Developing MRI sensors for monitoring Zn2+ using iCEST

金属离子在无数的生物过程中起着至关重要的作用，并且能够实时监测 金属离子水平对于理解各种生理事件是必不可少的。虽然动态成像 金属离子水平的变化在体外使用基于光学的响应染料是适用的， 组织穿透，体内深层组织中游离金属离子的非侵入性检测仍然是一个艰巨的任务。 挑战.基于MRI的传感器允许对具有无限组织的同一受试者进行纵向研究 渗透，这可能是有用的研究动态生物过程，如发生和 疾病的进展和建议的治疗的功效。此外，重要的是，MRI传感器 具有临床转化的潜力。该提案旨在设计、合成、表征和优化 氟化螯合物用于Zn 2+成像，使用最近开发的称为离子化学交换的方法 饱和转移（iCEST）-MRI。我们最近表明，使用钙的氟化衍生物， 螯合物，5，52-二氟BAPTA（5 F-BAPTA），允许检测低的，生物相关浓度的 使用iCEST钙。作为第一步，将合成一系列用于Zn 2+成像的潜在iCEST传感器 并研究了其监测不稳定锌离子的能力。离解常数等性质 (Kd)，19 F-NMR谱中结合和游离螯合物之间的频率偏移（（汇率） (kex)、对Zn 2+的特异性（与竞争性离子相比）和对比度增强，这些都是对 iCEST代理的设计将受到审查。然后，优选探针的局限性，例如 将检查探针的可检测性水平和可检测Zn 2+浓度的动态范围。作为 作为一个潜在的应用实例，我们将利用我们研究小组的丰富经验， 胰岛细胞作为糖尿病的治疗策略。由于胰腺β细胞分泌的胰岛素 伴随着高浓度的锌被释放到细胞外空间，监测Zn 2+， 被认为是胰腺β细胞功能的生物标志物。我们将监测Zn 2+从治疗药物中的释放， 并将这些水平（通过iCEST检测）关联起来 方法学）与胰岛素分泌，即，他们的功能和治疗能力。在完成此 研究，我们预计建立一种新的方法，成像不稳定的锌2+在生物系统中使用MRI， 将适用于广泛的生物医学应用，并将推出一种新的成像策略， 生物相关的金属离子。

Metal ions play a crucial role in myriad biological processes, and the ability to monitor real-time changes in metal ion levels is essential for understanding a variety of physiological events. Although imaging of dynamic changes in metal ion levels is applicable in vitro using optical-based responsive dyes, which are limited by low tissue penetration, noninvasive detection of free metal ions in vivo in deep tissues remains a formidable challenge. MRI-based sensors allow the longitudinal study of the same subject with unlimited tissue penetration, which may be useful for studying dynamic biological processes, such as the occurrence and progression of diseases and the efficacy of suggested therapeutics. Moreover, and importantly, MRI sensors have the potential for clinical translation. This proposal aims to design, synthesize, characterize, and optimize fluorinated chelates for Zn2+ imaging using a recently developed approach called ion Chemical Exchange Saturation Transfer (iCEST)-MRI. We have recently shown that using a fluorinated derivative of a calcium chelate, 5,52-difluoro BAPTA (5F-BAPTA), allows the detection of low, biologically relevant concentrations of calcium using iCEST. As a first step, a series of potential iCEST sensors for Zn2+ imaging will be synthesized and studied to characterize their ability to monitor labile zinc ions. Properties such as the dissociation constant (Kd), the frequency offset between bound and free chelate in the 19F-NMR spectrum (¿), the exchange rate (kex), the specificity for Zn2+ (compared to competitive ions), and contrast enhancement, which are all critical for the design of iCEST agents, will be examined. Then, the limitations of the preferred probes, such as the detectability levels of the probe and the dynamic range of detectable Zn2+ concentrations, will be examined. As an example of a potential application, we will capitalize on the ample experience of our research group in pancreatic islet cells as a therapeutic strategy for diabetes. Since insulin secretion from pancreatic beta cells is accompanied by a high concentration of zinc that is released into the extracellular space, monitoring Zn2+ is considered a biomarker for pancreatic beta cell function. We will monitor the Zn2+ release from therapeutic pancreatic islet cells upon the addition of glucose and correlate these levels (detected by the iCEST methodology) with insulin secretion, i.e., their functionality and therapeutic capabilities. Upon completion of this study, we anticipate establishing a new approach to imaging labile Zn2+ in biological systems using MRI, which will be applicable to a broad spectrum of biomedical applications and will launch a novel strategy for imaging biologically relevant metal ions.