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Theses and Dissertations

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Browsing Theses and Dissertations by Subject "biomaterials"

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    Characterization of osseointegrative phosphatidylserine and cholesterol orthopaedic implant coatings
    (Colorado State University. Libraries, 2013) Rodgers, William Paul, author; James, Susan, advisor; Popat, Ketul, committee member; Ehrhart, Nicole, committee member; De Long, Susan, committee member
    Total joint arthroplasties/replacements are one of the most successful surgeries available today for improving patients’ quality of life. By 2030 in the US, demand for primary total hip and knee arthroplasties are expected to grow by 174% and 673% respectively to a combined total of over 4 million procedures performed annually, driven largely by an ageing population and an increased occurrence of obesity. Current patient options for load-bearing bone integrating implants have significant shortcomings. Nearly a third of patients require a revision surgery before the implant is 15 years old, and those who have revision surgeries are at an increased risk of requiring additional reoperations. A recent implant technology that has shown to be effective at improving bone to implant integration is the use of phosphatidylserine (DOPS) coatings. These coatings are challenging to analyze and measure due to their highly dynamic, soft, rough, thick, and optically diffractive properties. Previous work had difficulty investigating pertinent parameters for these coating’s development due in large part to a lack of available analytical techniques and a dearth of understanding of the micro- and nano-structural configuration of the coatings. This work addresses the lack of techniques available for use with DOPS coatings through the development of original methods of measurement, including the use of scanning white light interferometry and nanoindentation. These techniques were then applied for the characterization of DOPS coatings and the study of effects from several factors: 1. the influence of adding calcium and cholesterol to the coatings, 2. the effect of composition and roughness on aqueous contact angles, and 3. the impact of ageing and storage environment on the coatings. This project lays a foundation for the continued development and improvement of DOPS coatings, which have the promise of significantly improving current patient options for bone integrating implants. Using these newly developed and highly repeatable quantitative analysis methods, this study sheds light on the microstructural configuration of the DOPS coatings and elucidates previously unexplained phenomena of the coatings. Cholesterol was found to supersaturate in the coatings at high concentration and phase separate into an anhydrous crystalline form, while lower concentrations were found to significantly harden the coatings. Morphological and microstructural changes were detected in the coatings over the course of as little as two weeks that were dependent on the storage environment. The results and understanding gained pave the path for focused future research effort. Additionally, the methods and techniques developed for the analysis of DOPS coatings have a broader application for the measurement and analysis of other problematic biological materials and surfaces.
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    Hemocompatibility of hyaluronan enhanced linear low-density polyethylene for heart valve leaflet applications
    (Colorado State University. Libraries, 2018) Simon-Walker, Rachael, author; Popat, Ketul C., advisor; Reynolds, Melissa, committee member; Orton, Christopher, committee member; Chicco, Adam, committee member
    Heart valve disease is a major concern in both developed countries with advanced ageing populations and undeveloped countries which experience a high incidence of rheumatism leading to valvular disease. To reduce mortality and improve quality of life, heart valve implantations have been widely used to assist in improving function of the native cardiovascular system. While mechanical heart valves and tissue-based heart valves have been successfully used to improve quality of life compared to untreated valvular disease, draw-backs are inherent. Mechanical heart valves are prone to thrombosis and require life-long supplemental anti-coagulation therapy. Tissue-based valves are more hemocompatible, but lack the durability required for long-term implantation. To address these issues, polymeric heart valves have been highly sought after due to polymers' abilities to enhance durability and be manufactured to be similar to the native heart valve leaflet. In addition, their surfaces can be modified to increase hemocompatibility. In this work we explore the hemocompatibility and immune response to a novel polymer for use in heart valve leaflet applications; hyaluronan enhanced linear low-density polyethylene. It is proposed that the combination of linear low-density polyethylene with hyaluronan will create a highly durable material that will reduce thrombosis and inflammation due to the anionic and hydrophilic nature of the glycosaminoglycan.