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Protein Fouling in Vascular Implants Madeline Lok, Matthew Rakochey, Gillian McKercher, Michael Mislan Schulich School of Engineering, University of Calgary. Group 18. Vascular Implants. Clot Formation.
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Protein Fouling in Vascular Implants Madeline Lok, Matthew Rakochey, Gillian McKercher, Michael Mislan Schulich School of Engineering, University of Calgary Group 18 Vascular Implants Clot Formation • Vascular implants are medical devices used to treat cardiovascular diseases like Atherosclerosis or Aneurysm • Stents are used to hold open vessels which have become blocked to allow blood flow • Grafts are used to replace vessels which have become nonviable • Implants can fail as a result of blood clot formation caused by blood-material interactions • Blood-material interactions can lead to the formation of blood clots by two mechanisms • Contact activation occurs when factor FXII comes into contact with a negatively charged surface and changes shape • Platelet activation occurs when Fibrinogen adsorbs to a hydrophobic surface and platelets adhere to the vessel wall Protein Adsorption Implant Biomaterials • Adsorption is a physical process where a molecule comes into contact with a surface and adheres to it • Proteins are biomolecules composed of Amino Acids. Their properties and function depends on their composition and structure • Protein adsorption is influenced by three main factors • Charge: A charge gradient can favour adsorption and change the shape of a protein • Hydrophobicity: Hydrophobic groups on the protein will not react with the aqueous solution but will irreversibly bond with other hyrdophobic surfaces • Other Non-covalent Interactions: These include intermolecular forces such as Van der Waals, Hydrogen bonding and ionic bonds The success and durability of a vascular implant is extremely dependent on the chosen material. There are six major factors influencing the selectivity of a material: • Interaction with Water • Drug Elution • Surface Charges and Chemical Structure • Stability • Physical Structure • Result in Clinical Trials While the listed thromboresistent characteristics are important, a material’s success in clinical trials is the ultimate determining factor for its production in practical therapy.e-PTFE (like Gore-Tex), for example, performed better than PEO and is thus produced for implants. Preferable over