Biomedical NMR, Department of Biomedical Engineering, Eindhoven University of Technology, Eindhoven, The Netherlands.
J Control Release. 2012 Mar 10;158(2):207-14. doi: 10.1016/j.jconrel.2011.10.032. Epub 2011 Oct 30.
Molecular imaging of angiogenesis requires a highly specific and efficient contrast agent for targeting activated endothelium. We have previously demonstrated that paramagnetic and fluorescent liposomes functionalized with two angiogenesis-specific ligands, the galectin-1-specific anginex (Anx) and the α(v)β(3) integrin-specific RGD, produce synergistic targeting effect in vitro. In the current study, we applied Anx and RGD dual-conjugated liposomes (Anx/RGD-L) for angiogenesis-specific MRI in vivo, focusing on the specificity and efficacy of liposome association with tumor endothelium. The targeting properties, clearance kinetics and biodistribution of Anx/RGD-L were investigated in B16F10 melanoma-bearing mice, and compared to liposomes functionalized with either Anx (Anx-L) or RGD (RGD-L). The contrast enhancement produced by dual- and single-targeted nanoparticles in the tumor was measured using in vivo T(1)-weighted MRI, complemented by ex vivo immunohistochemical evaluation of tumor tissues. Blood clearance kinetics of Anx/RGD-L was three-fold more rapid than for RGD-L, but comparable to Anx-L. Both dual- and single-targeted liposomes produced similar changes in MRI contrast parameters in tumors with high inter-tumor variability (ΔR(1)=0.04±0.03s(-1), 24h post-contrast). Importantly, however, the specificity of Anx/RGD-L association with tumor endothelium of 53±6%, assessed by fluorescence microscopy, was significantly higher compared to 43±9% (P=0.043) and 28±8% (P=0.0001) of Anx-L and RGD-L, respectively. In contrast, long-circulating RGD-L were on average 16% more efficient in targeting tumor endothelium compared to Anx/RGD-L. Significant differences were also found in the biodistribution of investigated contrast agents. In conclusion, synergistic targeting of α(v)β(3) and galectin-1 improved the specificity of the association of the liposomal contrast agent to tumor endothelium in vivo, providing therefore a more reliable MRI readout of the angiogenic activity.
血管生成的分子成像需要一种高度特异和高效的对比剂来靶向激活的内皮细胞。我们之前已经证明，用两种血管生成特异性配体（半乳糖凝集素-1特异性的 Anginex（Anx）和α（v）β（3）整合素特异性的 RGD）功能化的顺磁和荧光脂质体，在体外产生协同靶向效应。在本研究中，我们将 Anginex 和 RGD 双重偶联脂质体（Anx/RGD-L）应用于体内血管生成特异性 MRI，重点研究脂质体与肿瘤内皮细胞结合的特异性和效力。在 B16F10 黑色素瘤荷瘤小鼠中研究了 Anx/RGD-L 的靶向特性、清除动力学和生物分布，并与 Anginex （Anx-L）或 RGD （RGD-L）功能化的脂质体进行了比较。通过体内 T1 加权 MRI 测量了双靶向和单靶向纳米粒子在肿瘤中产生的对比增强，并用肿瘤组织的离体免疫组织化学评估进行补充。Anx/RGD-L 的血液清除动力学比 RGD-L 快三倍，但与 Anginex-L 相当。双靶向和单靶向脂质体在肿瘤中产生的 MRI 对比参数变化相似，但肿瘤间变异性很大（ΔR1=0.04±0.03s-1，对比后 24 小时）。然而，重要的是，荧光显微镜评估的 Anginex/RGD-L 与肿瘤内皮细胞的结合特异性为 53±6%，明显高于 Anginex-L（43±9%，P=0.043）和 RGD-L（28±8%，P=0.0001）。相比之下，长循环的 RGD-L 平均比 Anx/RGD-L 更有效地靶向肿瘤内皮细胞 16%。研究对比剂的生物分布也存在显著差异。总之，α（v）β（3）和半乳糖凝集素-1 的协同靶向作用提高了脂质体对比剂与体内肿瘤内皮细胞结合的特异性，从而为血管生成活性提供了更可靠的 MRI 读出。
