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

酶是生物世界中影响化学转化的催化剂。酶技术的广泛应用被视为发展节能环保绿色产业的重要战略。固定化酶通常是通过将酶附着在固体材料上而制备的，由于其易于重复使用和延长寿命而在工业中受到青睐。在其他性质中，固体材料的大小对决定结合酶的有效含量和可用性至关重要。因此，纳米颗粒提供了固定化酶性能的上限。然而，目前关于生物活性纳米颗粒的制备和行为的知识还不是很多。在这项研究中，一种独特的构建含酶纳米粒的工艺的可行性将被检验。假设在微乳液聚合体系中，接枝了疏水高分子链的酶分子可以起到表面活性剂的作用，并且可以选择性地聚集在油水界面。这种机制将导致酶以共价方式附着在所得到的纳米颗粒的外表面上。除了开发高性能的纳米生物催化剂外，还打算阐明其催化行为的机制。与游离酶分子一样，纳米粒子也表现出布朗运动。这意味着附着的酶不是固定的，而是具有受限的流动性。这一考虑指向了一个有趣的过渡区，连接了游离酶和固定化酶的过渡区。目前的理论似乎很难涵盖这样一个过渡地区。例如，碰撞理论未能对颗粒大小对酶活性的影响提供可靠的预测。本项目将探索这种尺寸-活性关系的经典理论的有效性，从而启发未来关于纳米生物催化剂的理论研究。这项研究的结果也将有助于理解更广泛的其他领域的基本问题，如生物系统中聚集蛋白的行为，纳米药物输送装置，以及生物医学诊断和药物靶向系统。

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.