Biomaterials built by biology: Mechanism and applications of hyperbranched fractal plasmonic structures

第一部分： 非技术总结普通金属的行为随着金属尺寸的减小而发生显著变化。像金和银这样的金属，当它们变小的时候，颜色和电学性质会发生巨大的变化。人们已经利用超小金属簇的颜色变化和电学特性来制造医疗设备，环境传感器和电子元件。然而，很难在非常小的尺寸制度下控制物质。我们最近展示了微小的蛋白质片段如何实际上导致金属簇组装成更大的线状结构。这是建造人们可以使用的更大结构的关键一步。我们在这项研究中的目标是使用蛋白质片段来创建功能器件。我们将这些短的蛋白质片段与小的金属簇一起孵育。我们的初步数据表明，蛋白质充当向导，可以使金属簇自组装成中等大小的非常复杂的结构（大于源簇，但小于大块金属）。也就是说，我们正在使用蛋白质指南将微小的金属簇组装成电线。在进行对照实验以了解机制后，我们将确定这种技术的局限性，即，我们将决定我们能把电线做多大。然后，我们将使用由此产生的导线制造传感器，可以快速诊断和区分不同的呼吸道病毒。最后，我们将利用尺寸变化带来的颜色变化来培训下一代材料科学家。第二部分： 分层等离子体生物材料是令人感兴趣的，因为它们是有用的。这些生物材料是由小的纳米颗粒组成的，这些纳米颗粒联合收割机结合成更大的微米级结构。由于其独特的结构，分级等离子体生物材料具有可调的光学，电子和结构特性。这些特性可以用于医疗设备，环境传感器，电子元件等，因此，这项研究的长期目标是开发与生物构造的分层纳米粒子相关的理论和应用。更具体地说，我们的初步工作是在限定的肽序列存在下使用扩散限制聚集来构建具有分形雪花状设计的分级银生物材料（见下图）。这些分形系统由与某些短肽（5 - 20个残基）孵育的~30 nm银纳米球构建。我们现在寻求资金进行额外的研究，以获得一个连贯的机械理解的肽长度，氨基酸序列和纳米颗粒表面如何显着影响生物材料形态。我们假设，层次组装是由纳米颗粒表面肽支架之间的桥接相互作用驱动的。为了验证这一假设，目标1将研究肽长度和电荷的结构/活性关系：我们将监测作为肽设计函数的纳米颗粒形态。目标#2将扰动纳米颗粒表面化学，以阐明表面配体对颗粒组装成分级结构的作用。目标#3将通过面对面组合多种自组装来构建更大的生物材料-这项工作将导致基于DNA引导组装的定制线和网格。目标#4将这些见解用于通过简单的颜色变化区分呼吸系统疾病的实用传感器。我们还包括使用等离子体材料固有的色度变化来招募和教育新一代材料科学家的目标。因此，该项目的成果是新知识和新材料，以创造有利于社会以及新培训的材料科学家的分层等离子体生物材料。该奖项反映了NSF的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

PART 1: NON-TECHNICAL SUMMARYThe behavior of common metals changes dramatically as the size of the metal decreases. The color and electrical properties of metals like gold and silver change dramatically as they get smaller. People have used the color changes and electrical properties of ultrasmall metal clusters to make medical devices, environmental sensors, and electronic components. However, it is very difficult to control matter at very small size regimes. We recently showed how tiny protein fragments can actually cause metal clusters to assemble into larger wire-like structures. This is a key step to building larger structures that people can use. Our goal in this research is to use protein fragments to create functional devices. We will incubate these short protein fragments with small metallic clusters. Our preliminary data showed that the protein acts as a guide and can cause the metallic clusters to self-assemble into remarkably complex structures of an intermediate size (bigger than the source clusters but smaller than bulk metal). That is, we are using the protein guides to assemble tiny clusters of metals into wires. After doing controlled experiments to understand the mechanism, we will determine the limits of this technique, i.e., we will determine how big we can make the wires. We will then use the resulting wires to make a sensor that can quickly diagnose and discriminate between different respiratory viruses. Finally, we will use the color changes resulting from the sizes changes to train the next-generation of materials scientists. PART 2: TECHNICAL SUMMARYHierarchical plasmonic biomaterials are interesting because they are useful. These biomaterials are built from small nanoparticles that combine into larger micron-sized structures. As a result of their unique structure, hierarchical plasmonic biomaterials have tunable optical, electronic, and structural properties. These properties can then be harnessed for medical devices, environmental sensors, electronic components, etc. Thus, the long-term goal of this research is to develop theory and applications related to biologically-constructed hierarchical nanoparticles. More specifically, our preliminary work uses diffusion-limited aggregation in the presence of defined peptide sequences to build hierarchical silver biomaterials with a fractal snowflake-like design (see figures below). These fractal systems were constructed from ~30 nm silver nanospheres incubated with certain short peptides (5 – 20 residues). We now seek funds to conduct additional studies to derive a coherent mechanistic understanding of how the peptide length, amino acid sequence, and nanoparticle surface so dramatically impacts biomaterial morphology. We hypothesize that the hierarchical assembly is driven by bridging interactions between the nanoparticle surface the peptide scaffold. To test this hypothesis, Objective #1 will study the structure/activity relationship of the peptide length and charge: We will monitor nanoparticle morphology as a function of peptide design. Objective #2 will perturb the nanoparticle surface chemistry to elucidate the role that surface ligands have on particle assembly into hierarchical structures. Objective #3 will build even larger biomaterials by combining multiple self-assemblies face-to-face—this work will lead to customized wires and lattices based on DNA-guided assembly. Objective #4 will deploy these insights for a practical sensor that discriminates between respiratory diseases via a simple color change. We also include objectives that use the colorimetric changes inherent to plasmonic materials to recruit and educate a new generation of materials scientists. Thus, the project outcomes are new knowledge and new materials to create hierarchical plasmonic biomaterials that benefit society as well as newly trained materials scientists.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.