Browsing by Subject "Microenvironment"
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Item Dynamic photo-tunable hydrogels for temporal modulation of matrix mechanical properties(2014-12) Stowers, Ryan Scott; Suggs, Laura J.; Bonnecaze, Roger T; Brock, Amy L; Stachowiak, Jeanne C; Van Den Berg, CarlaThe extracellular matrix is highly influential in regulating cell fate and function in vivo. Biophysical cues from the microenvironment are involved in nearly every cellular phenomenon, from initial embryogenesis to diseases such as atherosclerosis and cancer. This dissertation seeks to develop 3D hydrogel models to more accurately recapitulate the in vivo microenvironment by allowing for temporal modulation of stiffness. A strategy is presented to spatially and temporally tune the mechanical properties of 3D alginate-based hydrogels using a light-triggered mechanism. This approach is demonstrated to be cytocompatible and highly tunable. The system is employed to elucidate the morphological response of fibroblasts to stiffening 3D environments. Additionally, the platform is translated to an in vivo application of transdermal gel modulation. Finally, the phototunable hydrogels are used to evaluate the effect of matrix stiffening on breast epithelial cells in a mechanical environment that mimics tumor stiffening. Changes in the mechanical properties of the gel induce phenotypic changes to MCF10A epithelial cells, including collective cell migration from the mammary acini. This system is broadly applicable to the biomaterials community and could shed light on a number of outstanding biological questions.Item The behavior and separation of polystyrene in mixed solvent systems(2009-05-15) Hamilton, Patrick NealNon-polar phase selective solubility of modified poly(4-n-alkylstyrene) supports can be measured using fluorescent dyes as catalyst surrogates with thermomorphic and latent biphasic systems. By modifying the solvent compositions in heptane/ethanol and heptane/N, N-dimethylacetamide, increased non-polar phase selective solubility of modified polystyrene supports can be attained. Likewise, by varying the structure and length of the pendant alkyl chain, an increase in non-polar phase selective solubility is measured. These heptane soluble polymer supports can be useful for applications involving heptane soluble polymer-bound reagents and catalysts. Various polar and non-polar polymer supports were synthesized with an attached solvatochromic catalyst surrogates to determine the solvent accessibility of the supported species in pure and mixed solvents. The results of these studies indicate that in pure solvents, the influence of both polar and non-polar polymer supports on the solvent microenvironment of these polymer-supported probes is minimal. In mixed solvent systems, a polymer-like solvent microenvironment is measured in solvent mixtures comprised of solvents the polymer has unfavorable interactions. Poly(4-n-alkylstyrene) and internally functionalized polyisobutylene supports are two such polymer supports that exhibit this behavior. For terminally functionalized polymers in mixed solvents, the solvatochromic behavior does not indicate a collapsed structure. In mixed solvents, there is minimal influence of the polymer support on the solvent microenvironment of these terminally functionalized polymers. The application of soluble polyisobutylene supported copper complexes in the ATRP polymerization of styrene was investigated. Using the difference in solubility of the product polystyrene and the polyisobutylene copper complex in heptane, a solid/liquid separation of the soluble copper complex from the solid product was achieved. The results of these polymerizations indicate that the polyisobutylene copper complex behaves exactly like a low molecular weight copper complex in terms of control over molecular weight and molecular weight distribution. After the polymerizations, the polyisobutylene complexes could be separated as a heptane solution and recycled in multiple polymerizations of styrene.