Erdogan Suna, Torchilin Vladimir P
Department of Radiopharmacy, Faculty of Pharmacy, Hacettepe University, Ankara, Turkey.
Methods Mol Biol. 2010;605:321-34. doi: 10.1007/978-1-60327-360-2_22.
Magnetic resonance (MR) is one of the most widely used imaging modalities in contemporary medicine to obtain images of pathological areas. Still, there is a big effort to facilitate the accumulation of contrast in the required zone and further increase a local spatial concentration of a contrast agent for better imaging. Certain particulate carriers able to carry multiple contrast moieties can be used for an efficient delivery of contrast agents to areas of interest and enhancing a signal from these areas. Among those carriers, liposomes draw special attention because of their easily controlled properties and good pharmacological characteristics. To enhance the signal intensity from a given reporter metal in liposomes, one may attempt to increase the net quantity of carrier-associated reporter metal by using polylysine (PLL)-based polychelating amphiphilic polymers (PAP). In addition to heavy load of reporter metal onto the pharmaceutical nanocarrier (liposome), the accumulation of the contrast nanoparticles in organs and tissues of interest (such as tumors) can be significantly enhanced by targeting such particles both "passively," via the so-called enhanced permeability and retention (EPR) effect, or "actively," using various target-specific ligands, such as monoclonal antibodies. Combining three different properties--heavy load with Gd via the liposome membrane-incorporated PAP and tumor specificity mediated by the liposome-attached mAb 2C5--in a single nanoparticle of long-circulating (PEGylated) liposomes could provide a new contrast agent for highly specific and efficient tumor MRI.
磁共振成像（MR）是当代医学中应用最为广泛的成像方式之一，用于获取病变区域的图像。尽管如此，人们仍在努力促使造影剂在所需区域聚集，并进一步提高造影剂在局部的空间浓度，以实现更好的成像效果。某些能够携带多个造影基团的微粒载体可用于将造影剂有效递送至感兴趣的区域，并增强这些区域的信号。在这些载体中，脂质体因其易于调控的性质和良好的药理学特性而备受关注。为了增强脂质体中特定报告金属的信号强度，可以尝试通过使用基于聚赖氨酸（PLL）的多螯合两亲聚合物（PAP）来增加与载体相关的报告金属的净含量。除了将大量报告金属负载到药物纳米载体（脂质体）上之外，通过所谓的增强透过率和滞留（EPR）效应“被动”靶向，或使用各种靶向特异性配体（如单克隆抗体）“主动”靶向，可以显著增强造影纳米颗粒在感兴趣的器官和组织（如肿瘤）中的聚集。将三种不同的特性——通过掺入脂质体膜的PAP负载大量钆以及由附着在脂质体上的单克隆抗体2C5介导的肿瘤特异性——整合到单个长循环（聚乙二醇化）脂质体纳米颗粒中，可为高特异性和高效的肿瘤磁共振成像提供一种新型造影剂。
