基于NaGdF_4:Yb,Er纳米颗粒的磁共振/上转换发光双模态探针的构建及胰腺癌体内成像研究

Magnetic/upconversion fluorescent NaGdF_4:Yb,Er Nanoparticle-based dual-modal molecular probes for in-vivo imaging of pancreatic cancer

目的制备以顺磁性稀土纳米颗粒为基质的高发光强度上转换纳米颗粒,并对其表面生物相容性及功能化修饰,分析肿瘤靶向纳米探针在胰腺癌诊断的成像应用,为下一步术中导航奠定基础。方法采用高温法合成NaGdF_4:Yb,Er纳米颗粒,表面构建核壳结构,外修饰聚乙二烯(PEG)以增强发光强度及生物相容性,耦联靶向基团实现胰腺癌特异性组织识别。通过胰腺癌原位动物模型开展磁共振/上转换发光双模态成像及病理学评估。结果标准化Er^(3+)粒子浓度以后,包壳后纳米颗粒的整体发光强度是包壳前的70倍,平均粒径为(18.6±0.9)nm。耦联靶向基团后水合尺寸明显增大,但未出现其他峰位。靶向探针在体外实验中较对照组有明显T1信号增强作用。MRI成像结果,探针于肿瘤T1增强的峰值时间出现在注射后4 h,肿瘤区域T1信号下降达79%。上转换成像结果,上转换发光峰值时间也出现在第4小时,之后随时间持续下降。探针组织分布大部分集中在正常肺脏,但摄取量很低,不及注射总量的10%,表现出很好的安全性。结论基于上转换发光纳米颗粒探针,在体内能够实现胰腺癌的检测,展现出了在早期胰腺癌诊断及术中导航的临床转化价值。

Objective Molecular imaging probes based on upconversion nanoparticles with unique optical and magnetic properties are promising for early pancreatic cancer detection. Urokinase plasminogen activator receptor（uPAR）,a cellular receptor that is highly expressed in pancreatic cancer and tumor stromal cells, is an excellent surface molecule for receptor-targeted imaging.uPAR-targeted upconversion nanoparticles change the traditional single and down conversion luminescent imaging mode because near-infrared excitation can penetrate tissue better than visible light with greatly reduced background noise. Methods The uPARtargeted probe is designed and prepared by conjugating amino-terminal fragment of the receptor binding domain of human urokinase plasminogen activator to the surface of upconversion nanoparticles..The orthotopic human pancreatic cancer xenograft model was established by surgical implantation in nude mice..A stable luciferase-expressing SW1990 cell line, which is a typical pancreatic cancer cell line, was used to enable constant monitoring of tumor development. Ten days after surgical implantation, the nude mice were screened by bioluminescence imaging to verify successful inoculation..Only mice exhibiting comparable bioluminescence intensities were chosen for parallel studies. Results Targeted nanoparticles can specifically bind to uPAR-expressing tumor cells.The primary tumor and adjacent lymphatic metastasis site were clearly differentiated by upconversion luminescence imaging after the uPAR-specific probe was delivered through tail vein injection into tumor-bearing nude mice..Target specificity of nanoparticles was confirmed by 3T MRI..The mice injectedwith targeted nanoparticles exhibited lower uptake of the particles in the liver and spleen compared to those receiving non-targeted upconversion nanoparticles. Conclusion The uPAR-specific probe is useful for detecting tiny tumor lesion and lymphatic metastasis. It is promising for early pancreatic cancer diagnosis and lymph node evaluation.