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1

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Sterilization of heparinized Cuprophan hemodialysis membranes (1996)

Hoopen, H. W. M. ; Hinrichs, W. L. J. ; Engbers, G. H. M. ; [et al.]

Springer

Journal of materials science 7 (1996), S. 699-704

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ISSN: 1573-4838

Source: Springer Online Journal Archives 1860-2000

Topics: Medicine , Technology

Notes: The effects of sterilization of dry heparinized Cuprophan hemodialysis membranes by means of ethylene oxide (EtO) exposure, gamma irradiation, or steam on the anticoagulant activity and chemical characteristics of immobilized heparin and the permeability of the membrane were investigated. Sterilization did not result in a release of heparin or heparin fragments from heparinized Cuprophan. Sterilization of heparinized Cuprophan by means of EtO exposure and gamma irradiation induced a slight, insignificant decrease of the anticoagulant activity. In contrast, steam-sterilized heparinized Cuprophan showed a higher anticoagulant activity than unsterilized heparinized Cuprophan, which was most likely caused by cleavage of some of the covalent bonds between heparin and Cupropha. The effects of sterilization on the permeability of unmodified Cuprophan and heparinized Cuprophan were compared. The permeability of unmodified Cuprophan for vitamin B12 (Vit B12) and sulfobromophthalein (SBP) was reduced by 20–35% after EtO exposure and gamma irradiation and was reduced by 90–95% after steam sterilization. The water permeability of unmodified Cuprophan remained the same after EtO exposure and gamma irradiation but also dramatically reduced after steam sterilization. These reductions were ascribed to the collapse of pores of the membrane. The permeability of heparinized Cuprophan was not affected by EtO exposure and gamma irradiation but dramatically reduced after steam sterilization, although to a lesser extent than in the case of unmodified Cuprophan. Apparently, the presence of immobilized heparin (partially) prevented the collapse of pores during sterilization. Gamma irradiation was recommended as the preferred method of sterilization for heparinized Cuprophan.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF00123410

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Mechanism of the Immobilization of Surfactants on Polymer Surfaces by Means of an Argon Plasma Treatment: Influence of UV Radiation (1999)

Lens, J. P. ; Spaay, B. ; Terlingen, J. G. A. ; [et al.]

Springer

Plasmas and polymers 4 (1999), S. 159-182

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ISSN: 1572-8978

Keywords: Surface modification ; argon plasma treatment ; vacuum UV ; carboxylic acid groups ; Langmuir probe measurements

Source: Springer Online Journal Archives 1860-2000

Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Technology

Notes: Abstract The mechanism of the immobilization of the surfactant sodium 10-undecenoate (C11(:)) on poly(ethylene) (PE) by means of an argon plasma treatment has been investigated. In particular, the influence of the vacuum ultraviolet (UV) radiation emitted by the argon plasma on the immobilization was studied. For this purpose, PE samples were coated with C11(:) (PE/C11(:) samples) and treated with an argon plasma under different conditions. PE/C11(:) samples were placed inside (glow) and outside (afterglow) the visible region of the plasma. Additionally, polymer samples that were placed in the glow of the plasma were covered with lithium fluoride or quartz crystals. These materials are transparent for electromagnetic radiation with a wavelength longer than 104 and 150 nm, respectively. Derivatization X-ray Photoelectron Spectroscopy was applied to characterize the modified polymer surfaces. It was demonstrated that vacuum UV radiation with a wavelength shorter than 150 nm made a predominant contribution to the process of immobilization. Under certain conditions it was possible to retain about 30% of the functional groups of the initially coated surfactant layer on PE. Furthermore, the UV radiation accounted for etching of PE and PE/C11(:) surfaces and initiated oxidation of the polymer surfaces.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1023/A:1021801009780

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Mechanism of the immobilization of surfactants on polymeric surfaces by means of an argon plasma treatment: Influence of the chemical structure of surfactant and substrate (1998)

Lens, J. P. ; Terlingen, J. G. A. ; Engbers, G. H. M. ; [et al.]

Bognor Regis [u.a.] : Wiley-Blackwell

Journal of Polymer Science Part A: Polymer Chemistry 36 (1998), S. 1829-1846

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ISSN: 0887-624X

Keywords: surface modification ; argon plasma treatment ; poly(ethylene) ; poly(propylene) ; poly(cis-butadiene) ; carboxylic acid groups ; XPS ; SSIMS ; Chemistry ; Polymer and Materials Science

Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Chemistry and Pharmacology

Notes: In this article, a study on the mechanism of the immobilization of surfactants on polymeric surfaces by means of an argon plasma treatment is described. The unsaturated surfactant sodium 10-undecenoate [C11(:)] and the saturated surfactant sodium dodecanoate (C12) were immobilized on poly(ethylene) (PE), poly(propylene) (PP), and poly(cis-butadiene) (PB) surfaces. This was accomplished by treating polymeric substrates that were coated with C11(:) or C12 with an argon plasma. Derivatization X-ray Photoelectron Spectroscopy (XPS) and Static Secondary Ion Mass Spectrometry (SSIMS) showed that during the plasma treatment surfactants were covalently coupled to the polymeric surfaces. The chemical structure of both the surfactant and the polymeric substrate influenced the immobilization efficiency. At an optimal treatment time of 5 s, about 28 and 6% of the initial amount of carboxylate groups in the precoated C11(:) and C12 layer, respectively, was retained at the PE surface. The immobilization efficiencies of C11(:) and C12 on PP were about 20 and 9%, respectively. The immobilization efficiency of C11(:) and C12 on PB were both about 7%. The results obtained in this study indicate that the immobilization proceeds via a radical mechanism. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 1829-1846, 1998

Additional Material: 8 Ill.

