液相激光溶蚀技术制备新型光磁双模态成像探针应用于肿瘤靶向显像研究

The development of a novel multimodal imaging probe has been becoming one of most important tasks for molecular imaging. We had previously reported on the synthesis and characterization of a multifunctional magneto-optical dual-modal nanoprobe based on the Gadolinium-doped mesoporous silica nanocomposites (Gd2O3@MCM-41) external carrying gold nanoparticles (Gadolinium-Gold nanoprobe),suggesting that gold nanoparticles significantly increase R1 value of dual-modal nanoprobe (1.66 times higher than that of Gd2O3@MCM-41) and improve the effectiveness of tumor-targeted imaging in vivo. However, the department of Gold from Gadolinium nanoparticles during in vivo severely halted the effectiveness of tumor-targeted imaging. A newly developed, simple and green technique for nanocomposites preparation -Laser ablation in liquid (LAL) has been proven to be a unique and efficient technique for generating nanoparticles. It does not necessarily require chemicals and does not necessarily produce waste. Specifically in our preliminary researches, we synthesized ligand-free monoclinic Mn3O4 and Gd2O3 nanocrystals using a microsecond laser, ablating a Mn/Gd target in deionized water. The R1 relaxivity of Mn3O4 NPs is 8.26 mM-1s-1, which is twice higher than that of the commercial Gd-DTPA contrast agent (4.11 mM-1s-1) and the highest value reported to date for Mn-based NPs. Based on the encouraging experimental results, we next optimize the preparation and propose a facile and environmentally friendly top-down technique to synthesize the rare earth doped-Gd2O3 nanocrystals at ambient environment. Using this approach, we synthesize a series of Tm3+, Tb3+, and Eu3+ doped-Gd2O3 nanoparticles colloids and observe strong blue, green, and red visible fluorescence from the as-synthesized nanoparticles colloids. In vitro and in vivo MRI show that these nanoparticles are good T1-weighted magnetic resonance imaging (MRI) contrast agents. The above results indicate that the synthesized rare earth doped-Gd2O3 nanocrystals could be used as MRI and fluorescence imaging dualmodal contrast agents. A variety of techniques including magnetic resonance imaging, nuclear magnetic relaxation dispersion, fluorescence lifetime imaging, laser Raman scattering spectrum will be used to investigate the interaction mechanism among multimodality molecular imaging in vivo. Furthermore, a self-developed ligand against Furin (a high-expressed subtilisin- like proprotein convertase in maglinant tumor) is specifically binded to the as-synthesized dual-modal probe for tumor-targeted imaging and real-time trace the activity and ligand-receptor interaction of Furin in vivo, in order to provide a novel targeted multimodal imaging probe for targeted diagnosis of early stage malignant tumor.

多模态分子成像探针研制是目前分子影像学研究热点.我们以前报道在含钆硅纳米造影剂上,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多模态成像探针,发现金纳米显著提高钆纳米的R1值以及肿瘤靶向显像的效率;但在活体内出现外挂接的金胶粒与钆纳米分离,致使靶向显像脱靶问题.前期研究采用新型液相激光溶蚀纳米制备技术(Laser ablation in liquid,LAL)研制含钆/锰纳米造影剂,具有制备工艺简单、磁共振成像效果好等优点;在此基础上,我们拟改进LAL制备技术,研制新型结构稳定的含钆/发光稀土金属(Eu、Tm、Tb等)光磁双模态成像探针,利用核磁弛豫分散技术、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),深入探讨光磁双模态成像相互影响机理.预进一步标记肿瘤靶分子Furin配体,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.

根据课题研究计划及研究目标，优化液相激光溶蚀纳米制备技术（Laser ablation in liquid, LAL）研制一系列新型含钆/发光稀土金属（Eu、Tm、Tb等）光磁双模态分子成像探针，应用于肿瘤的靶向显像研究，研究该双模态纳米探针的生物影像特性，及各模态分子成像的相互影响机制；实时观测该配体的在体活动的动态过程，提高新型探针在肿瘤组织靶向聚集效率。.在此基础上，进一步优化LAL纳米制备技术，通过双稀土金属（Yb/Er、Yb/Tm、Yb/Ho等）与钆掺杂，研制一类兼具磁共振成像和上转换发光性能的新型光磁纳米探针；该探针对组织光损伤小、穿透能力大的近红外具有很强的吸收作用，并发出可见波段的荧光，通过与传统的光敏剂结合，利用近红外光激发原位地对肿瘤部位实现光动力疗，初步探讨恶性肿瘤肿瘤的靶向诊断和光动力治疗一体化。

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