Repository logo

Theses and Dissertations

Permanent URI for this collection

https://hdl.handle.net/10217/100353

Browse

Browsing Theses and Dissertations by Subject "antibacterial"

Now showing 1 - 2 of 2
  • Thumbnail Image
    ItemOpen Access
    Antibacterial effects of sputter deposited silver-doped hydroxyapatite thin films
    (Colorado State University. Libraries, 2011) Trujillo, Nathan Anthony, author; Popat, Ketul, advisor; Williams, John, advisor; Reynolds, Melissa, committee member; Crans, Debbie, committee member
    Over recent years, researchers have studied innovative ways to increase the lifespan of orthopedic implants in order to meet the soaring demand of hip and knee replacements. Since many of these implants fail as a result of loosening, wear, and inflammation caused by repeated loading on the joints, coatings such as hydroxyapatite (HAp) on titanium with a unique topography have been shown to improve the interface between the implant and the natural tissue. Other serious problems with long-term or ideally permanent implants are bacterial colonization. It is important to prevent initial bacterial colonization as existing colonies have potential to become encased in an extracellular matrix polymer (biofilm) which is resistant to antibacterial agents. The following work considers the potential of etching using plasma based ion implantation and ion beam sputter deposition to produce hydroxyapatite thin films on etched titanium doped with silver as an antibacterial component. Plasma-based ion implantation was used to examine the effects of pre-etching on plain titanium. Topographical changes to the titanium samples were examined and compared via scanning electron microscopy. It was determined that plasma-based ion implantation at -700eV could etch titanium to produce similar topography as ion beam etching in a shorter processing time. Hydroxyapatite and silver-doped hydroxyapatite thin films were then sputter deposited on titanium substrates etched at -700eV. For silver-doped films, two concentrations of silver (~0.5wt% and ~1.5wt%) were used. Silver concentrations in the film were determined using energy dispersive x-ray spectroscopy. Film thicknesses were determined by measuring the surface profile using contact profilometry. Staphylococcus epidermidis (SE) and Pseudomonas aeruginosa (PA) adhesion studies were performed on plain titanium, titanium coated with hydroxyapatite, titanium coated with ~0.5 wt% silver-doped hydroxyapatite, and titanium coated with ~1.5wt% silver-doped hydroxyapatite. It was discovered during the study that the films were delaminating from the samples thus killing bacteria in suspension. Release studies performed in addition to adhesion confirmed that the silver-doped films prevented SE and PA bacterial growth in suspension. To prevent delamination, the films were annealed by heat treatment in air at a temperature of 600°C. X-ray diffraction confirmed the presence of a crystalline hydroxyapatite phase on each sample type. Films were immersed in PBS at 37°C and remained in incubation for four weeks to determine there was no delamination or silver leaching.
  • Thumbnail Image
    ItemOpen Access
    Evaluation of nitric oxide releasing polymers for wound healing applications
    (Colorado State University. Libraries, 2015) Wold, Kathryn A., author; Reynolds, Melissa, advisor; Henry, Charles, committee member; Kipper, Matt, committee member; Popat, Ketul, committee member; Williams, John, committee member
    Chronic, non-healing wounds afflict millions of Americans and represent a costly burden to the healthcare industry. In addition, the overuse and misuse of antibiotics has triggered the widespread emergence of drug-resistant bacteria, making the treatment of infected wounds more challenging. As a result, improved methods for wound care incorporating antibiotic-alternative bactericidal agents are in high demand. Recent wound care advances have focused on the development of dressings incorporating physical structures and biological components which mimic those encountered in a natural wound environment. Nitric oxide (NO), an endogenously produced molecule upregulated to promote cellular function and bactericidal activity during wound healing, has been harnessed in material systems and studied for wound healing potential. This work describes the characterization, bactericidal activity, cell functionality and processing of two NO-releasing polymer systems, one water-soluble and another water-insoluble. The results of this work demonstrate the capability of these polymeric NO-releasing materials to promote high log reductions of planktonic bacteria. Additionally, polymer dosages that promote cell survival and induce cytotoxicity in eukaryotic cells have been determined and nano-scale polymer fibers that maintain NO release properties have been processed. These results represent qualities beneficial towards the development of enhanced materials for the treatment of chronic infected wounds.