Tansi Felista L, Rüger Ronny, Rabenhold Markus, Steiniger Frank, Fahr Alfred, Hilger Ingrid
Experimental Radiology, Institute of Diagnostic and Interventional Radiology I, Jena University Hospital;
Department of Pharmaceutical Technology, Friedrich-Schiller-University Jena;
J Vis Exp. 2015 Jan 5(95):e52136. doi: 10.3791/52136.
Optical imaging offers a wide range of diagnostic modalities and has attracted a lot of interest as a tool for biomedical imaging. Despite the enormous number of imaging techniques currently available and the progress in instrumentation, there is still a need for highly sensitive probes that are suitable for in vivo imaging. One typical problem of available preclinical fluorescent probes is their rapid clearance in vivo, which reduces their imaging sensitivity. To circumvent rapid clearance, increase number of dye molecules at the target site, and thereby reduce background autofluorescence, encapsulation of the near-infrared fluorescent dye, DY-676-COOH in liposomes and verification of its potential for in vivo imaging of inflammation was done. DY-676 is known for its ability to self-quench at high concentrations. We first determined the concentration suitable for self-quenching, and then encapsulated this quenching concentration into the aqueous interior of PEGylated liposomes. To substantiate the quenching and activation potential of the liposomes we use a harsh freezing method which leads to damage of liposomal membranes without affecting the encapsulated dye. The liposomes characterized by a high level of fluorescence quenching were termed Lip-Q. We show by experiments with different cell lines that uptake of Lip-Q is predominantly by phagocytosis which in turn enabled the characterization of its potential as a tool for in vivo imaging of inflammation in mice models. Furthermore, we use a zymosan-induced edema model in mice to substantiate the potential of Lip-Q in optical imaging of inflammation in vivo. Considering possible uptake due to inflammation-induced enhanced permeability and retention (EPR) effect, an always-on liposome formulation with low, non-quenched concentration of DY-676-COOH (termed Lip-dQ) and the free DY-676-COOH were compared with Lip-Q in animal trials.
光学成像提供了广泛的诊断方式，作为生物医学成像工具已引起了广泛关注。尽管目前有大量的成像技术以及仪器设备取得了进展，但仍需要适用于体内成像的高灵敏度探针。现有临床前荧光探针的一个典型问题是它们在体内的快速清除，这降低了它们的成像灵敏度。为了规避快速清除，增加靶位点的染料分子数量，从而减少背景自发荧光，我们将近红外荧光染料DY-676-COOH包裹在脂质体中，并验证了其在体内炎症成像的潜力。DY-676以其在高浓度下能够自我猝灭而闻名。我们首先确定了适合自我猝灭的浓度，然后将该猝灭浓度包裹在聚乙二醇化脂质体的水相内部。为了证实脂质体的猝灭和激活潜力，我们使用了一种苛刻的冷冻方法，该方法会导致脂质体膜受损而不影响包裹的染料。具有高水平荧光猝灭特征的脂质体被称为Lip-Q。我们通过对不同细胞系的实验表明，Lip-Q的摄取主要通过吞噬作用，这反过来又能够表征其作为小鼠模型体内炎症成像工具的潜力。此外，我们使用小鼠的酵母聚糖诱导水肿模型来证实Lip-Q在体内炎症光学成像中的潜力。考虑到炎症诱导的增强渗透和滞留（EPR）效应可能导致的摄取，在动物试验中，将具有低浓度、未猝灭的DY-676-COOH的常开脂质体制剂（称为Lip-dQ）和游离的DY-676-COOH与Lip-Q进行了比较。
