DOI
https://doi.org/10.25772/5RHA-E366
Defense Date
2012
Document Type
Dissertation
Degree Name
Doctor of Philosophy
Department
Engineering
First Advisor
Kenneth J Wynne
Abstract
Contact antimicrobials for use in the medical device industry are being studied extensively to minimize the risk of hospital acquired infections, which are among the top ten leading causes of death in the US. Surfaces modified with quaternary ammonium containing side chains have been known to demonstrate excellent antimicrobial properties. Prior work has indicated that polyurethane surfaces with copolyoxetane soft blocks consisting of fluorinated and quaternary ammonium side chains can act as good antimicrobials. However, stabilizing the positive charge on the surface has been a challenge. The dissertation is aimed at creating a surface modifier that would confer a stable contact kill antimicrobial surface at very low modifier content, that is, less than 2 wt%. To achieve this objective, the study explored the introduction of a different fluorous group in the soft block to enhance stability. In particular, prior studies by other groups and early work by Kurt have shown that replacement of one of the terminal “chaperone” C-F bonds by C-H decreased surface tension. This led to the hypothesis that a –CF2H terminated “chaperone” group would be “amphiphilic” resulting in surface stability under both dry and wet conditions. Keeping this hypothesis in mind, a –CF2-CF2H (4F) terminal “chaperone” group was created in a modifier having two different 4F to quaternerary C12 ratios. It was found that polyurethanes prepared with a 66:34 ratio of 4F:C12 as the diol, performed as a very good surface modifier with high zeta potentials over a long period of time compared to the –CF3 based modifier. Antimicrobial tests performed within one week and four weeks after coating preparation have provided promising results that demonstrate improved biocidal stability. Guided by improved antimicrobial properties obtained with surface modifier polyurethanes made from P[(4F)(C12)-66:34-Mn], a new concept was explored by end-capping the same diol with isocyanatopropyltriethoxysilane and blending the end-capped diol with base polyurethane along with a 10 wt % cross linker. These modifiers show excellent antimicrobial properties (100% kill of bacteria) over one month with no observable changes in the zeta potential or surface morphologies. XPS analysis confirms the presence of quaternary ammonium on the surface. Preliminary kinetic studies show excellent antimicrobial properties for a 2 wt% modifier and 100% kill within 1 hr.
Rights
© The Author
Is Part Of
VCU University Archives
Is Part Of
VCU Theses and Dissertations
Date of Submission
December 2012