Integrin is often significantly up-regulated in activated endothelial cells during tumor angiogenesis.The arginine-glycine-aspartic acid(RGD)peptide sequence is a specific recognition motif toανβ3 integrin.In this study,a RGD labeled,Poly lactic acid(PLA) coated ultrasmall paramagnetic iron oxide(USPIO)(referred to as RGD-PLA-USPIO)were developed and the ability to detect tumor angiogenesis was investigated in vitro and in vivo.Increased uptake of RGD-PLA-USPIO by human umbilical vein endothelial cells(HUVECs)was detected by Prussian blue stain and transmission electronic microscopy(TEM).Pronounced signal decrease in T2*-weighted magnetic resonance image(MRI)and heterogeneous arrangement of neovasculature of tumor tissue were clearly identified in Vx-2 tumor model.The MR signal of contralateral muscle only could be seen a slight background change after either RGD-PLA-USPIO or PLA-USPIO injection.These studies demonstrate the efficiency of RGD-PLA-USPIO to visualizeανβ3 integrin in activated tumor endothelial cells and its potential for detecting and monitoring tumor vasculature change after therapy.
目的:研究超顺磁性氧化铁(superparamagnetic iron oxide,SPIO)对周围质子的弛豫时间的影响,探讨不同颗粒、浓度SPIO的MR信号特征。方法:对不同粒径及浓度的SPIO颗粒进行磁共振扫描,记录各个粒径和浓度的SPIO颗粒的MR T1、T2、T2*值,评价其信号特征。结果:①不同粒径的SPIO颗粒T1值与浓度呈负相关线性关系;②当SPIO浓度较低时,随粒径减小T2和T2*值则上升明显;当SPIO浓度较高时,随粒径减小上升渐趋缓慢;③lg(T2)与SPIO颗粒粒径和浓度之间存在线性依存关系。结论:SPIO颗粒对MR信号的影响以T1和T2效应为主;T2值可作为SPIO颗粒MR成像的主要检测指标;SPIO粒径大小、浓度和T2值三者之间存在着特定的线性关系。
