Hyperstore: Singlet States and supercritical fluids for storage of hyperpolarised spin order / Nuclear Magnetic Resonance

核磁共振是一种用途广泛的分析工具，应用范围从基础物理到医学。在其成像模式MRI中，它提供有关解剖、新陈代谢和生物功能的信息。然而，核磁共振的灵敏度很低，这使得它的许多用途变得困难，而其他一些用途如果没有某种形式的信号增强就不可能实现。例如，核磁共振对人类癌症的代谢成像是最近引入的核自旋超极化方法才得以实现的。在这些方法中，溶解动态核极化(DDNP-本提议的核心)可以制备非常高程度的核自旋极化，可以将信噪比提高到10,000倍。然而，尽管有这种巨大的增强，体内应用仍然处于可行性的边缘，因为增强的极化的寿命相对较短。例如，癌症新陈代谢的超极化核磁共振图像的空间分辨率受到超极化物质运输和提纯过程中信号损失的影响。因此，对后超极化协议的改进，允许超极化材料的传输，将改进新兴技术，并开辟新的研究和应用领域。拟议的研究将解决三个相互关联的主要障碍：超极化材料缺乏纯度(超极化技术需要电子自由基)；超极化磁化的寿命有限(自由基的存在和许多其他内在因素使核自旋极化随时间衰减，这一机制称为自旋弛豫)；极化设备的流动性有限(溶解-DNP设备昂贵且笨重，超极化试剂的寿命有限，使得无法将试剂运送到很长的距离。因此，使用点仅限于生产点附近)。为了克服这些障碍，我们将使用超临界CO2层析来快速高效地纯化超极化材料。由于自旋极化存储时间与粘度大致成反比，而且超临界二氧化碳的粘度比传统溶剂低10-30倍，因此我们还将在超临界二氧化碳下存储纯化材料，潜在地将存储时间延长5-10倍。然后，我们将探索通过使用长寿命状态和在液氮下冻结超极化溶液，冻结分子运动，从而将弛豫损失降至最低，从而进一步延长储存时间。我们的目标是将超极化材料的存储时间延长到两个小时以上，增加生产地点和使用地点之间的距离。我们还打算建造一种方便和便携的运输装置，使超极化材料能够在不超过50%的极化损失的情况下远距离运输(在实现的最大寿命允许的情况下)。

Nuclear magnetic resonance (NMR) is a versatile analytical tool with applications ranging from basic physics to medicine. In its imaging mode, MRI, it provides information on anatomy, metabolism and biological functions. However, NMR has low sensitivity, making many of its uses difficult and others impossible without some form of signal enhancement. For example, metabolic imaging of human cancer by MRI was only made possible by the recent introduction of nuclear spin hyperpolarisation methods. Among these methods, dissolution dynamic nuclear polarisation (dDNP - central to this proposal) prepare a very high degree of nuclear spin polarisation that can increase the signal-to-noise ratio up to 10,000 times. However, despite this enormous enhancement, in-vivo applications remain on the borderline of feasibility because of the relatively short lifetime of the enhanced polarisation. For example, the spatial resolution of hyperpolarised MRI images of cancer metabolism is compromised by the loss of signal during transport and purification of the hyperpolarised material. Improvements to post-hyperpolarisation protocols, allowing transport of hyperpolarised material, would therefore improve emerging techniques and open up new areas of research and applications. The proposed research will address three interconnected main obstacles: the lack of purity of the hyperpolarised material (electron radicals are required by the hyperpolarisation technique); the limited lifetime of hyperpolarised magnetisation (the presence of radicals and many other intrinsic factors make nuclear spin polarisation to decay over time, a mechanism know as spin relaxation); the limited mobility of the polarising equipment (dissolution-DNP equipment is expensive and bulky and the limited lifetime of the hyperpolarised agents makes it impossible to transport the agent for significant distances. The point-of-use is therefore confined to the near vicinity of the point-of-production). In order to overcome these obstacles we will use supercritical-CO2 chromatography to rapidly and efficiently purify the hyperpolarised material. Because spin polarisation storage times are roughly inversely proportional to viscosity, and because supercritical-CO2 has a viscosity 10-30 times lower than that of conventional solvents, we will also store the purified material under supercritical-CO2, potentially extending the length of storage time by 5-10 times. We will then explore extending storage time further by using long-lived states and by freezing the hyperpolarised solution under liquid nitrogen, freezing molecular motion and therefore minimising relaxation losses. We aim to extend storage of hyperpolarised material to over two hours, increasing distance between the point-of-production and the point-of-use. We also intend to build a convenient and portable transport device to enable transport of hyperpolarised material over long distances (as allowed by maximum lifetime achieved) with loss of no more than 50% of polarisation.