Cheng-Yu Lai

Real-time imaging of tunable adenosine 5-triphosphate release from an MCM-41-type mesoporous silica nanosphere-based delivery system.

We studied a mesoporous silica nanosphere (MSN) material with tunable release capability for drug delivery applications. We employed luciferase chemiluminescence imaging to investigate the kinetics and mechanism of the adenosine 5-triphosphate (ATP) release with various disulfide-reducing agents as uncapping triggers. ATP molecules were encapsulated within the MSNs by immersing dry nanospheres in aqueous solutions of ATP followed by capping of the mesopores with chemically removable caps, such as cadmium sulfide (CdS) nanoparticles and poly(amido amine) dendrimers (PAMAM), via a disulfide linkage. By varying the chemical nature of the “cap” and “trigger” molecules in our MSN system, we discovered that the release profiles could indeed be regulated in a controllable fashion.

Fine-tuning the degree of organic functionalization of mesoporous silica nanosphere materials via an interfacially designed co-condensation method

A synthetic method that can fine tune the amount of chemically accessible organic functional groups on the pore surface of MCM-41 type mesoporous silica nanosphere (MSN) materials has been developed by electrostatically matching various anionic organoalkoxysilanes with the cationic cetyltrimethylammonium bromide micelles in a base-catalyzed condensation reaction of tetraethoxysilane.

Reversible binding and fluorescence energy transfer between surface-derivatized CdS nanoparticles and multi-functionalized fluorescent mesoporous silica nanospheres

Abstract A MCM-41 types of Mesoporous Silica Nanosphere material ( MSN ) covalently anchored with a fluorescent dye (Texas Red™) is synthesized. The Texas-Red-doped MSNs is also functionalized with a second organic group, i.e., mercaptopropyl or aminopropyl functionalities. These organic groups of the resulting bifunctional MSN s are utilized as reversible linkers to entrap two corresponding surface-derivatized cadmium sulfide ( CdS ) nanoparticles. The kinetics of encapsulation and release as well as the photophysical properties of the photoluminescent quantum dots and the MSN composites are investigated by examining the fluorescence resonance energy transfer between the two species. We demonstrated that the fluorescence energy transfer between CdS and Texas Red molecules can be “ switched off” by chemically cleaving the covalent linkage between the mesopore-entrapped CdS and the fluorescent MSN . Our results indicated that these MSN materials provided with proper pore-surface functional groups could serve as reversible hosts to entrap and release surface-derivatized cadmium sulfide nanoparticles.

Chapter 5:Enzyme Immobilization on Mesoporous Silica Supports

The applications of porous silica in biocatalysis involve enzyme (biocatalyst) immobilization on solid supports, which integrates enzymatic catalysis with heterogeneous catalysis. In this chapter, the authors outline recent advances in the area of mesoporous silica involved in enzyme immobilization development. Mesoporous silica supports provide a set of highly attractive features toward overcoming enzyme stability drawbacks both in biotechnology and biocatalysis applications. Mesoporous silica materials are structurally robust, chemically stable over a broad pH and temperature range, and benefit from flexible synthetic conditions that enable tailoring of their properties for a plethora of host–guest chemistry applications. The large surface area and the tunable pore sizes make them suitable for accommodating large biomolecules, including enzymes.

Nanostructures Viewed through Low Voltage Electron Microscopy

Materials that present nanostructural features, either internally—as in nanoporous structures, or externally—as in nanoparticles with various shapes and aspect ratios, pose a challenge in visualizing their nanoscale features via low-voltage microscopy. The LV EM 5, the only benchtop TEM in the market, offers a variety of tools that overcome the typical low voltage drawbacks. These enhancements will be presented in the context of two projects. The first part of the presentation will discuss the use of LV EM 5 in SEM-mode in a project targeting the application of mesoporous silica nanomaterials in carbon capture, with emphasis on the particles analysis. In the second part, the TEM and SEM modes will be presented in the context of a solar research project, where the solar device is fabricated solely through solution processing and both nanoparticle precursors and films are subjected to microscopy investigation.