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  • 1
    Electronic Resource
    Electronic Resource
    Ex vivo complement protein adsorption on positively and negatively charged cellulose dialyser membranes (1997)
    Springer
    Journal of materials science 8 (1997), S. 287-296 
    Details
    ISSN: 1573-4838
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Technology
    Notes: Abstract An ex vivo test system was used to measure complement protein C3 and factor B adsorption onto small dialyser modules made from regenerated and modified cellulosic hollow fibre membranes in which positive diethylaminoethyl (DEAE) or negative carboxymethyl (CM) groups were introduced into the cellulose matrix. The extracorporeal system, which included test-dialysers and the dialysis environment, allowed the use of labelled proteins without contaminating the blood donors which were connected in an open-loop fashion to the extracorporeal test system. The modules were removed at selected time points from the extracorporeal system for radioactivity counting. The results were used to evaluate the mechanisms involved in complement reactions to foreign surfaces. The system therefore allowed the analysis of complement protein adsorption occurring in the dialyser modules and its relationship to the complement generation rate in the extracorporeal system to be evaluated. It was possible to demonstrate that significant complement C3 and factor B adsorption occurred in the test modules made of cellulosic membranes. Complement adsorption as a function of the pH and the release reaction of the adsorbed C3 and factor B after membrane blood perfusion were therefore found to be variable according to the cellulosic membrane type and the presence of positive or negative charged groups within the cellulose matrix. The data obtained from the ex vivo model therefore provided additional evidence on the discussion of the mechanisms involved in the increased complement activation by regenerated cellulose and in its attenuation by DEAE- or CM-modified cellulose.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1018560211844
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  • 2
    Electronic Resource
    Electronic Resource
    Complement activation by cellulose: investigation of the effects of time, area, flow rate, shear rate and temperature on C3a generation in vitro, using a parallel plate flow cell (1998)
    Springer
    Journal of materials science 9 (1998), S. 409-414 
    Details
    ISSN: 1573-4838
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Technology
    Notes: Abstract The development and utilization of a parallel plate flow system to study the blood response to flat sheet biomaterials, is described. Unlike most other parallel plate flow systems, which have been used to study cellular interactions with biomaterials, the controlled flow test cell described below employs the test materials on both sides of the channel through which the blood flows. The flow cell is used to conduct an investigation into the in vitro generation of C3a by a regenerated cellulose membrane, Cuprophan. The effects of experimental variables such as temperature, blood flow rate, contact area and wall shear rate on C3a generation by Cuprophan were studied. The results show that C3a generation by Cuprophan is lower at 12 °C than at 22 °C, which is in turn lower than C3a generation at 37 °C. Furthermore, a decrease in contact area, and increase in wall shear rate and blood flow rate, can produce a decrease in C3a concentration.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1013287614418
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  • 3
    Electronic Resource
    Electronic Resource
    Blood interactions with plasticized poly(vinyl chloride): relevance of plasticizer selection (1999)
    Springer
    Journal of materials science 10 (1999), S. 527-531 
    Details
    ISSN: 1573-4838
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Technology