Type of Medium: Electronic Resource

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Interaction of antithrombin III with surface-immobilized albumin - heparin conjugates (1995)

van Delden, C. J. ; Engbers, G. H. M. ; Feijen, Jan

Hoboken, NJ : Wiley-Blackwell

Journal of Biomedical Materials Research 29 (1995), S. 1317-1329

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ISSN: 0021-9304

Keywords: Chemistry ; Polymer and Materials Science

Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Medicine , Technology

Notes: The interaction between antithrombin III (ATIII) and albumin-heparin conjugates covalently coupled onto carboxylated polystyrene beads either in buffer containing albumin or in plasma was studied using 14C-labeled ATIII. Binding isotherms of ATIII were modeled using a summation of two Langmuir equations. These equations describe the binding of ATIII to two different sets of binding sites, one with a high, the other with a low affinity for ATIII. The average binding constants for the binding of ATIII to these sites are 9 × 106 L/mol and 0.3 × 106 L/mol, respectively. The binding of ATIII to surface binding sites with a high affinity for ATIII was correlated with the presence of specific ATIII binding sites in the immobilized heparin. Binding of ATIII from albumin solutions to binding sites with a low affinity for ATIII was dominated by nonspecific binding of ATIII to the immobilized heparin. A third small fraction of the surface bound ATIII is probably adsorbed to sites on the surface not covered with heparin. In the case of the binding of ATIII to the heparinized surface from plasma solutions, a fraction of initially adsorbed ATIII was desorbed by other plasma proteins. This desorption in combination with direct competition between ATIII and other plasma proteins resulted in lower ATIII surface concentrations using plasma as compared to the ATIII surface concentrations obtained using albumin solutions. The binding of ATIII to nonspecific binding sites was almost completely inhibited in the presence of plasma proteins. The amount of ATIII bound to immobilized heparin via specific ATIII binding sites was 30% lower in plasma solutions as compared to the specific binding of ATIII using albumin solutions. It is concluded that the accessibility of immobilized heparin for ATIII in plasma decreases by binding of heparin-binding proteins onto the immobilized heparin and/or by adsorption of other plasma proteins on the heparinized surface. © 1995 John Wiley & Sons, Inc.

Additional Material: 12 Ill.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1002/jbm.820291103

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5

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An in vitro study of the adhesion of blood platelets onto vascular catheters. Part I (1987)

Engbers, G. H. M. ; Dost, L. ; Hennink, W. E. ; [et al.]

Hoboken, NJ : Wiley-Blackwell

Journal of Biomedical Materials Research 21 (1987), S. 613-627

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ISSN: 0021-9304

Keywords: Chemistry ; Polymer and Materials Science

Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Medicine , Technology

Notes: The adhesion of human blood platelets onto vascular catheters was studied using a specially designed perfusion chamber. Polyurethane catheters were exposed to citrated human blood for different periods (up to 20 min) and at different wall shear rates (190, 260, 330 sec-1). The rate of platelet adhesion was determined using 111In-labeled platelets, while the morphology of adhering platelets was investigated using scanning electron microscopy. A linear increase in platelet adhesion was found within the first 10 min of perfusion, after which a plateau value was reached. The number of adhering platelets did not vary significantly with the shear rates applied, which may indicate that within the range of shear rates studied, the adhesion of platelets onto the catheter surface is mainly determined by the rate of the reaction between the platelets and the material surface. Catheters coated with a conjugate of heparin and albumin showed a four- to five-fold reduction in platelet adhesion as compared to uncoated catheters. This reduction in platelet adhesion was not only due to the presence of albumin moieties at the surface but also to the presence of heparin residues in the adsorbed albumin-heparin conjugate.

Additional Material: 9 Ill.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1002/jbm.820210507

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6

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In vitro evaluation of heparinized Cuprophan hemodialysis membranes (1997)

Hinrichs, W. L. J. ; ten Hoopen, H. W. M. ; Engbers, G. H. M. ; [et al.]

Hoboken, NJ : Wiley-Blackwell

Journal of Biomedical Materials Research 35 (1997), S. 443-450

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ISSN: 0021-9304

Keywords: Chemistry ; Polymer and Materials Science

Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Medicine , Technology

Notes: Cuprophan hemodialysis membranes can be heparinized using N,N′-carbonyldiimidazole (CDI) as a coupling agent. In this study, the characteristics of heparinized Cuprophan membranes have been evaluated. After immobilization, heparin partially retained its biologic activity. An anticoagulant activity of 12.4 ± 4.2 mU/cm2 was measured using a thrombin inactivation assay. Immobilized heparin also displayed an anti-complement activity. After contact with human serum, heparinized Cuprophan induced no generation of significant amounts of fluid phase terminal complement complex (TCC), whereas untreated Cuprophan induced the generation of substantial amounts of TCC. Heparinization did not affect the permeability of Cuprophan for model solutes with molecular weights up to 12,000 g/mol except for sulfobromophthalein sodium salt. The permeability of Cuprophan for sulfobromophthalein sodium salt was slightly decreased after heparinization. The ultrafiltration rate of Cuprophan increased by about 30% after heparinization, probably owing to an increased swelling of the membrane in water. Heparinized Cuprophan incubated in phosphate-buffered saline at 37°C showed some release of heparin. These amounts of released heparin, however, were very low as compared to the amounts of heparin which are systemically administered during clinical hemodialysis treatment. It is concluded that Cuprophan membranes heparinized by means of the CDI-activation procedure are highly promising for application in hemodialyzers to be used for the treatment of patients with reduced or without systemic administration of heparin. © 1997 John Wiley & Sons, Inc.

Additional Material: 3 Ill.

Type of Medium: Electronic Resource

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