Overhauser Enhanced Magnetic Resonance Imaging (OMRI)

合理的探头设计：动态核极化(DNP)是一种尖端技术，利用核磁共振(NMR)/磁共振成像(MRI)显著提高了分子的检测灵敏度。这种方法可以使用核磁共振实时成像体内的动态代谢状态。为了扩大靶向代谢反应，需要开发外源的，即人工设计的DNP-核磁共振分子探针；然而，由于缺乏既定的设计指南，遵守实用的DNP-核磁共振分子探针的要求是具有挑战性的。在这里，我们报道了Ala-[1-(13)C]Gly-D2-NMe2作为DNP-核磁共振分子探针用于体内检测氨基肽酶N的活性。我们通过精确的结构研究、计算、生化评估和先进的分子设计，合理地开发了这种探针，以实现对体内酶活性的快速和可检测的响应。利用所制备的探针，我们成功地检测到了体内的酶活性。本报告提出了一种通过结构导向的分子设计来开发人工衍生的、实用的DNP-核磁共振分子探针的综合方法。低成本超极化器：研究了在屏蔽使能的排列转移(SABRE-SHETH)中通过可逆交换进行的信号放大，以实现[1-(13)C]丙酮酸的(13)C1自旋的快速超极化，使用仲氢作为核自旋有序的来源。丙酮酸与Ir极化转移络合物的交换可以通过温度和DMSO与H2O的共连接之间的灵敏相互作用来调节。通过限制[1-(13)C]丙酮酸在较低温度下的化学交换，催化剂结合的[1-(13)C]丙酮酸的有序性(13)C(50%)在不到30 S的时间内实现。在催化剂结合的丙酮酸上，用1.4T核磁共振谱仪测量了39%的极化，并在原位堆积结束时外推到50%。当使用20 mM二甲基亚砜和0.5M水时，30 mm丙酮酸盐样品的最高极化测量为13%，包括游离和结合的丙酮酸。有效的(13)C极化也可以通过亚微特斯拉磁场中良好的驰豫动力学来实现，正如与T1自旋驰豫速率相比的快速极化累积速率所表明的那样(例如，对于6 mm催化剂-[1-(13)C]丙酮酸盐样品，分别约为0.2 S(-1)和约0.1 S(-1))。最后，通过循环温度和/或优化水量，可以快速释放催化剂结合的超极化[1-(13)C]丙酮酸，为通过相对快速和简单的军刀鞘方法生产超极化[1-(13)C]丙酮酸的未来生物医学应用铺平道路。仲氢发生器：我们报告了一种使用液氮作为冷却剂的坚固且低成本的仲氢发生器设计。发电机的核心由充满催化剂的螺旋铜管组成，可以加压到35个大气压。利用顺磁性水合氧化铁催化剂，在77K时，利用三台几乎相同的发电机，可获得48%的对氢馏分。通过台式核磁共振波谱在苍蝇身上进行对氢的量化，以监测来自残留的正氢的信号-对氢是核磁共振沉默的。这种实时定量方法也被用来评估在高达1.0标准升/分钟的流量下的催化剂活性。报道的这种廉价的装置可用于使用仲氢作为核自旋超极化来源的广泛研究。为此，我们在许多临床试验中证明了这种仲氢发生器用于浓缩丙酮酸钠的超极化，丙酮酸钠是一种正在研究的代谢造影剂。报道的军刀鞘(通过可逆交换屏蔽进行信号放大使排列转移到异核)的试点优化在临床相关磁场为1T时产生了14,000倍以上的(13)C信号增强，相当于大约1.2%的(13)C极化--如果使用近100%的仲氢，报告值将增加两倍至3.5%的(13)C极化。使用D2O的磁共振成像标记物：目的：水是许多生化途径的底物。全身性给药的重水(D2O)会导致重水掺入核酸、碳水化合物、蛋白质和脂质中。考虑到它们相对较高的增殖率和由此产生的氚丰度，我们假设通过氚磁共振可以更容易地从健康组织中区分肿瘤。方法：我们在两种携带人结直肠癌(HT-29)或胰腺癌(MiaPaca2)的异种移植小鼠模型上开始给予D2O。结果：移植瘤在体内生长14天，D2O系统标记7天后，移植瘤与正常组织的dMRI对比清晰。结论：我们的新的临床相关标记成像方法使非放射性敏感的肿瘤检测成为可能，并支持在癌症成像中使用氚。

Rational Probe Design: Dynamic nuclear polarization (DNP) is a cutting-edge technique that markedly enhances the detection sensitivity of molecules using nuclear magnetic resonance (NMR)/magnetic resonance imaging (MRI). This methodology enables real-time imaging of dynamic metabolic status in vivo using MRI. To expand the targetable metabolic reactions, there is a demand for developing exogenous, i.e., artificially designed, DNP-NMR molecular probes; however, complying with the requirements of practical DNP-NMR molecular probes is challenging because of the lack of established design guidelines. Here, we report Ala-[1-(13)C]Gly-d2-NMe2 as a DNP-NMR molecular probe for in vivo detection of aminopeptidase N activity. We developed this probe rationally through precise structural investigation, calculation, biochemical assessment, and advanced molecular design to achieve rapid and detectable responses to enzyme activity in vivo. With the fabricated probe, we successfully detected enzymatic activity in vivo. This report presents a comprehensive approach for the development of artificially derived, practical DNP-NMR molecular probes through structure-guided molecular design. Low cost hyperpolarizer: Signal Amplification By Reversible Exchange in SHield Enabled Alignment Transfer (SABRE-SHEATH) is investigated to achieve rapid hyperpolarization of (13) C1 spins of [1-(13) C]pyruvate, using parahydrogen as the source of nuclear spin order. Pyruvate exchange with an iridium polarization transfer complex can be modulated via a sensitive interplay between temperature and co-ligation of DMSO and H2 O. Order-unity (13) C (50 %) polarization of catalyst-bound [1-(13) C]pyruvate is achieved in less than 30 s by restricting the chemical