Coating Effects on MR Relaxivities: Dendron-Iron Oxide Nanoparticle Models

描述(申请人提供)：揭示氧化铁纳米团簇的表面结构和磁共振弛豫度之间的关系是提高这类造影剂的对比特异度和扩大适用范围的关键。氧化铁纳米颗粒的表面性质对决定颗粒弛豫特性的整体磁性有很大的影响。由于配位球不完整，磁性金属阳离子的化学环境在氧化铁表面的对称性降低，纳米粒子表面的性质通常与体内纳米粒子的性质不同。随着纳米粒子尺寸的减小，由于粒子内部表面原子比例的增加，表面相互作用对纳米粒子磁性能的影响变得更加显著。此外，涂层属性可以调节水分子的表面访问、颗粒流体动力学尺寸、翻滚速率、溶解度、微尺度聚集、组织摄取和/或细胞内分配。然而，由于缺乏一个模型系统来有力地控制其表面和核心特性，关于表面结构参数和氧化铁纳米颗粒弛豫度之间关系的详细研究仍然有限。我们相信，树枝状保护的氧化铁纳米粒子可以发展成一种新的模型，系统地研究表面效应对磁共振弛豫性能的影响。树枝状化合物的合成将以受控、确定和离散的方式实现传统的多步有机合成。树枝状氧化铁纳米粒子的壳层结构可以被精确地构建和调节。此外，由于树枝状涂层的存在，树枝状氧化铁纳米粒子是一类独特的造影剂，与传统造影剂相比具有许多潜在的优势。例如，当静脉注射树突时，基于树突的血液渗漏到其他身体隔室的可能性可以通过改变树突的分子质量、覆盖率和功能来调节。我们的领域(R15)拨款申请设定了两个具体目标：(1)开发构建具有各种表面静电和其他性质的树枝状覆盖的氧化铁纳米颗粒的新途径；(2)研究树枝状氧化铁纳米颗粒在块状和蜂窝环境中的核磁共振弛豫诱导特性，特别是关于影响的问题。我们相信，这笔中等规模的R15赠款将是对一个没有受到MR社区太多关注的重要领域的高价值投资。

DESCRIPTION (provided by applicant): Uncovering the relationship between the surface structure and magnetic resonance relaxivities of iron oxide nanoclusters is key to improving the contrast specificity and expanding applicability of this class of contrast agents. The surface properties of iron oxide nanoparticles have enormous effects on the overall magnetic characteristics that determine the particles' relaxation properties. The symmetry at the iron oxide surface is reduced for the chemical surroundings of magnetic metal cations due to the incomplete coordination sphere, and properties of the nanoparticle surfaces are usually different from those within the body nanoparticle. As the size of nanoparticles decreases, the influence of surface interactions magnetic properties of the nanoparticles becomes more significant due to the increased fraction of surface atoms within the particle. Additionally, the coating properties can modulate surface access of water molecules, the particle hydrodynamic size, tumbling rate, solubility, microscale clustering, tissue uptake, and/or intracellular partitioning. However, due to the lack of a model system that has vigorous controls of both its surface core characteristics, detailed investigations of the relationships between structural parameters surface and the relaxivities of iron oxide nanoparticles are still limited. We believe that dendron protected iron oxide nanoparticles can be developed into a novel model for systematically the surface effects on MR relaxation properties. The synthesis of dendrons will be achieved conventional multiple-step organic syntheses in a controlled, defined, and discrete manner. structure of the shell coatings of dendron-iron oxide nanoparticles can be precisely constructed regulated. In addition, due to their dendron coatings, dendron-iron oxide nanoparticles unique class of contrast agents offering many potential advantages over conventional counterparts. For example, when injected intravenously, the leakage of dendron-based the bloodstream into other bodily compartments can potentially be tuned by varying the molecular weight, coverage, and functionality of the dendrons. Our AREA (R15) grant application has set up two specific aims: (1) developing new routes for constructing dendron-coated iron oxide nanoparticles that have various surface electrostatics and other properties; and (2) examining the NMR relaxation-inducing properties dendron-iron oxide nanoparticles in bulk and cellular environments, particularly regarding effects. We believe that this medium-sized R15 grant would be a high-value investment for an important area that has not received much attention from the MR community.