可激活核酸适配体磁共振成像分子探针在肿瘤细胞成像中的应用

Although various diagnostic and analytical detection methods for disease and disease-related biomarkers are currently available, developing molecular imaging techniques closely related to clinical applications is still in demand. Magnetic resonance molecular imaging is a type of technique utilizing MRI to image specific biomolecules in the body, which could achieve early prognosis of disease and monitoring of the therapeutic effect after treatment. The design and preparation of molecular imaging probe is the key to this technique. However, high background, low image contrast and limited sensitivity of the most studied targeting MRI molecular probe hampered wider applications of this technique. Activatable MRI molecular probe has great potential in future research. However, very limited applications of activatable MRI molecular probe have been reported so far and the scope of the targets is narrow. To our knowledge, no activatable MRI molecular probe has been developed for cellular or in vivo applications. Thus, more research should be conducted to better transfer this technique for clinical applications. In this project we plan to develop microwave-assisted polyol method to prepare PEG-Gd2O3 nanoparticles as contrast agent and propose that by designing smart activatable aptamer MRI molecular probes which integrate targeting and internalization ability of aptamer and magnetic resonance switching effect, MUC1 protein on MCF-7 cell surface and tumor-related C-myc mRNA in living cells can be detected as model targets. With the success of this project, MR molecular imaging applications for the detection of tumor cells can be realized.

在对疾病及疾病标志物甄定与检测的众多分析方法中，发展与临床应用密切相关的分子成像技术具有重要意义。磁共振分子成像利用磁共振成像（MRI）技术对体内特定分子进行成像，实现对病变早期、特异性诊断与疗效监测。其中，分子成像探针的设计与制备居于核心地位。研究较多的靶向性MRI分子探针存在的高本底背景、成像对比度不高以及灵敏度有限等问题使得可激活MRI分子探针逐渐成为未来的研究趋势。然而，目前该类探针的应用报道较少，研究对象范围相对狭小，并无涉及细胞和活体水平的MRI检测报道，在向临床应用转化过程中还需进行一系列深入研究。基于此，本项目拟发展微波多元醇法制备PEG-Gd2O3作为造影剂，分别以人乳腺癌细胞表面MUC1蛋白及活细胞内肿瘤相关C-myc mRNA为诊断对象，利用适配体的靶向识别与细胞内化能力、磁弛豫开关效应设计制备可激活核酸适配体MRI分子探针，实现肿瘤细胞磁共振分子成像检测应用。

疾病的早期诊断对于疾病的有效治疗起到关键作用。传统的影像学检查方法主要针对病变组织的结构形态异常，而分子影像学是基于影像学手段在分子或细胞水平反映生物体生理、病理变化，为疾病的早期诊断提供重要帮助。其中，高度特异性和亲和力分子探针的制备处于核心地位。本项目中，以聚乙二醇为溶剂和表面活性剂，制备具有较好磁共振成像对比增强能力的纳米对比剂PEG-Gd2O3，研究其在体生物学行为，并构建PEG-Gd2O3/aptamer-Ag NCs荧光/MR双模态分子成像探针以及谷胱甘肽响应的可激活磁共振分子成像探针Fe3O4-SS-PEG-Gd2O3用于肿瘤细胞的靶向成像。同时利用金属银纳米簇荧光性能受DNA模板和周围DNA环境变化而产生变化的特点，设计制备针对细胞内肿瘤相关mRNA的信号增强和光谱变化的可激活荧光分子成像纳米探针，为肿瘤的特异性灵敏检测提供实验基础。