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  • 1
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 27 (1993), S. 89-95 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Thrombin adsorption to polyvinyl alcohol (PVA) was different from its adsorption to polyethylene (PE) - not so much in amount, but in its affinity. Thrombin was more easily displaced from polyethylene and its adsorption was more readily prevented by prior or simultaneous exposure to albumin. From PVA (or heparin-PVA), only ∼ 30% of the adsorbed protein could be removed by a series of eluents, including even harsh ones such as 2.5M NaOH and 6M guanidine;〉85% could be removed from PE. Thrombin adsorption to PVA was not affected by the presence of BSA in solution or at the surface, but was virtually prevented on PE by preexposure to or adsorption with BSA. Heparin-PVA was not much different than PVA in most of these experiments, but did exhibit a “Vroman effect”. In the absence of fibringen or antithrombin III, there was a maximum in thrombin adsorption from plasma at a plasma concentration of 1%. The behavior on this surface was dependent on both exposure time and protein concentration. These studies highlight the complexity of the interaction between plasma proteins and polymer surfaces (particularly hydrogel surfaces) and the difficulty of obtaining a clear picture of what happens when a single protein interacts with a polymer in the presence of other proteins. © 1993 John Wiley & Sons, Inc.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 22 (1988), S. 673-685 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: The diffusivities of thrombin and antithrombin III in a heparin-polyvinyl alcohol hydrogel were estimated and used to demonstrate that diffusion limits the effectiveness of the immobilized heparin in the interior of such hydrogels. Diffusivities were calculated from permeabilities and partition coefficients measured with films in a diffusion chamber apparatus. The diffusion coefficients were estimated to be 6 ± 4 × 10-8 cm2/s for thrombin and 4 ± 2 × 10-8 cm2/s for antithormbin III in 10% gel membranes with or without immobilized heparin. Using the diffusivity of thrombin and a Thiele-type modulus, the effectiveness factor of a spherical heparin-PVA bead used to accelerate the inactivation of thrombin by antithrombin III was found to be 4-9% (diameter range 250-105 μm). While indicating that diffusion of thrombin limited the full utilization of the immobilized heparin, these values for the effectiveness factor could not completely account for the low apparent heparin activity (0.2%) in a thrombin time test of heparin-PVA “beads” (J. Biomed. Mater. Res., 17, 359 (1983)). Other factors such as the immobilization chemistry or the diffusion of thrombin-antithrombin III complex must be considered for a full explanation of the thrombin time results.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 26 (1992), S. 947-958 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: More radiolabeled thrombin was adsorbed to heparin-polyvinyl alcohol (PVA) than to PVA, consistent with a specific interaction with the immobilized heparin. The maximum surface concentration on heparin-PVA was estimated to be ∼450 nmol/m2 with an apparent affinity constant (Ka,) of 2.5μM-1; on PVA, the plateau concentration was 10 nmol/m2 with a Ka 〈 1 nM-1. There was little difference in bovine serum albumin (BSA) adsorption between PVA and heparin PVA. Interestingly, thrombin adsorption to polyethylene was indistinguishable from that to PVA despite the large difference in surface chemistry. BSA adsorbed to polyethylene with higher affinity than to the hydrogels, although the plateau concentrations were comparable. The adsorbed thrombin was biologically inactive at least towards chromogenic substrate, with the residual activity on PVA unaffected by subsequent incubations with antithrombin 111. PVA and heparin-PVA presented a heterogeneous and complex substrate for interaction with proteins. The adsorbed protein was likely present in multiple states depending on the groups with which it interacted.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
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