Protein Fouling in Vascular Implants

1. 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