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Heparin coating durability on artificial heart valves studied by XPS and antithrombin binding capacity
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics.
Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Oncology, Radiology and Clinical Immunology.
Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Oncology, Radiology and Clinical Immunology, Clinical Immunology. (Biomaterialforskning)
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Materials Science.
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2006 (English)In: Colloids and Surfaces B: Biointerfaces, ISSN 0927-7765, E-ISSN 1873-4367, Vol. 49, no 1, 1-7 p.Article in journal (Refereed) Published
Abstract [en]

The durability and functionality of a heparin coating on artificial heart valve leaflets were evaluated with X-ray photoelectron spectroscopy (XPS) and by the coatings’ capacity to bind antithrombin. Current methods for accelerated life-time testing are based on exposing leaflets to water solutions. In this paper a method is explored, in which heart valve leaflets were exposed to a continuous high shear rate (4 L/min) of human citrated plasma. It was found that the heparin coating was stable and wear resistant enough to still be present after 3 weeks and to have about the same antithrombin uptake as coatings not exposed to circulating plasma. It was, however, partly destroyed by the test as found using XPS. We suggest that heparin chains from the upper layer of heparin have been torn off from the carrier chain, in combination with loss of heparin conjugate and plasma deposition in patches. This study showed that XPS provides additional information to biological measurements such as antithrombin uptake. XPS is therefore a valuable technique not only to characterize biomaterials but also to evaluate the effect of a performance test.

Place, publisher, year, edition, pages
2006. Vol. 49, no 1, 1-7 p.
Keyword [en]
Antithrombins/*chemistry/*metabolism, Biocompatible Materials/*chemistry, Carbohydrate Conformation, Carbohydrate Sequence, Electrons, Heart Valves/*chemistry/*metabolism, Heparin/*chemistry, Humans, Materials Testing, Molecular Sequence Data, Sensitivity and Specificity, Spectrum Analysis, Surface Properties, X-Rays
National Category
Chemical Sciences
Identifiers
URN: urn:nbn:se:uu:diva-94387DOI: 10.1016/j.colsurfb.2006.02.007PubMedID: 16567083OAI: oai:DiVA.org:uu-94387DiVA: diva2:168219
Available from: 2006-04-27 Created: 2006-04-27 Last updated: 2017-12-14Bibliographically approved
In thesis
1. Characterization of Surfaces Designed for Biomedical Applications
Open this publication in new window or tab >>Characterization of Surfaces Designed for Biomedical Applications
2006 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

In order to develop blood biocompatible materials a heparin surface and a phosphorylcholine (PC) functionalized polymer surface were characterized using photoelectron spectroscopy (PES). The formation of the heparin surface was studied by quartz crystal microbalance with dissipation monitoring (QCM-D). This heparin surface consists of heparin conjugates deposited on a conditioning layer, applied once or twice. The PC functionalized polymer, poly(trimethylene carbonate), was linked to a silicon substrate through 3-amino- propyltrimethoxysilane (APTMS), also studied using PES.

Synchrotron radiation based PES showed that the thicker heparin film resulted in complete coverage of the substrate, while the thinner did not. This could explain the difference in blood biocompatibility between the two films, as observed by others. It was also found that the heparin chains bend down towards the substrate (under vacuum).

For the thinner heparin film the modifications, resulting from extensive irradiation of the sample, were studied with synchrotron radiation based PES. This was done at a pressure of about 10-7 mbar and in 0.5 mbar water vapor. It was found that the modification is slower under water vapor than at low pressures and that the damaged film incorporates water upon exposure.

The heparin coating was found to be stable and wear resistant enough to still be present on artificial heart valves after three weeks testing in circulating plasma. It then had about the same antithrombin uptake as a non-tested surface. The film was, however, partly destroyed by the durability test and plasma proteins were deposited.

The PC functionalized, APTMS linked polymer was found to be much shorter than could be expected from random reactions. One plausible explanation is an interaction between the PC group and the silane surface, favoring aminolysis close to the PC group. This is consistent with our finding that the PC group bends down towards the surface.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2006. 55 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 171
Keyword
Physics, heparin, photoelectron spectroscopy, phosphorylcholine, biomaterial, quartz crystal dissipation, Fysik
Research subject
Physics
Identifiers
urn:nbn:se:uu:diva-6827 (URN)91-554-6546-3 (ISBN)
Public defence
2006-05-19, Polhemssalen, Ångströmlaboratoriet, Hus 1, Lägerhyddsvägen 1, Uppsala, 10:15
Opponent
Supervisors
Available from: 2006-04-27 Created: 2006-04-27Bibliographically approved

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Rensmo, Håkan

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