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

酶是生物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的绿色产业的重要战略。 固定化酶通常通过将酶附着到固体材料上来制备，由于易于重复使用和延长寿命，因此在工业中是优选的。 在其他性质中，固体材料的尺寸在确定附着的酶的有效含量和可用性方面是关键的。 因此，纳米尺寸的颗粒提供了固定化酶的性能的上限。 然而，目前关于生物活性纳米颗粒的制备和行为的知识并不多。 在这项研究中，将检查一个独特的方法来构建含酶纳米颗粒的可行性。 假设是，与疏水性聚合物链接枝的酶分子将作为表面活性剂，并且如果应用于微乳液聚合体系，可以选择性地在油-水界面组装。 这种机制将导致酶共价连接到所得纳米颗粒的外表面。 除了开发高性能的纳米生物催化剂外，还旨在阐明其催化行为的机制。 与游离酶分子一样，纳米颗粒也表现出布朗运动。 这意味着附着的酶不是固定的，而是具有受限的移动性。 这一考虑指出了一个有趣的过渡区域，连接游离酶和固定化酶。 目前的理论似乎很难涵盖这样一个过渡区域。 例如，碰撞理论未能提供关于颗粒大小对酶活性的影响的可靠预测。 本计画将探讨经典理论对于这种尺寸-活性关系的有效性，进而启发未来奈米生物触媒的理论研究。 这项研究的结果也将有助于了解其他领域更广泛的基本问题，例如生物系统中聚集蛋白质的行为，纳米尺寸的药物递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.