exchange of [1-(13) C]pyruvate at lower temperatures. On the catalyst bound pyruvate, 39 % polarization is measured using a 1.4 T NMR spectrometer, and extrapolated to 50 % at the end of build-up in situ. The highest measured polarization of a 30-mM pyruvate sample, including free and bound pyruvate is 13 % when using 20 mM DMSO and 0.5 M water in CD3 OD. Efficient (13) C polarization is also enabled by favorable relaxation dynamics in sub-microtesla magnetic fields, as indicated by fast polarization buildup rates compared to the T1 spin-relaxation rates (e. g., approximately 0.2 s(-1) versus approximately 0.1 s(-1) , respectively, for a 6 mM catalyst-[1-(13) C]pyruvate sample). Finally, the catalyst-bound hyperpolarized [1-(13) C]pyruvate can be released rapidly by cycling the temperature and/or by optimizing the amount of water, paving the way to future biomedical applications of hyperpolarized [1-(13) C]pyruvate produced via comparatively fast and simple SABRE-SHEATH-based approaches. Parahydrogen generator: We report on a robust and low-cost parahydrogen generator design employing liquid nitrogen as a coolant. The core of the generator consists of catalyst-filled spiral copper tubing, which can be pressurized to 35 atm. Parahydrogen fraction 48% was obtained at 77 K with three nearly identical generators using paramagnetic hydrated iron oxide catalysts. Parahydrogen quantification was performed on the fly via benchtop NMR spectroscopy to monitor the signal from residual orthohydrogen-parahydrogen is NMR silent. This real-time quantification approach was also used to evaluate catalyst activation at up to 1.0 standard liter per minute flow rate. The reported inexpensive device can be employed for a wide range of studies employing parahydrogen as a source of nuclear spin hyperpolarization. To this end, we demonstrate the utility of this parahydrogen generator for hyperpolarization of concentrated sodium [1-(13)C]pyruvate, a metabolic contrast agent under investigation in numerous clinical trials. The reported pilot optimization of SABRE-SHEATH (signal amplification by reversible exchange-shield enables alignment transfer to heteronuclei) hyperpolarization yielded (13)C signal enhancement of over 14,000-fold at a clinically relevant magnetic field of 1 T corresponding to approximately 1.2% (13)C polarization-if near 100% parahydrogen would have been employed, the reported value would be tripled to (13)C polarization of 3.5%. Imaging markers from MRI using D2O: Purpose: Water is a substrate in many biochemical pathways. Systemic administration of deuterated water (D2O) results in deuterium incorporation into nucleic acids, carbohydrates, proteins, and lipids. Given their relatively high rates of proliferation and resultant deuterium enrichment we hypothesized that tumors would be more easily discerned from healthy tissues via deuterium MRI. Methods: We initiated D2O administration in two xenograft mouse models harboring either human colorectal, HT-29, or pancreatic, MiaPaca2, cancers. Results: After 14 days of in vivo tumor growth and 7 days of systemic labeling with D2O, a clear dMRI contrast was demonstrated between the xenografts and normal tissue. Conclusions: Our novel clinically relevant labeling-imaging approach enables non-radioactive sensitive tumor detection and supports the use of deuterium in cancer imaging.