Doctor of Philosophy (PhD)
The development of biocompatible polymers using thiol-acrylate Michael addition reactions between not only acrylates and thiols but also between amines and acrylates were demonstrated. The synthesis of an in situ tertiary amine catalyst initiates the propagation steps of the polymerization process by subsequently reacting with trimethylolpropane tris (3-mercaptopropionate) (TMPTMP). A few notable characteristics of this reaction are tunable gel times, the capability of reaching high polymer conversion and suitable mechanical strength. With addition of hydroxyapatite to the polymeric phase and foaming, a porous bone composite was produced. Further osteogenisis and in vivo work using the PETA-co-TMPTMP (HA) composite material was analyzed. The PETA-co-TMPTMP-co-TMTMP with 20%HA showed an increase in osteogenic potential higher than the FDA approved PCL over the 21-day study. The rats did not exhibit any severe systemic responses from the polymer implant, and an increase in bone growth was observed for the rats containing PETA-co-TMPTMP (HA) samples compared to the rat containing no polymer. An antimicrobial study on the PETA-co-TMPTMP polymer was also performed by adding silver nanoparticles to the PETA-co-TMPTMP polymer to provide an antimicrobial component to the already well-established bone replacement polymer. By coating the polymer in a silver containing solution and adding 20%excess thiol to the polymer, it was effective at reducing common bacteria. While the application of the PETA-co-TMPTMP polymer has proven to be effective for osteogenic bone scaffolds, the reason a material without cell adhesive moieties supported stem cell growth remained elusive. The next study used polyethylene glycol diacrylate (PEGDA) and trimethylolpropane ethoxylated triacrylate (TMPeTA) to understand the relationship between thiol-acrylate polymers and cell adhesion. Wettability, modulus, and degradation stability were all tested, and it was observed that these properties play a role in the adhesion to these materials. As per live/dead staining, cell morphology changed to spindle shape on the lower molecular weight, 692 TMPeTA samples whereas the 912 TMPeTA’s cell morphology remained the same. Cell adhesion on the TMPeTA(692) polymer versus the TMPeTA(912) is likely due to the 692 polymer yielding an overall tighter crosslinked network, and it’s contact angle falling in the range for not being too hydrophilic/hydrophobic.
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Garber, Leah Alyce, "Biomedical Applications of Thiol-Acrylate Polymers" (2016). LSU Doctoral Dissertations. 1498.
Pojman, John A