    Notes: Abstract An investigation has been made of blood interactions with plasticized poly(vinyl chloride) (PVC) biomaterials in tubular form, taking into account the influence on the blood response of the polymer, antithrombotic agent, blood condition and test procedure. In vitro and ex vivo procedures were used to achieve a comparison between PVC plasticized with di- (2-ethylhexyl)phthalate (DEHP) and with tri-(2-ethylhexyl)trimellitate (TEHTM). The blood response was monitored in terms of the measurement of fibrinogen adsorption capacity, thrombin–antithrombin III complex (TAT) and the complement component C3a. Surface characterization of the polymers was performed by X-ray photoelectron spectroscopy (XPS). The data obtained indicate that in comparison with DEHP-PVC, there is a higher reactivity for TEHTM-PVC, which correlates with the plasticizer distribution at the polymer surface. © 1999 Kluwer Academic Publishers
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1008912213420
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  • 4
    Electronic Resource
    Electronic Resource
    Quantitative evaluation of the growth of established cell lines on the surface of collagen, collagen composite and reconstituted basement membrane (1992)
    Springer
    Urological research 20 (1992), S. 285-288 
    Details
    ISSN: 1434-0879
    Keywords: Collagen ; Cell culture ; Urothelium
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary As a step in the development of a system for assessing growth of human urothelium and transitional cell carcinoma, the growth of two established cell lines on collagen-based membranes has been evaluated. HT1080 (metastatic human fibrosarcoma) and WI38 VA13 (virus-transformed human fibroblasts) were grown on substrates of collagen, collagen/hyaluronic acid or chondroitin sulphate and reconstituted basement membrane (Matrigel). Cell growth was quantified using a new fluorimetric assay utilizing carboxyfluorescein diacetate. There were differences in morphology between cells grown on collagen and those grown on polystyrene. There were, however, no differences in growth of the WI38 VA13 cells on collagen compared with polystyrene, but growth of the HT1080 cells was increased on membranes of collagen/2:5% hyaluronic acid and collagen/5% chondroitin sulphate, and decreased on Matrigel. Adequate growth on collagen substrates is dependent on cell line. The fluorimetric assay used was suitable for quantifying cell growth on such substrates.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00300260
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  • 5
    Electronic Resource
    Electronic Resource
    Chemical modification of acrylonitrile copolymers: Reaction of cationic copolymers with ethylene oxide (1975)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 19 (1975), S. 1503-1506 
    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: Copolymers of tertiary amines have been reacted with ethylene oxides gas. The reaction induces low temperature cyclization and increases polymer hydrophilicity. When the co-polymer is in film form, water permeability is dependent on ethylene oxide processing time and temperature.The behavior of the copolymer films when treated with ethylene oxide is contrasted with the effects due to thermal treatment of acrylonitrile copolymers.
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1975.070190602
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  • 6
    Electronic Resource
    Electronic Resource
    Acrylonitrile copolymer films: Influence of modification by reaction with ethylene oxide on biological degradation (1979)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 23 (1979), S. 1449-1452 
    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: The biological degradation of acrylonitrile-dimethylaminoethyl methacrylate and acrylonitrile-acrylic acid copolymers has been studied by evaluating copolymer films in a continuous in vitro rumen system. The copolymer films were examined before and after modification by reaction with ethylene oxide gas. The degradation of the acrylonitrile-dimethylaminoethyl methacrylate copolymer followed a pattern similar to that occurring on thermal degradation. Modification by reaction with ethylene oxide gas, which induces C=N conjugation, did not improve the resistance to degradation. The acrylonitrile-acrylic acid copolymer films disintegrated, but on prior modification by reaction with ethylene oxide they remained virtually unaltered. Modification of the acrylonitrile-acrylic acid copolymer results in crosslinking with an absence of C=N conjugation, leading to improved resistance to biological degradation.
