荧光-钆双模态MR靶向对比剂对微小肿瘤VEGFR-2受体精准定位显像的实验研究

Precision Medicine is a new direction of molecular imaging because it combines both the optical and structural multimode fusion imaging that can significantly improve the imaging quality. Our previous study established that VEGFR-2 receptor of tumor cells and growing vessels is a prospective molecular target. Fluorescence-MR double mode targeted imaging on VEGFR-2 has a great potential for precise positioning and quantitative diagnosis of tumor. This study aims to construct a new MR targeting agent by combining the fluorescent VEGF127-133 and gadolinium (Gd) with the polylysine dendrimer surface. The particle size of the new agent is designed only about the 1/80 (5nm) of that used in our previous antibody study. Through a series of experiments, including an in-vitro cell experiment, in vivo fluorescence imaging, MR imaging, and pathology and toxicology experiments on knockout models, the tumor precise positioning and quantitative ability, absorption, distribution and metabolism, and as well as acute toxicity of the agent will be analyzed at the molecular, cellular, and tissue and organ levels. The imaging mechanism by which the new MR tumor targeting agent is designed will also be studied. This study is expected to generate new breakthroughs in three aspects of tumor targeting, agent carrier and MR targeting agent.

精准医学是分子影像学的发展方向，光学与结构多模融合成像能提高成像质量。经我们前期系列研究发现，肿瘤新生血管及肿瘤细胞膜上的VEGFR-2受体是一种理想的分子靶点，对其进行荧光-MR双模态靶向成像，有望实现肿瘤的精准定位和定量诊断。 本研究将荧光VEGF拮抗小肽(VEGF127-133)与钆（Gd）连接到聚赖氨酸树枝大分子表面，构建一种新型MR靶向对比剂，其粒径只有我们前期抗体实验的1/80(5nm)。通过体外细胞学实验、荷瘤动物活体内荧光成像、MR成像、病理及毒理学实验观察；从分子、细胞、组织和器官水平分析该对比剂肿瘤精准定位和定量的性能、吸收、组织分布、代谢规律及急性毒性情况，探讨其成像机制，为新型肿瘤MR靶向对比剂设计奠定实验基础。本研究在肿瘤靶点、对比剂的运载体和显像剂三个方面都实现了在前期实验基础上的新突破。

荧光 VEGF 拮抗小肽(VEGF127-133) 标记钆（Gd），构建靶向MR阳性对比剂VEGF127-133–Gd，并同时观察其体内外靶向显像能力。先行体外实验后，导入荷瘤动物模型体内，通过动物荧光成像系统观察本探针在体内分布与消除过程；进一步经MR扫描探讨其体内外肿瘤成像特性。细胞荧光实验表明CY5.5- VEGF125-136 （VEGF127-133为其核心区）实验组BEL-7402细胞膜膜及细胞核细胞膜融合图像可见大量靶向红色荧光物质 CY5.5- VEGF127-133；CY5.5-QK对照组未见明显红色荧光标记。体内荧光实验表明实验组尾静脉给药CY5.5- VEGF125-136，荧光信号迅速上升，5分钟达第一峰值后开始下降，60分钟信号再次上升，2小时信号达最大值，为第二靶向峰值，然后再次下降，4小时接近平扫。对照组尾静脉给药CY5.5-QK，荧光信号迅速上升，5分钟达峰值，后迅速下降，未见信号再次上升。体外细胞MRI靶向实验表明VEGF125-136-Gd实验组强化明显高于对照组QK-Gd，且随加入靶向钆剂增多强化增强，对照组QK-Gd未见明显强化。体内MRI靶向实验表明实验组尾静脉给药 VEGF125-136-Gd-Gd (0.2 mmol Gd/kg)，T1信号迅速上升，5分钟达第一峰值后开始下降，60分钟信号再次上升，2小时信号大最大值，然后再次下降，4小时接近平扫。对照组尾静脉给药QK-Gd，T1信号迅速上升，5分钟达峰值，后迅速下降，未见信号再次上升。初步结论; 体内外荧光实验表明CY5.5-VEGF125-136可以BEL-7402细胞膜VEGFR2受体为靶点靶向荧光成像。体内外MRI实验表明VEGF125-136-Gd可以BEL-7402细胞膜VEGFR2受体为靶点靶向MRI成像。