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Scholarly Works (4 results)

  • Thesis
  • Peer Reviewed
UC Riverside Electronic Theses and Dissertations (2018)

Bioresorbable cardiovascular scaffold (BCS) is promising to eliminate the chronic complications caused by the conventional permanent scaffold by being completely absorbed in the body. Magnesium (Mg) as a bioresorbable metal has attracted considerable attention for BCS. However, Mg must be modified to achieve a slower degradation rate and to induce a desired endothelial cell response to prevent neointimal hyperplasia and endothelium abnormality. To address these challenges, the present dissertation developed polymer-based surface modifications, including different polymer coatings and nanopatterned polymer coatings, to enhance the overall performances of Mg. The first part of the dissertation is a comparative investigation of four representative biodegradable plastics as coating materials, including poly(L-lactic acid), two different poly(lactic-co-glycolic acid), and polycaprolactone. No previous literature thoroughly compared their functionality as coating materials for Mg. It was found that all four polymer coatings slowed the degradation of Mg, and PLGA (50:50) coating promoted the adhesion and spreading of human endothelial cells the most. The second part of the research explored the potential of a novel bioresorbable elastomer, poly(glycerol sebacate) (PGS), as an ideal coating material for Mg. The work verified the effectiveness of PGS coating in reducing the degradation rate of Mg and provided the first reference in the existent literature about the in vitro performances of PGS coatings on Mg. The third part of the dissertation pioneered novel nanopatterned polymer coatings on Mg. The nanopatterns are promising to further enhance the functionality of polymer coatings as a nonbiological and nondrug approach. For the first time, the parallel groove nanopatterns have been successfully fabricated on the PLGA (50:50) coatings and PGS coatings respectively. The nanopatterns on PLGA (50:50)-coated Mg presented a highly-effective biofunction to control the elongation of human endothelial cells without using any biological molecule or drug. The effort established an effective method to control endothelial cell activities on bioresorbable Mg. Overall, the entire dissertation provided extensive knowledge regarding polymer coatings and nanopatterned polymer coatings as surface modification methods for Mg towards desired performances for cardiovascular applications.

    Cover page: Polymer-Based Surface Modification of Bio-Resorbable Magnesium for Cardiovascular Applications
    • Article
    • Peer Reviewed
    UC Riverside Previously Published Works (2017)
    Magnesium (Mg) alloys are promising materials for biodegradable implants, but their clinical translation requires improved control over their degradation rates. Proteins may be a major contributing factor to Mg alloy degradation, but are not yet fully understood. This article reports the effects of fetal bovine serum (FBS), a physiologically relevant mixture of proteins, on Mg and Mg alloy degradation. FBS had little impact on mass loss of pure Mg during immersion degradation, regardless of whether or not a native oxide layer was present on the sample surface. FBS reduced the mass loss of Mg-Yttrium (MgY) alloy with an oxidized surface during immersion degradation, but increased the mass loss for the same alloy with a metallic surface (surface oxides were removed). FBS also influenced the mode of degradation by limiting the depth of pit formation during degradation processes on commercially pure Mg with metallic or oxidized surfaces and on MgY alloy with oxidized surfaces. The results demonstrated that serum proteins had significant interactions with Mg-based biodegradable metals, and these interactions may be modified by alloy composition and processing. Therefore, proteins should be taken into account when designing experiments to assess degradation of Mg-based implants.
      Cover page: The Effects of Serum Proteins on Magnesium Alloy Degradation in Vitro
      • Article
      • Peer Reviewed
      UC Riverside Previously Published Works (2017)
      Nanomaterials such as nanostructured surfaces, nanoparticles, and nanocomposites represent new viable sources for future therapeutics for cardiovascular diseases. The special properties of nanomaterials such as their intrinsic physiochemical properties, surface energy and surface topographies could actively enhance desirable cellular responses within the cardiovascular system, projecting a growing potential for clinical translation. Recent progress on nanomaterials opened up new opportunities for treating cardiovascular diseases. Successful translation of nanomaterials into cardiovascular applications requires a comprehensive understanding of both nanomaterials and biomedicine, and, thus, it is critical to stress current advancements on both sides. In this review, the authors introduced crucial fabrication techniques for promising nanomaterials for cardiovascular applications. This review highlighted the key elements to consider for their fabrication, properties and applications. The important concerns relevant to cardiovascular nanomaterials, such as cellular responses to nanomaterials and the toxicity of nanomaterials, are also discussed. This review provided an overview of necessary knowledge and key concerns on nanomaterials specific for treating cardiovascular diseases, from the perspectives of both material science and biomedicine.
        Cover page: Nanomaterials for treating cardiovascular diseases: A review
        • Article
        • Peer Reviewed
        UC Riverside Previously Published Works (2019)
        A portable device was designed and constructed for studying the properties of biomaterials in physiologically relevant fluids under controllable flow conditions that closely simulate fluid flow inside the body. The device can fit entirely inside a cell incubator; and, thus, it can be used directly under standard cell culture conditions. An impedance-driven pump was built in the sterile flow loop to control the flow rates of fluids, which made the device small and portable for easy deployment in the incubator. To demonstrate the device functions, magnesium (Mg) as a representative biodegradable material was tested in the flow device for immersion degradation under flow versus static conditions, while the flow module was placed inside a standard cell incubator. The flow rate was controlled at 0.17 ± 0.06 ml/s for this study; and, the flow rate is adjustable through the controller module outside of incubators for simulating the flow rates in the ranges of blood flow in human artery (0.05 ∼0.43 ml/s) and vein (0.02 ∼0.08 ml/s). Degradation of Mg under flow versus static conditions was characterized by measuring the changes of sample mass and thickness, and Mg2+ ion concentrations in the immersion media. Surface chemistry and morphology of Mg after immersion under flow versus static conditions were compared. The portable impedance-driven flow device is easy to fit inside an incubator and much smaller than a peristaltic pump, providing a valuable solution for studying biomaterials and implants (e.g. vascular or ureteral stents) in body fluids under flow versus static conditions with or without cells.
          Cover page: A portable device for studying the effects of fluid flow on degradation properties of biomaterials inside cell incubators
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