ERA_Chemistry_Biomimetic formation and organization of magnetite nanoparticles

一维磁性纳米结构由于具有较强的单轴形状各向异性，其磁性能优于非组织材料。趋磁细菌中的磁小体链代表了这种磁铁的生物学范例，在称为磁小体的细胞器中合成了尺寸可控的磁铁矿晶体，并排列成线性链。因此，生物材料显示出一种难以与合成材料相匹配的分层结构。在这个项目中，我们的目标是应用微生物所使用的设计原则，通过两种不同的方法，沿着生物模板生长一维磁性纳米结构。1)我们将在烧杯中合成大小可控的磁性纳米颗粒，然后将这些纳米颗粒排成线性链。特别是，我们将使用生物添加剂，这些添加剂在我们的实验室中被证明是体外晶体尺寸的强大控制器，以形成大量胶体稳定的磁铁矿纳米颗粒。这种添加剂起到粘合剂的作用，将前体纳米颗粒组装在一起，最终形成中晶。2)我们将利用重组表达的丝状蛋白，这些蛋白具有周期性重复的生物识别位点，对溶液中的铁或纳米颗粒具有很强的亲和力。因此，长丝将作为形成磁铁矿纳米纤维的模板。我们将使用先进的高分辨率透射电子显微镜（TEM）技术，包括低温透射电子显微镜和电子全息成像，来表征成核和组装过程，以及产品的磁性能。这个项目将为更好地理解纳米尺度上的中晶形成铺平道路。此外，我们预计我们的研究结果将成为一维磁性纳米结构的纳米和生物医学应用的起点。

One-dimensional magnetic nanostructures have magnetic properties superior to non-organized materials due to a strong uniaxial shape anisotropy. Magnetosome chains in magnetotactic bacteria represent a biological paradigm of such a magnet, where magnetite crystals of controlled dimensions are synthesized in organelles called magnetosomes and are arranged into linear chains. The biological materials thus display a hierarchical architecture that is hardly matched by synthetic materials. In this project, we aim at applying the design principles used by the microorganisms to grow one-dimensional magnetic nanostructures along biological templates, using two different approaches.1) We will synthesize magnetic nanoparticles of controlled size in the beaker and then assemble these nanoparticles in linear chains. In particular, we will use biological additives that were shown in our labs to be powerful controllers of crystal dimensions in vitro to form a large amount of colloidally stable magnetite nanoparticles. The additive serves as a glue to assemble precursor nanoparticles that eventually form a mesocrystal. 2) We will utilize recombinantly expressed filamentous proteins with periodically repeated biological recognition sites that have either strong affinity to bind iron from solution or to attach to nanoparticles. The filament will thus serve as a template for the formation of magnetite nanofibers.We will use advanced high-resolution transmission electron microscopy (TEM) techniques, including cryo-TEM and electron holography, to characterize the nucleation and assembly process, as well as the magnetic properties of the products.This project will pave the way towards a better understanding of mesocrystal formation at the nanoscale. In addition, we anticipate that the outcomes of our research will be the starting points towards nano- and biomedical applications of 1D magnetic nanostructures.