Development of New Atomic-Based EPR Spin Probes

摘要/摘要电子顺磁共振（EPR）方法在医学中的应用是一个快速发展的领域。在过去的十年中已经取得了重大进展，EPR可能很快就会用于指导癌症、中风和对氧合和缺氧进行无创测量至关重要的疾病的治疗。然而，进一步改进以提高其检测活性氧（ROS）产生的自由基的敏感性将使其适用于更广泛的疾病。生物医学EPR系统的一个关键组成部分是自旋探针，它是检测顺磁自由基所必需的基本化学试剂。然而，目前的自旋探针有局限性。例如，当前一代的自旋探针不够灵敏，无法直接检测或成像帕金森病、阿尔茨海默病等与年龄相关的疾病或ROS介导的疾病中活性氧在体内的产生。为了克服这些限制，我们建议研究新的自旋探针基于顺磁原子封装在富勒笼。含有未配对电子的原子，如固定在对称C60笼中心的氮原子，完全不与外界物质反应，产生前所未有的窄线宽。例如，N@C60具有已知最窄的EPR线宽度之一，使其检测效率比当前化合物高100到1000倍。除了保护被封装的原子外，富勒烯笼还可以与自由基相互作用，并且在N@C60表面发生的反应会产生可测量的EPR谱偏移。这些特性，加上已证实的生物相容性，使富勒烯封装的原子成为理想的自旋探针。N@C60是理想的自旋探针的缩影，但由于其批量生产和纯化困难，目前对其的研究受到阻碍。然而，原子N并不是富勒烯封装的唯一可能选择。我们已经研究了具有类似EPR特性的替代原子，但商业化生产要容易得多。本项目的具体目的是合成和表征这些候选化合物中最有前途的，并证明它可以构成一种新型EPR自旋探针的基础，与现有化合物相比具有许多优势。

DESCRIPTION (provided by applicant): Development of New Atomic-Based EPR Spin Probes Summary/Abstract The use of electron paramagnetic resonance (EPR) methods in medicine is a rapidly advancing field. There has been significant progress in the past decade, and EPR may soon be used to guide the treatment of cancer, strokes, and conditions where it is crucial to make non-invasive measurements of oxygenation and hypoxia. However, further improvements to increase its sensitivity to detect radicals generated by reactive oxygen species (ROS) would make it applicable to a wider range of diseases. A key component of the biomedical EPR system is the spin probe, the fundamental chemical agent necessary to detect paramagnetic radicals. However, current spin probes have limitations. For example, the current generation of spin probes are not sensitive enough to directly detect or image the in vivo generation of reactive oxygen species in age related disorders or diseases mediated by ROS such as Parkinson's and Alzheimer's disease. To overcome these limitations, we propose to investigate new spin probes based upon paramagnetic atoms encapsulated in fullerene cages. Atoms containing unpaired electrons, such as atomic nitrogen pinned at the center of the symmetric C60 cage, are completely protected from reaction with external species and produce unprecedented narrow line widths. For example, N@C60 has one of the narrowest known EPR line widths, giving it a detection efficiency 100 to 1000 times better than the current compounds. In addition to protecting the encapsulated atom, the fullerene cage can interact with radical species, and reactions occurring on the surface of N@C60 produce measurable shifts in its EPR spectrum. Such features, along with proven biological compatibility, make fullerene-encapsulated atoms ideal spin probes. N@C60 epitomizes the ideal spin probe, but research on it is currently hindered by difficulties in producing and purifying it in bulk. However, atomic N is not the only possible choice for fullerene encapsulation. We have examined alternative atoms that will have similar EPR properties, but will be far easier to produce commercially. The specific aim of this project is to synthesize and characterize the most promising of these candidates and demonstrate that it can form the basis for a new type of EPR spin probe with many advantages over the current compounds. PUBLIC HEALTH RELEVANCE: Electron paramagnetic resonance (EPR) is an emerging technique similar to magnetic resonance imaging (MRI) that has the potential to help diagnose and guide the treatment of diseases such as cancer, stroke, and other conditions involving disruption of reactive oxygen species (ROS) homeostasis. EPR relies upon molecular agents called spin probes to interact with nearby oxygen or reactive oxygen radicals to generate a detectable signal. However, new compounds with higher sensitivity are needed to improve EPR technology and allow it to be used for more diseases. To remove the limitations inherent to current spin probes, we propose to investigate new types of spin probes based upon paramagnetic atoms encapsulated in C60 fullerenes that will have higher sensitivity in their ability to detect reactive oxygen species. The development of new spin probes that allow in vivo detection of ROS produced, for example, by Parkinson's and other ROS diseases would represent a significant advance in biomedical EPR technology.