Evaluating mesoporous materials for potential drug delivery and catalytic applications

Abstract

Mesoporous silica nanoparticles (MSN) have attracted significant attention in the past decade due to their unique properties such as high surface area, tunable pore size, large pore volume, controllable particle morphology and ease of surface functionalization. They have been extensively researched for their application as a potential targeted drug delivery carrier. Some research has also focussed on developing MSN-based hard templating strategies for the synthesis of other mesoporous materials such as mesoporous carbon nanoparticles (MCN) with diverse properties. In order to safely employ MSN as a drug delivery vehicle, considerations in hemocompatibility become essential and critical. The research presented in this dissertation demonstrates the effects and interaction of various morphologies of MSN on human RBC membrane at biologically relevant concentrations. The addition of organic functionality on the surface of these MSNs has been known to produce profound effects on their interaction with the human RBC membrane. The effects of two types of lipid bilayer coatings on the surface of MSN with the human RBC membrane have been systematically investigated. It has been demonstrated that a small change in the composition of the lipid bilayer coating on the MSN surface can transform the MSN-based drug delivery system from being seriously incompatible to being largely hemocompatible. The utility of MSN can be further enhanced by using it as a hard template for the synthesis of other mesoporous nanomaterials such as MCN. Herein, large-pore mesoporous silica nanoparticles (l-MSN) have been utilized for the development of monodispersed MCN with high surface areas and well-defined morphology. The morphology can be tuned by making small changes in the reaction parameters. Furthermore, a highly selective covalent surface functionalization approach for the modification of MCN has been developed for tethering functional groups and single-site catalysts on the surface of MCN. A copper-based single-site catalyst covalently anchored on the surface of MCN has been demonstrated to be highly active for organic transformation such selective benzyl alcohol oxidation under environmentally benign conditions. The surface modification strategy for MCN has been furthered exploited to anchor platinum-based single-site catalysts on its surface. For the first time, these MCN-based heterogenous catalysts have been used for the electrochemical oxidation of methane at low temperature (80°C) in a proton exchange membrane fuel cell demonstrating unprecedented activities. In general, the fundamental studies on hemocompatibility and the development of MSN as a platform for the synthesis of monodispersed MCN with its selective surface modification approach will not only bring new insights for the application of MSN as an intravascular drug-delivery vehicle but also assist in the design of novel MCN-based systems templated from MSN for catalytic, electrocatalytic and biological applications.