Functionalized Mesoporous Silica Thin Films with Different Mesostructures and Surface Modifications for Controlled Release

Mesoporous materials have been studied extensively since 1990s because of their special characters, for example, high surface area and pore volume, and tunable pore size. Up to now, mesoporous materials can be fabricated in variable morphologies such as bulk, fiber, nanoparticles, and film. This thesis includes the synthesis and application of mesoporous silica thin films.
This project took mesoporous silica thin films as drug-delivery matrix and fluorescent dye (FITC) as model drug to study the release behavior of FITC. The experimental variables include mesostructures and chemical functionalities. The mesostructures include 2D hexagonal and 3D hexagonal. The functionalizations include immersion (physical adsorption), physical doping, and cleavable binding. In addition, release model is applied to explain the release behavior. This study can reach release in a stable, long-term, and controlled release behavior at specific timing. In the future, it is potential to be the substrate of cell engineering and the device of biosensor.
In immersion, the 3D hexagonal mesostructure loaded less amount of FITC dye in the experiment of binding isotherm. Because in complex pore structure, the heaped FITC dye molecules at pore entrance produce barrier of mass transport; the barrier hinders the loading of following FITC molecules into internal pores. As a result, the loading amount decreases. In release behavior, both mesostructures show first-ordered kinetics. Because the release in governed by the diffusion inside pores and the dye molecules can diffuse freely inside pores, the mesostructures do not impact release seriously.
In physical doping, FITC dye disperses uniformly in silica framework. The release obeys zero-ordered kinetics, representing the release is governed by the dissolution of FITC dye from silica framework into PBS solution. In cleavable binding, the release includes two stages. The first-stage release is zero-ordered kinetics, and that is from the FITC molecules that do not bind to disulfide linker. The second-stage release can be controlled by adding disulfide reduce reagent to approach controlled release at precise time.