钆-纳米金双模态分子成像探针及其成像相互影响机制的研究

Multimodal imaging probe has been becoming an increasing hot topic in molecular imaging, however, there is still lack of sensitive and real-time methods to investigate the interaction mechanism among multimodality molecular imaging in vivo. Here, we will synthesize and characterize a novel magneto-optical dual-modal nanoprobe of the Gadolinium-doped mesoporous silica nanocomposites (Gd2O3@MCM-41) carrying gold nanoparticles (Gadolinium-Gold nanoprobe). Our pilot study results suggested that gold nanoparticles improve the effectiveness of contrast-enhanced magnetic resanonce imaging of Gd2O3@MCM-41 (R1 value of dual-modal nanoprobe is 1.66 times higher than that of Gd2O3@MCM-41), which syneristically influence the optic characteristics of gold nanoparticles, more sensitive to detect the real-time activities of molecules in vivo. Based on these innovative discoveries, we will investigate deeply the interactive mechanism between magneto-optical molecular imaging in vivo by a variety of techniques including magnetic resonance imaging, nuclear magnetic relaxation dispersion, simulated microstructures and composition analysis, fluorescence lifetime imaging, laser raman scattering spectrum, two-photon laser scanning fluorescence microscopy, inductively coupled plasma mass spectrometry and so on. In addition, we will systematically evaluate the safety and efficiency of this dual-modal probe including its biocompatibility in vitro (cytotoxicity, cell cycle and apoptosis in vitro) and in vivo (immunotoxicity), and its pharmacokinetics (blood circulation half-life, biodistribution and excretion) and pharmacodynamics (MR images of blood circulation and mice transplanted tumor tissue). Furthermore, this dual-modal probe will be specifically binded with antibodies or polypeptide (such as, integrin αvβ3-binding cyclic RGD peptide) for targeted imaging of maglinant tumor, so that we could real-time trace the activity and ligand-receptor interaction of integrin αvβ3 in vivo. The above researches could possibly provide a new targeted multimodal imaging probe and techniques for real-time molecular imaging and targeted diagnosis of early stage malignant tumor.

多模态分子成像与探针研制已成为分子影像学研究热点，但活体内各模态成像相互影响机制研究尚缺乏敏感、实时检测手段。本项目拟在成功研制钆-介孔硅肿瘤靶向性造影剂的基础上，通过纳米修饰，挂接具有光学成像和热趋向特性的纳米金颗粒，研制一种新型光磁双模态分子成像探针。前期研究发现，纳米金可增强钆纳米磁共振成像效果(R1值为钆纳米的1.66倍)；而磁性对纳米金光学特性有一定影响，更有利于检测靶分子在体活动动态过程。在此基础上，利用核磁弛豫分散技术，辅以微结构与成分模拟分析技术，探讨光学探针对磁性探针弛豫率的影响机制；利用超快荧光寿命成像、激光拉曼谱分析技术，辅以共聚焦荧光显微镜，观察磁性对光学探针荧光超快特性和空间分布的影响过程；实时观测该分子探针在活体内降解代谢过程，深入探讨光磁双模态分子成像相互影响机理。预进一步标记肿瘤靶分子，为活体内分子实时显像及恶性肿瘤早期诊断提供新的分子成像技术与靶向诊断探针

1. 在含钆介孔硅纳米造影剂研发基础上，通过纳米修饰，外挂接具有光学成像和热趋向特性的金纳米颗粒，研制一种高效能的光磁双模态成像探针，研究发现金纳米显著提高钆纳米的R1弛豫率（1.66倍）和肿瘤靶向显像的效率；而磁性对纳米金光学特性有一定影响，更有利于检测靶分子在体活动动态过程；初步分析金增强钆纳米磁性的机制，即掺入的金导致钆电子能量的增加，从而影响钆的磁性和氢质子的磁共振状态。同时，系统研究该探针的物理表征、光学成像与荧光寿命光谱、磁共振成像、生物毒性、药代动力学和药效学等生物影像的特性，为活体内实时分子显像及恶性肿瘤早期诊断提供新的分子成像技术与诊断探针。.2. 研发一种前蛋白转化酶Furin靶向的智能(Smart)磁共振造影剂：研制含缩合反应官能团的小分子钆化合物，在肿瘤细胞高表达Furin作用下，发生缩合反应生成两亲性多聚体，自组装成磁性纳米粒子，产生显著高于小分子单体的MR信号，实现肿瘤主动靶向显像。.3. 新型液相激光溶蚀纳米制备技术(Laser ablation in liquid,LAL) 制备的含钆纳米造影剂，具有制备工艺简单、磁共振成像效果好等优点；在此基础上，我们改进及优化LAL技术及制备工艺，通过结合固相烧结法与LAL技术，将发光稀土金属（Tm、Tb、Eu等）直接掺杂至Gd2O3纳米内，成功地制备出氧化钆掺杂发光稀土金属的三种结构稳定、超纯的光磁多模态成像探针：Gd2O3:Tm3+、Gd2O3:Tb3+、Gd2O3:Eu3+，并检测到了良好的荧光效果和磁共振成像效果。.上述重要成果极大地推动了磁共振分子影像学的发展，为活体内分子实时显像及恶性肿瘤早期诊断提供新的分子成像技术与靶向诊断探针。