Preparation Of Silica-Based Mesoporous Materials For Sample Preparation

Mesoporous silica materials have been identified as potential candidates for sample preparation due to their unique characteristics of large surface area, tunable pore structure, controllable wall composition, modifiable surface property, as well as good stability. Functionalized silica-based mesoporous materials have found a great utility in different domains in sample preparation including extraction of metal ions, adsorption of organic compounds, size selective enrichment of peptides/proteins and so on. However, the operation formats with silica-based mesoporous materials as adsorbents for sample preparation are still limited. Simplication, expeditiousness and miniaturization are trends of development of extraction techneques. Discoveries on new types of silica-based mesoporous materials or novel supports for immobilization of silica-based mesoporous materials can benefit the establishment of new extraction formats.In this dissertation, novel silica-based mesoporous materials are prepared as adsorbents for development of easy-operation, rapid and miniaturized extraction formats for sample preparation.1. The development of silica-based mesoporous materials is reviewed. It emphasizes on the functionalization of silica-based mesoporous materials and their applications in sample preparation.2. Pseudomorphic synthesis were successfully applied to preparation of magnetic mesoporous silica microspheres (Fe3O4@mSiO2), which possess good monodispersion, high magnetization, superparamagnetism, uniform accessible mesopores, and large surface area and pore volume. With these good properties, Fe3O4@mSiO2 spheres were applied to the rapid enrichment of peptides. The magnetic separation property made the extraction process rapid. Compared with magenitic amorphous silica, Fe3O4@mSiO2 had higher enrichment efficiency of peptides, due to its larger surface area. The size-exclusion effect benefit from the uniform mesopors made Fe3O4@mSiO2 effectively exclude high-Mw proteins and selectively enrich peptides simultaneously.3. A general strategy was developed to prepare powdered-material embedded pipette tips. With this simple method, mesoporous silica microspheres embedded pipette tip (mSiO2-Tip) was successfully fabricated for the first time. The mSiO2-Tip can be used for rapid (within 2 min), selective, sensitive and cost-effective enrichment of peptides from complex biological samples.4. Using electrospinning combined with pseudomorphic synthesis, ordered mesoporous silica fiber (OMSF) was prepared on a large scale for the first time. OMSF possessed uniform accessible mesopores, large surface area and pore volume and had continuously long fibrous property. With these unique properties, a simple in-syringe solid phase extraction approach (In-Syringe SPE) using OMSF as the adsorbent was developed to perform plasma peptide enrichment in less than 3 min without any electrical device, which can be used for rapid on-site peptidomic sampling.5. With electrospun silica fibers as adsorbents, a novel in-syringe dispersive SPE method (In-Syringe dSPE) combining the advantages of packed SPE (pSPE) and dSPE was developed for the first time. Benefiting from the vortex assisted dispersion and the sub-microscale structure of the electrospun fibers, the extraction equilibrium can be accomplished within 1 min. The In-Syringe dSPE method was demonstrated to be rapid (within 4 min), high-throughput (36-syringe plate), easy to operate (without centrifugation), cost-effective and solvent-saving. The excellent performance in microextraction of endogenous cytokinins suggested that this miniaturized SPE format was sensitive and reproducible for dealing with a small amount of sample.6. A simple method was developed for the preparation of ordered mesoporous silica-carbon composite fibers (OMSCFs). The OMSCFs exhibited high carbon content, continuously long fibrous properties, uniform accessible mesopores, and a large surface area. The OMSCFs were also found to have ion-exchange capacity. On the basis of the size-exclusion effect of the mesopores and mixed-mode hydrophobic/ion-exchange interactions, the OMSCFs were applied for rapid enrichment of endogenous peptides by using In-Syringe dSPE. The adsorption mechanism was studied, and the eluting solution was optimized with standard peptide/protein solutions and protein digests. Employing a successive three-step elution strategy, followed by LC-MS/MS analysis, led to excellent performance with this approach in the extraction and prefractionation of peptides from human serum.