    ISSN: 0142-2421
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: An algorithm for generating depth profiles from angle-dependent XPS data has been developed. The algorithm uses the regularization method with non-negativity constraints. Four criteria for determining the optimal amount of solution smoothing have been investigated. A criterion that uses the least-squared error in the regenerated data set proved most effective for selecting the optimal smoothing. Simulated data for a two-layer sample were used to investigate the effects of the number of data points, where each data point consisted of the spectra acquired at a take-off angle. Simulated data were also used to investigate the effect of random error on the calculated depth profiles. Increasing the number of data points improved the resolution at the interface. Greater than 10% error could be added to the data without affecting the stability of the algorithm. The algorithm has also been tested on actual angle-dependent XPS data sets from a thin polyurethane film on gold, a thin silicon oxide film on silicon, and a thick polyetherurethane film on glass. Performance of the regularization algorithm has been compared to an algorithm that uses a singular value decomposition of angle-dependent XPS data to generate depth profiles. The regularization algorithm demonstrates significantly improved stability and accuracy with roughly equal computational difficulty. Using the regularization algorithm, a quantitative estimate of the depth profile in the upper 100 Å region of a sample can be calculated using data with 〉 10% error and using as few as three data points.
    Additional Material: 6 Ill.
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  • 10
    Electronic Resource
    Electronic Resource
    Chichester [u.a.] : Wiley-Blackwell
    Surface and Interface Analysis 18 (1992), S. 210-216 
    ISSN: 0142-2421
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: Results are presented for a tandem-SIMS investigation of the fragmentation patterns of secondary ions sputtered from the surface of poly(vinyl methyl ether) (PVME). A complete fragmentation sequence is deduced which is capable of explaining the formation of most of the major ions observed in the SIMS spectrum in terms of fragmentation steps proceeding from the largest secondary ion observed. The fragmentation steps involved in the formation of these ions are discussed and the secondary ion structures are identified.
    Additional Material: 5 Ill.
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