NER: Construction of Bioactive Nanoparticles and Investigation of the Relationship Between Particle Size and Enzyme Activity

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Enzymes are the catalysts that effect chemical transformations in biological world. The wide application of enzyme-based technologies is viewed as an important strategy to develop green industries that are energy-efficient and environment-benign. Immobilized enzymes, which are usually prepared by attaching enzymes to solid materials, are preferred in industries due to the ease of reuse and extended lifetime. Among other properties, the size of the solid materials is critical in determining the effective content and availability of attached enzymes. Accordingly, nano-sized particles provide the upper limits of the performance of immobilized enzymes. Currently, however, not much knowledge regarding the preparation and behaviors of bioactive nanoparticles is available. The feasibility of a unique process for the construction of enzyme-bearing nanoparticles will be examined in this research. The assumption is that enzyme molecules grafted with hydrophobic polymer chains will function as surfactants, and can selectively assemble at oil-water interfaces if applied to a microemulsion polymerization system. This mechanism will lead the enzyme to be covalently attached to the external surface of the resulted nanoparticles. In addition to the development of high performance nano biocatalysts, intent is also to shed light on mechanisms governing their catalytic behaviors. Like free enzyme molecules, nanoparticles exhibit Brownian motion. That means the attached enzymes are not immobilized, but with restrained mobility. This consideration points to an interesting transitional region bridging those of free and immobilized enzymes. Current theories appear to be difficult to cover such a transitional region. For example, the collision theory fails to provide a reliable prediction on the impact of particle size on enzyme activity. This project will probe the validity of classical theories for such size-activity relationships, thus inspire future theoretical studies regarding nano biocatalysts. Results from this study will also help to understand a much broader range of fundamental issues in other areas, such as the behaviors of aggregated proteins in biological systems, nano-size drug delivery devices, and biomedical diagnostic and drug-targeting systems.