Samuelson Lynn E, Anderson Bernard M, Bai Mingfeng, Dukes Madeline J, Hunt Colette R, Casey Jonathon D, Han Zeqiu, Papadopoulos Vassilios, Bornhop Darryl J
Department of Chemistry, The Vanderbilt Institute for Chemical Biology and Vanderbilt-Ingram Cancer Center, Vanderbilt University, VU Station B 351822 Nashville, Tennessee 37235-1822, USA.
Department of Biochemistry &Molecular and Ceilular Biology, Georgetown University Medical Center, BSB Room 315, 3900 Reservoir Road NW, Washington, DC 20057, USA.
RSC Adv. 2014;4(18):9003-9011. doi: 10.1039/c3ra47161f. Epub 2014 Jan 3.
Advances in probes for cellular imaging have driven discoveries in biology and medicine. Primarily, antibodies and small molecules have been made for contrast enhancement of specific proteins. The development of new dendrimer-based tools offers opportunities to tune cellular internalization and targeting, image multiple modalities in the same molecule and explore therapeutics. The translocator protein (TSPO) offers an ideal target to develop dendrimer tools because it is well characterized and implicated in a number of disease states. The TSPO-targeted dendrimers reported here, primarily ClPhIQ-PAMAM-Gd-Liss, are cell membrane permeable nanoparticles that enable labeling of TSPO and provide contrast in fluorescence, electron microscopy and magnetic resonance imaging. The molecular binding affinity for TSPO was found to be 0.51 μM, 3 times greater than the monomeric agents previously demonstrated in our laboratory. The relaxivity per Gd of the ClPhIQ-PAMAM-Gd dendrimer was 7.7 and 8.0 mM s for and respectively, approximately double that of the clinically used monomeric Gd chelates. studies confirmed molecular selectively for labeling TSPO in the mitochondria of C6 rat glioma and MDA-MB-231 cell lines. Fluorescence co-registration with Mitotracker Green® and increased contrast of osmium-staining in electron microscopy confirmed mitochondrial labeling of these TSPO-targeted agents. Taken collectively these experiments demonstrate the versatility of conjugation of our PAMAM dendrimeric chemistry to allow multi-modality agents to be prepared. These agents target organelles and use complementary imaging modalities , potentially allowing disease mechanism studies with high sensitivity and high resolution techniques.
细胞成像探针的进展推动了生物学和医学领域的发现。主要来说，已制备了抗体和小分子用于增强特定蛋白质的对比度。新型树枝状大分子工具的开发为调节细胞内化和靶向、在同一分子中实现多种成像模式以及探索治疗方法提供了机会。转运蛋白（TSPO）是开发树枝状大分子工具的理想靶点，因为它具有明确的特征且与多种疾病状态相关。本文报道的靶向TSPO的树枝状大分子，主要是ClPhIQ - PAMAM - Gd - Liss，是细胞膜可渗透的纳米颗粒，能够标记TSPO并在荧光、电子显微镜和磁共振成像中提供对比度。发现其对TSPO的分子结合亲和力为0.51μM，比我们实验室之前证明的单体试剂高3倍。ClPhIQ - PAMAM - Gd树枝状大分子每钆的弛豫率分别为7.7和8.0 mM s，约为临床使用的单体钆螯合物的两倍。研究证实了在C6大鼠胶质瘤和MDA - MB - 231细胞系的线粒体中标记TSPO的分子选择性。与Mitotracker Green®的荧光共定位以及电子显微镜中锇染色对比度的增加证实了这些靶向TSPO的试剂的线粒体标记。总体而言，这些实验证明了我们的PAMAM树枝状大分子化学共轭的多功能性，能够制备多模态试剂。这些试剂靶向细胞器并使用互补的成像模式，有可能通过高灵敏度和高分辨率技术进行疾病机制研究。
