A new ultra-low field in-vivo EPR technology for biomedical applications

描述(申请人提供)：体内EPR最成功的应用是对氧、一氧化氮、生物药物、pH和氧化还原状态的非侵入性测量，应用于肿瘤学、心脏病学、神经科学和毒理学。由于与传统高频检测方案相关的基本限制，这些研究仅在小范围的受试者中进行。当前一代的EPR系统通常使用GHz或更高频率(L、X、Q频段)来实现所需的分辨率。有几个关键因素使得人体在高频下的在体EPR方法非常困难，主要的因素是对可测量系统的大小和形状的限制，以及与生物系统吸收高水平射频有关的安全问题。我们将开发一种新的超低场在体EPR光谱仪系统，该系统对人体使用安全，具有高灵敏度和良好的穿透深度。这种新设备将克服与传统高频EPR相关的限制，但仍能使SNR比现有技术提高100至1000倍。我们将通过采用我们实验室开发的两项最先进的技术来实现这一目标：(1)新的微波超导量子干涉装置(MSQUID)(2)无低温超导梯度仪系统。在5 MHz的低功率射频激励下运行，将完全消除与有限穿透深度和样品加热相关的问题。我们的目标是：1)利用新型混合SQUID读出系统，在室温下使用顺磁样品(例如自旋探针)演示M级EPR信号检测(包括连续波和脉冲方法)。1b)使用相同的检测系统演示核磁共振信号检测，同时考虑到混合核磁共振/电子顺磁共振波谱系统。2)使用大视场探测线圈的无制冷剂冷却系统，使用适合于人体研究的参数来展示EPR波谱性能。3)演示在生理相关浓度下检测和测量生物系统中的电子顺磁共振。3A。使用小球藻的活悬浮液，我们将试图检测在黑暗条件下预期的电子自旋共振，并检测和量化光合作用过程中发生的ESR增加。这些技术目标构成了将先进技术应用于人类使用的基础。随着临床设备的长期目标，我们还将进行有限的人体测试。我们的目标3B是进行活体人体实验，以检测剧烈运动时自由基浓度的增加。我们的最终目标是创造一种在不影响灵敏度和信号质量的情况下，从安全性、成本、选址和复杂性的角度出发，实用的人体活体生物医学EPR装置。 与公共卫生相关(由申请人提供)：自由基在人类疾病中发挥重要作用，如硫酸铁中毒、电离辐射、高压氧治疗早产儿的氧毒性、紫外线辐射诱发癌症，以及很可能在帕金森氏症、阿尔茨海默氏症和其他神经退行性疾病中的作用。电子顺磁共振(EPR)是一种非侵入性的检测和测量化学和生物体系中自由基的光谱技术，已被用于体内EPR测量氧、一氧化氮、生物药物、pH和氧化还原状态，在肿瘤学、心脏病学、神经学和毒理学中有应用。到目前为止，由于常规高频检测方案的基本技术和安全限制，这些研究仅在小范围的受试者中进行。我们建议开发一种新的超低频EPR方法，使用最先进的磁通量传感器，以实现安全、经济有效和实用的在体EPR人类，最终能够同时进行核磁共振测量。

DESCRIPTION (provided by applicant): The most successful uses of in vivo EPR have been non-invasive measurement of oxygen, nitric oxide, bioradicals, pH and redox state, with applications in oncology, cardiology, neuroscience and toxicology. These studies have been performed only in small size subjects due to fundamental limitations associated with the traditional high-frequency detection scheme. Current generation EPR systems typically use GHz or higher frequencies (L-, X-, Q- band) to achieve the required resolution. There are several key factors, which make in vivo EPR methods of human body at high frequencies extremely difficult, the principal ones being limits on the size and shape of the systems that can be measured and safety issues related to the absorption of high-level RF by biological systems. We will develop a new ultra-low field in vivo EPR spectrometer system that is safe for use in humans and has high sensitivity and good penetration depth. The new device will overcome the limitations associated with conventional EPR at high frequencies yet still achieve 100 to 1000 fold improved SNR over existing technology. We will achieve this goal by employing two state- of-the-art technologies developed in our lab: (1) a new microwave superconducting quantum interference device (MSQUID) (2) a cryogen-free, superconducting gradiometer system. Operation at 5MHz with a low power RF excitation will completely eliminate the problems associated with finite penetration depth and sample-heating. Our aims are: 1A) Demonstrate ?M-level EPR signal detection (both CW and pulse methods) using paramagnetic samples (e.g. spin probes) at room temperature using cryogenic detection with the new hybrid SQUID readout system. 1B) Demonstrate the NMR signal detection using the same detection system, with hybrid NMR/EPR spectroscopy systems in mind. 2) Use a cryogen-free cooling system with a large field-of-view detection coil to demonstrate EPR spectroscopy performance, using parameters suitable for the human study. 3) Demonstrate detection and measurement of electron paramagnetic resonance in biological systems at physiologically relevant concentrations. 3A. Using living suspensions of Chlorella pyroidenosa, we will attempt to detect the expected electron spin resonance under dark conditions, and to detect and quantify the ESR increase that occurs during photosynthesis. These technical aims form the foundations for the application of the advanced technology to human use. With the long term goal of a clinical device, we will also perform limited human testing. Our aim3B is to perform in vivo human experiments to detect increased free radical concentration during intense exercise. Our ultimate objective is to create a device for human in vivo biomedical EPR that is practical from the perspectives of safety, cost, siting and complexity, without compromising sensitivity and signal quality. PUBLIC HEALTH RELEVANCE (provided by applicant): Free radicals play a major role in human diseases such as iron sulfate poisoning, ionizing radiation, oxygen toxicity in premature infants treated with hyperbaric oxygen, ultraviolet radiation-induced cancer and very likely in Parkinson's, Alzheimer's and other neurodegenerative disorders. Electron paramagnetic resonance (EPR) is a non-invasive spectroscopic technique to detect and measure free radicals in chemical and biological system that has been applied in- vivo EPR to measure oxygen, nitric oxide, bioradicals, pH and redox state, with applications in oncology, cardiology, neurology and toxicology. To date, these studies have been performed only in small size subjects due to fundamental technical and safety limits of the conventional high-frequency detection scheme. We propose here to develop a novel ultra low-frequency EPR approach using a state-of-the-art magnetic flux sensor to enable safe, cost- effective and practical in vivo EPR humans, with an instrument ultimately capable of simultaneous NMR measurement.