It is widely accepted that the initial event that significantly influences biocompatibility is the nearly instantaneous adsorption of proteins from biological fluids onto the biomaterial surface. For blood-contacting devices, the complex layer of adsorbed plasma proteins is generally unfavourable and leads to major complications, including thrombus formation, inflammatory tissue responses, and microbial infections. Furthermore, protein interaction with passive films on metallic biomaterial surfaces may contribute to enhanced in vivo corrosion. To gain a better understanding of this phenomenon, the present thesis investigated the fundamental aspects of the interaction of the serum protein fibrinogen with a medical-grade stainless steel 316LVM surface using electrochemical and IR spectroscopy techniques. Aspects of this interaction included the thermodynamics and kinetics of fibrinogen adsorption, the effect of fibrinogen adsorption on the corrosion behavior of 316LVM stainless steel, and the conformational changes of fibrinogen upon its adsorption onto the stainless steel surface. / It was shown that fibrinogen readily adsorbs onto the 316LVM stainless steel surface. Increases in the bulk protein concentration resulted in a corresponding increase of the surface coverage, a dependence that was described by the Langmuir isotherm. Large, negative values of the calculated Gibbs energy of adsorption indicated a highly spontaneous and strong adsorption of fibrinogen onto the 316LVM stainless steel at all investigated temperatures. Although the adsorption process was shown to be endothermic under the applied experimental conditions, the primary driving force for the adsorption process was found to be the positive entropy gain that arises from structural loss and/or rearrangement of the protein upon adsorption, as well as dehydration of the protein and stainless steel surface during the adsorption process. Kinetic measurements indicated that fibrinogen adsorption occurs rapidly. / It was determined that for short contact times (1 hour), the addition of fibrinogen to the electrolyte enhanced the corrosion rate of the 316LVM stainless steel at the open circuit potential. For longer contact times (24 hours), an increase in the polarization resistance values was obtained, indicating an enhanced corrosion resistance of the material. It was postulated that the protein was not capable of complexing the well-stabilized passive film, and instead remained adsorbed to form a protective barrier to diffusion of oxygen-containing species from the electrolyte to the stainless steel surface. / The secondary structure of the surface-adsorbed fibrinogen molecules was investigated by modeling the experimental PM-IRRAS spectra. It was shown that the protein lost a certain extent of its secondary structure upon adsorption to the steel surface. Fibrinogen molecules adsorbed from more dilute solutions were also shown to possess a lower alpha-helical content than those adsorbed from more concentrated solutions, suggesting they laid on the stainless steel surface in a more linear configuration.
| Identifer | oai:union.ndltd.org:LACETR/oai:collectionscanada.gc.ca:QMM.99757 |
| Date | January 2007 |
| Creators | Desroches, Marie-Josée. |
| Publisher | McGill University |
| Source Sets | Library and Archives Canada ETDs Repository / Centre d'archives des thèses électroniques de Bibliothèque et Archives Canada |
| Language | English |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Format | application/pdf |
| Coverage | Master of Engineering (Department of Chemical Engineering.) |
| Rights | © Marie-Josée Desroches, 2007 |
| Relation | alephsysno: 002614142, proquestno: AAIMR32585, Theses scanned by UMI/ProQuest. |
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