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Theses and Dissertations

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Browsing Theses and Dissertations by Subject "biomaterials"

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    The development of hyaluronan enhanced expanded polytetrafluoroethylene and linear low density polyethylene for blood contacting applications
    (Colorado State University. Libraries, 2019) Bui, Hieu T., author; James, Susan, advisor; Reynolds, Melissa, committee member; Popat, Ketul, committee member; Olver, Christine, committee member
    Cardiovascular disease is the number one cause of death in high income, industrialized countries. Designing cardiovascular implants from synthetic polymers is a cost-effective solution to the growing demand for medical treatments such as heart valve replacements and cardiovascular bypass procedures. Synthetic polymers are often known for their tunability, durability, and low production cost. Unfortunately, these materials are also prone to induce thrombosis. Therefore, improving the blood compatibility of these polymers is still a major challenge in the biomedical field. This dissertation discusses the alteration of two synthetic polymers, linear low density polyethylene (LLDPE) and expanded polytetrafluoroethylene (ePTFE), using hyaluronan (HA) to improve their blood compatibility. HA, a naturally occurring polysaccharide in the human body, is known for its wound healing and anticoagulant properties. In this work, two unique methods were developed for HA enhancement of ePTFE (HA-ePTFE) and LLDPE (HA-LLDPE). This was a process driven research that aimed at designing HA-ePTFE and HA-LLDPE by analyzing the effect of different treatment parameters on the properties of the resultant materials. In the case of ePTFE, it was demonstrated that HA can be incorporated into vascular ePTFE grafts by exploiting the micro pores of the polymer and adjusting the spraying treatment. In the HA-LLDPE fabrication process, its parameters were varied to assess their effects on the interpenetrating polymer network (IPN) formation. Surface characterization such as water contact angle goniometry, infrared spectroscopy, and toluidine blue O (TBO) staining prove that HA treatment successfully changed the surface chemistry and increased the hydrophilicity of ePTFE and LLDPE. Thermal analysis and gas chromatography-mass spectrometry were used to quantify the effects of different treatment conditions on material properties. Tensile properties such as elastic modulus, tensile strength, yield stress and ultimate strain are unchanged by HA enhancement for both polymers. The biological results reveal that HA-ePTFE and HA-LLDPE are not cytotoxic and result in less blood clotting and platelet activation than ePTFE and LLDPE.
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    ItemOpen Access
    Titania nanotube arrays: interfaces for implantable devices
    (Colorado State University. Libraries, 2012) Smith, Barbara Symie, author; Popat, Ketul, advisor; Gonzalez-Juarrero, Mercedes, committee member; Prasad, Ashok, committee member; Dasi, Lakshmi Prasad, committee member; Dow, Steven, committee member
    For the 8-10% of Americans (20-25 million people) that have implanted biomedical devices, biomaterial failure and the need for revision surgery are critical concerns. The major causes for failure in implantable biomedical devices promoting a need for re- implantation and revision surgery include thrombosis, post-operative infection, immune driven fibrosis and biomechanical failure. The successful integration of long-term implantable devices is highly dependent on the early events of tissue/biomaterial interaction, promoting either implant rejection or a wound healing response (extracellular matrix production and vasculature). Favorable interactions between the implant surface and the respective tissue are critical for the long-term success of any implantable device. Recent studies have shown that material surfaces which mimic the natural physiological hierarchy of in vivo tissue may provide a possible solution for enhancing biomaterial integration, thus preventing infection and biomaterial rejection. Titania nanotube arrays, fabricated using a simple anodization technique, provide a template capable of promoting altered cellular functionality at a hierarchy similar to that of natural tissue. This work focuses on the fabrication of immobilized, vertically oriented and highly uniform titania nanotube arrays to determine how this specific nano-architecture affects skin cell functionality, hemocompatibility, thrombogenicity and the immune response. The results in this work identify enhanced dermal matrix production, altered hemocompatibility, reduced thrombogenicity and a deterred immune response on titania nanotube arrays. This evidences promising implications with respect to the use of titania nanotube arrays as beneficial interfaces for the successful implantation of biomedical devices.