| dc.description.abstract | Extracorporeal membrane oxygenation (ECMO) machines are used for critically ill patients who are afflicted by respiratory or cardiac complications. During prolonged operation, surface contact between human blood and the tubing in these machines can trigger an immune response, activating the intrinsic pathway for blood clot formation. Commercially available, coated Tygon tubing often used with these machines aims to prevent these occlusions from forming through the timed release of anti-coagulants or the use of biocompatible layers. A recent trend is to use polymeric materials to change the hydrophilicity of the surface of the Tygon. This thesis details the development of a chemical process to create a superhydrophilic surface to repel surface-activating proteins to prevent hemocoagulation. Commercially available, unmodified Tygon was exposed to an aminosilane that absorbs into the polymer surface, crosslinks, and functionalizes the surface with a layer of free amines. The surface of free amines was then exposed to an acyl bromide to provide initiator sites for the subsequent polymerization step. This initiator-laden surface was then exposed to a solution of zwitterionic monomer to provide chain-wise growth of hydrophilic polymer chains via a surface-initiated polymerization process known as activators regenerated by electron transfer, atom transfer radical polymerization (ARGET ATRP). These polymer chains are designed to attract and hold ambient water molecules from the blood to form a hydration layer, which would repel blood proteins. Optimization of the process was extensive with each step altering time, temperature, reactant concentrations, and reactant species. Characterization of the resulting polymer revealed that a uniform, hydrophilic layer was formed along the surface of the Tygon tubing while maintaining the beneficial physical properties of Tygon, such as transparency and flexibility. Coagulation testing is currently being performed in collaboration with contributors from the Vanderbilt Medical Clinic to determine if the polymer layer is able to slow the cascade of the intrinsic pathway. | |
