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

第1部分：非技术性总结随着金属尺寸的减小，普通金属的行为会发生巨大的变化。金和银等金属的颜色和电学性质随着它们变小而发生巨大变化。人们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，在非常小的区域内控制物质是非常困难的。我们最近展示了微小的蛋白质片段是如何真正导致金属簇组装成更大的线状结构的。这是建造人们可以使用的更大建筑的关键一步。我们在这项研究中的目标是使用蛋白质片段来创造功能设备。我们将用小的金属簇孵化这些短的蛋白质片段。我们的初步数据显示，蛋白质起到了引导作用，可以使金属团簇自组装成中等大小的非常复杂的结构(大于源团簇，但小于主体金属)。也就是说，我们正在使用蛋白质导向器将微小的金属簇组装成导线。在做了受控实验以了解这一机制后，我们将确定这项技术的极限，即我们将确定我们可以制造多大的电线。然后，我们将使用产生的电线制造一种传感器，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产生的颜色变化来培训下一代材料科学家。技术综述分级等离子体生物材料之所以有趣，是因为它们很有用。这些生物材料是由小的纳米颗粒结合成更大的微米级结构制成的。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、电子和结构性质。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建的分层纳米颗粒相关的理论和应用。更具体地说，我们的初步工作是在定义的多肽序列存在的情况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)。这些分形体系是由~30 nm的银纳米球与某些短肽(5-20个残基)孵育而成的。我们现在寻求资金进行更多的研究，以得出一个连贯的机制理解如何肽长度、氨基酸序列和纳米颗粒表面如此显著地影响生物材料的形态。我们假设，层次化组装是由纳米颗粒表面和多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将研究多肽长度和电荷的结构/活性关系：我们将监测纳米颗粒的形态作为多肽设计的函数。目的#2将扰乱纳米粒子的表面化学，以阐明表面配体在粒子组装成分级结构中所起的作用。目标#3将通过面对面组合多个自组装来构建更大的生物材料--这项工作将导致基于DNA引导组装的定制导线和晶格。目标#4将把这些见解运用到一种实用的传感器上，通过简单的颜色变化来区分呼吸道疾病。我们还包括利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，项目成果是创造分级等离子体生物材料的新知识和新材料，造福于社会和新培训的材料科学家。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势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.