Department of Biomedical Engineering, Case Western Reserve University, Cleveland, OH 44106, USA.
Theranostics. 2011 Jan 19;1:83-101. doi: 10.7150/thno/v01p0083.
Magnetic resonance imaging (MRI) is a powerful medical diagnostic imaging modality for integrin targeted imaging, which uses the magnetic resonance of tissue water protons to display tissue anatomic structures with high spatial resolution. Contrast agents are often used in MRI to highlight specific regions of the body and make them easier to visualize. There are four main classes of MRI contrast agents based on their different contrast mechanisms, including T(1), T(2), chemical exchange saturation transfer (CEST) agents, and heteronuclear contrast agents. Integrins are an important family of heterodimeric transmembrane glycoproteins that function as mediators of cell-cell and cell-extracellular matrix interactions. The overexpressed integrins can be used as the molecular targets for designing suitable integrin targeted contrast agents for MR molecular imaging. Integrin targeted contrast agent includes a targeting agent specific to a target integrin, a paramagnetic agent and a linker connecting the targeting agent with the paramagnetic agent. Proper selection of targeting agents is critical for targeted MRI contrast agents to effectively bind to integrins for in vivo imaging. An ideal integrin targeted MR contrast agent should be non-toxic, provide strong contrast enhancement at the target sites and can be completely excreted from the body after MR imaging. An overview of integrin targeted MR contrast agents based on small molecular and macromolecular Gd(III) complexes, lipid nanoparticles and superparamagnetic nanoparticles is provided for MR molecular imaging. By using proper delivery systems for loading sufficient Gd(III) chelates or superparamagnetic nanoparticles, effective molecular imaging of integrins with MRI has been demonstrated in animal models.
磁共振成像（MRI）是一种强大的医学诊断成像方式，用于整合素靶向成像，它利用组织水质子的磁共振来显示具有高空间分辨率的组织解剖结构。对比剂通常用于 MRI 中突出身体的特定区域，使其更容易可视化。根据不同的对比机制，MRI 对比剂主要有四类，包括 T(1)、T(2)、化学交换饱和转移（CEST）试剂和异核对比剂。整合素是异二聚体跨膜糖蛋白家族，作为细胞-细胞和细胞-细胞外基质相互作用的介质。过度表达的整合素可以作为设计合适的整合素靶向对比剂用于 MR 分子成像的分子靶点。整合素靶向对比剂包括针对靶整合素的靶向剂、顺磁剂和连接靶向剂与顺磁剂的接头。靶向剂的适当选择对于靶向 MRI 对比剂有效地与整合素结合以进行体内成像至关重要。理想的整合素靶向 MR 对比剂应该是无毒的，在靶位提供强烈的对比增强，并且在 MR 成像后可以完全从体内排出。本文概述了基于小分子和大分子 Gd(III)配合物、脂质纳米粒和超顺磁纳米粒的整合素靶向 MR 对比剂，用于 MR 分子成像。通过使用适当的递送系统来装载足够的 Gd(III)螯合物或超顺磁纳米粒，已经在动物模型中证明了使用 MRI 对整合素进行有效的分子成像。
