钆-纳米金双模态分子成像探针的研制

Synthesis and characterization of dual-modal molecular imaging nanoprobes with gadolinium and gold nanoparticles

目的 制备一种钆-纳米金复合物作为光和磁双模态分子成像探针,评估其分子影像学应用的可行性.方法 在成功研制的钆-介孔硅磁共振对比剂的基础上,利用聚乙烯亚胺（PEI）进行表面改性,进而挂接带负电荷的30 nm的金颗粒,制备钆-纳米金复合物.透射电镜观察其物理表面特性,X射线能谱仪测量钆、金等各元素所占比例,紫外吸收光谱仪测定其吸收光谱,皮秒条纹相机测定其时间分辨荧光光谱,利用核磁弛豫分散技术分析其纵向弛豫率R1,MTT法测定其细胞毒性,共聚焦荧光显微镜分析其在骨髓间充质干细胞的光学成像效果,透射电镜分析其在组织内的亚细胞分布,3.0 T核磁共振扫描仪观察其在脾脏肝转移瘤小鼠中的成像效果.结果 30 nm的金颗粒成功挂接在PEI包裹的钆-介孔硅分子探针上.X射线能谱仪分析其Gd和Au元素所占比例为6.74％和0.52％.紫外吸收光谱分析其在525 nm处和近红外749 nm处均有吸收峰.时间分辨荧光光谱表明其发光有一个宽的发光带（525～560 nm）,发光峰位于550 nm.其纵向弛豫率R1为3.171 nmol-1＆#183;L＆#183;s-1.MTT法显示其细胞毒性甚微.裸鼠尾静脉注射4h后,透射电镜显示其组织内的纳米金颗粒被降解分离.其具有很好的细胞共聚焦荧光成像效果.裸鼠尾静脉注射30 min,肿瘤的磁共振图像明显强化.结论 成功制备了光和磁双模态分子成像探针,为肿瘤的早期诊断提供了依据.

Objective To prepare a dual-modal nanoprobes with gadolinium and gold nanoparticles for optical and magnetic resonance imaging,and validate its efficiency in molecular imaging.Methods The gadolinium-gold nanocomposite particles were prepared by immobilizing negatively-charged 30 nm gold nanoparticles on polyethyleneimine （PEI）-treated surface of the gadolinium-mesoporous silica.For the prepared nanoparticles,we used transmission electron microscopy （TEM） to determine the surface physical properties,energy dispersive X-ray spectroscopy to determine the constitution ratios of gadolinium and gold,ultraviolet spectrometry to determine the absorption spectra,picosecond streak camera to determine the timeresolved fluorescence spectra,and nuclear magnetic relaxation dispersion to determine the longitudinal relaxivity （R1）.Cell toxicity was measured by MTT;Optical imaging in bone-marrow mesenchymal stem cells was evaluated by confocal fluorescence microscopy;Biodistribution was detected by TEM;Dynamic contrastenhanced T1-weighted magnetic resonance （MR） images of metastatic liver tumors in the spleen were analyzed using a 3.0 T MR scanner.Results Black gold particles （30 nm） were successfully immobilized on the surface of PEI-coated gadolinium-mesoporous silica spheres.The atomic percent of gadolinium and gold is 6.74% and 0.52%,respectively,according to energy dispersive X-ray spectroscopy.The ultraviolet absorption spectra revealed the absorption peaks at 525 nm and 749 nm.Time-resolved fluorescence spectra revealed a wide luminescence band （525～560 nm）,with a luminescence peak at 550 nm.The relaxivity R1 was 3.171 nmol-1＆#183; L ＆#183; s-1.The cytotoxicity is negligible as measured by MTL TEM indicated that the gold nanoparticles were separated from nanocomposites in the tissues at 4 h after injected into nude mice via tail vein.Optical imaging in cells are satisfactory.The significant enhancement of tumor MRI was demonstrated at 30 min after intravenous administration.Conclusion The optic-magnetic dual-modal molecular imaging nanoprobes were successfully prepared,and could provide a potential platform for the early diagnosis of cancer.