超敏明胶酶靶向超小超顺氧化铁纳米粒子的合成及其检测胃癌的实验研究

MMP2/MMP9 Targeted Polymeric Micelle Loading with USPIO as a Novel MRI Ultrasensitive Agent for Detection of Gastric Cancer

目的合成明胶酶靶向的超小超顺氧化铁纳米粒子,探讨其作为磁共振成像(MRI)特异性显影剂用于检测胃癌的效果。方法两性共聚物聚乙二醇(PEG)-聚己内酯(PCL)中间被插入了1个6个氨基酸肽段(PVGLIG),该肽段可以被肿瘤组织局部高浓度的明胶酶Ⅳ(MMP2/MMP9)所降解。该共聚物(PEG-Pep-PCL)通过纳米沉淀法负载超小超顺氧化铁纳米粒子(USPIO),最后形成PEG-Pep-PCL-USPIOs。通过调节PCL的长度,使PEG-Pep-PCL-USPIOs粒子直径控制在95 nm左右,使其可以更好地利用肿瘤组织的渗透增强滞留效应(EPR)。结果体外摄取实验证明胃癌肿瘤细胞对PEG-Pep-PCL-USPIOs的摄取明显大于对照组的PEG-PCL-USPIOs和常规纳米氧化铁粒子Resovist(P<0.01)。体内试验中,相同铁剂量的PEG-Pep-PCL-USPIOs、PEG-PCL-USPIOs和Resovist通过尾静脉注射于皮下负载胃癌细胞株SGC-7901的裸鼠,经7.0T的小动物核磁检测,PEG-Pep-PCL-USPIOs的T2-WI信号衰减程度明显大于PEG-PCL-USPIOs组和Resovist组(P<0.01),肿瘤组织的病理切片检测亦证实上述结果。结论 PEG-Pep-PCL-USPIOs具有作为胃癌早期检测的MRI特异性显影剂的潜力。

Objective To explore the role of MMP2 /MMP9 targeted polymeric micelle loading with ultrasmall superparamagnetic iron oxide nanoparticle（ USPIO） synthesized as a novel MRI ultrasensitive agent for the detection of gastric cancer. Methods The copolymer of poly5k（ ethylene glycol,PEG） and poly6. 5k（ ε-caprolactone,PCL） was inserted a peptide of six amino acids（ PVGLIG） which could be degraded by MMP2 / MMP9（ gelatinase）,whereas the gelatinase was secreted by major gastric tumor. The copolymer was loaded with USPIO by using nanoparticle precipitation to obtain PEG-Pep-PCL-USPIOs. The length of PCL segment was shortened to keep the final diameter of PEG-Pep-PCL micelles at 95 nm approximately,which was beneficial to utilize the EPR effect in maximum. Results The test in vitro identified that the amount of PEG-Pep-PCL-USPIOs which was absorbed by tumor cells was much more than that of PEG-PCL-USPIOs or Resovist in the control group（ P〈0. 01）. In vivo study,PEG-Pep-PCL-USPIOs,PEG-PCL-USPIOs,Resovist solutions,with the same addition of ferrovanadium,were injected into nude mice bearing subcutaneous xenografts of human SGC-7901 gastric carcinoma,respectively,and imaged by 7. 0T MRI. The signal decrease in T2-weighted images within tumor location in PEG-Pep-PCL-USPIOs group was much more than that in PEG-PCL-USPIOs group or Resovist group（ P〈0. 01）. The prussian blue staining of the tumor sections excised also proved the results above. Conclusion PEG-Pep-PCL-USPIOs can act as a promising MRI ultrasensitive agent for the early detection of gastric cancer.