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1979.070230515
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  • 7
    Electronic Resource
    Electronic Resource
    Silicone rubber and natural rubber as biomaterials (1980)
    Springer
    Medical & biological engineering & computing 18 (1980), S. 538-540 
    Details
    ISSN: 1741-0444
    Keywords: Biocompatibility ; Biomaterial ; Elastomer ; Natural rubber ; Silicone rubber
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract The roles of silicone rubber and natural rubber as biomaterials are contrasted, with silicone rubber being widely used and natural rubber having, as yet, found limited application. Relevant properties of both elastomers are described, applications are discussed and possible future developments are considered.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02443332
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  • 8
    Electronic Resource
    Electronic Resource
    Perm-selective dialysis membranes. II. Films based on acrylic acid-n-butyl methacrylate copolymers - a critical comparison with cellulose films (1973)
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 7 (1973), S. 3-37 
    Details
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: New synthetic anionic membranes have been developed as replacements for the cellulose membranes currently used to remove blood toxins and water in hemodialyzers. The membranes are solvent-cast on to polyethylene sheets from copolymers of acrylic acid with various alkyl methacrylates. Membranes from copolymers of acrylic acid and n-butyl methacrylate show most promise as alternative hemodialysis membranes. The copolymers are prepared using modified emulsion copolymerization techniques with sequential monomeric additions in order to yield homogeneous polymers with the high molecular weight necessary for good film-forming characteristics. Permeability of the synthetic membranes to blood components, rates of water removal by ultrafiltration, and mechanical properties of membranes are measured and compared with standard 150 and 300PT cellulose films. Results for cellulose films confirm previous conclusions that permeability is principally proportional to the inverse molecular volume of the diffusing solute, while new anionic synthetic membranes show selectivity to basic blood solutes and operate by an “assisted diffusion” mechanism. A method is reported of improving mechanical properties while maintaining high permeability rates for blood solutes and high water ultrafiltration rates, by treating membranes with ethylene oxide gas, a clinical sterilizing agent.
    Additional Material: 15 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jbm.820070103
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  • 9
    Electronic Resource
    Electronic Resource
    Determination of contact phase activation by the measurement of the activity of supernatant and membrane surface-adsorbed factor XII (FXII): Its relevance as a useful parameter for the in vitro assessment of haemodialysis membranes (1996)
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 31 (1996), S. 63-70 
    Details
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: We investigated hemodialysis membrane biocompatibility with respect to contact phase activation by determination of FXII-like activity (FXIIA) on the membrane surface and in the supernatant phase, during plasma contact with various hemodialysis membranes using an in vitro incubation test cell. The results were compared to the influence of these membranes on the activation of purified FXII. A time course for the generation of activated FXII using purified FXII solution at physiologic concentrations on two similar negatively charged polymers was performed. The membranes assessed were regenerated cellulose (Cuprophan; Akzo Faser AG, Germany), modified cellulosic (Hemophan; Akzo Faser AG), acrylonitrile-sodium methallyl copolymer-based membrane AN69S (Hospal, France), and SPAN, a new polyacrylonitrile-based copolymer (Akzo Nobel AG). The plasma FXIIA at the membranes surface was significantly different between the membranes, while the supernatant phase FXIIA exhibited no significant differences. In contrast, activation of purified FXII in a plasma-free system with respect to supernatant activity indicated significant differences between the materials. A similar finding for the membrane-bound factor XIIA was also observed when purified factor XII was used. The membrane-bound FXIIA values observed in the plasma system containing heparin were significantly greater than in citrated plasma. This demonstrated the strong influence of heparin and the interaction of other plasma components to the membrane surface on the activation of contact phase of coagulation. © 1996 John Wiley & Sons, Inc.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Perm-selective dialysis membranes. I. Films based on dimethylaminoethyl methacrylate copolymers (1971)
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 5 (1971), S. 415-445 
    Details
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: New synthetic polymer membranes prepared from copolymers of dimethylaminoethyl methacrylate are reported. Membrane transport characteristics are compared with those of standard cellulose films currently used in hemodialysis. The membranes are obtained as films by casting solutions of vinyl copolymers prepared by emulsion polymerization techniques. The new membranes show selectivity towards certain blood components under the test conditions used. The clinical procedure for ethylene oxide sterilization has been adapted to give chemical modification of dimethylaminoethyl methacrylate tertiary amine groups. With acrylonitrile as comonomer, polymer membranes which are both watersensitive and insoluble are obtained. The permeability of such films is controlled by varying processing time. Infrared spectra of processed and unprocessed films are discussed and reasons put forward for the change in membrane properties brought about by processing. Membrane behavior when acrylonitrile is replaced by methacrylonitrile or methyl methacrylate indicates the probable necessity of having a strongly electron-attracting comonomer for successful modification.
    Additional Material: 16 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jbm.820050502
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