磁性纳米颗粒在小鼠巨噬细胞体外MRI中的应用

Objective To explore the optimal concentration for labeling mouse macrophage cell line RAW264.7 with ultra - micro superparamagnetic iron oxide nanoparticles (USPIO) and to compare the sensitivity differences of different scanning sequences in MRI for evaluating cell phagocytic function. Materials and Methods After co - culturing mouse macrophages with USPIO at final concentrations of 0, 25, 50, 75, 100, and 125 μg/mL for 24 h respectively, the cell counting kit - 8 (CCK - 8) was used to calculate the cell survival rate and the half - maximal inhibitory concentration (IC_(50)) of USPIO on the cells; the morphological changes of the cells were observed under an optical microscope; the phagocytic effect of the cells on USPIO was confirmed by Prussian blue staining; a 3.0 T MRI was used to scan the cell - agarose gel model, and the relaxation times and relaxation rates of T1WI and T2WI sequences were recorded and the relaxation time reduction rates were calculated. Results When the USPIO concentration was 25 μg/mL, there was no effect on the cell survival rate, and the difference was not statistically significant (P>0.05); when the USPIO concentration ≥50 μg/mL, the cell survival rate decreased significantly with the increase in USPIO concentration (all P<0.05); the half - maximal inhibitory concentration IC_(50) of USPIO on the cells was (186.5±7.2) μg/mL; when the USPIO concentration was 50 μg/mL, the cell morphology began to shrink and the light transmittance decreased; when the USPIO concentration was 25 μg/mL, the Prussian blue staining was significantly positive; MRI showed that compared with the control group, when the USPIO concentration was 25 μg/mL, significant signal changes were observed in the cells; with the increase in USPIO concentration, the T1 and T2 relaxation times were significantly shortened (all P<0.01), and the corresponding relaxation rates R1 and R2 gradually increased; at the same USPIO concentration, the reduction rate of T2 relaxation time in each group was significantly higher than that of T1 relaxation time (all P<0.001). Conclusions The USPIO at a concentration of 25 μg/mL has no obvious toxic effect on the cells, and has a high labeling efficiency and significant signal changes and good imaging effects in MRI, which is the optimal concentration for labeling macrophages; MRI can be used for in vitro imaging after cell labeling, and the T2WI sequence is superior to the T1WI sequence in detecting signal changes after cells phagocytize USPIO.

目的探讨应用超微超顺磁性氧化铁纳米颗粒(ultra-micro superparamagnetic iron oxide nanoparticle,USPIO)标记小鼠巨噬细胞株RAW264.7的最适浓度以及比较MRI中不同扫描序列在细胞吞噬功能评价中的敏感度差别。材料与方法用终浓度为0、25、50、75、100、125 μg/mL的USPIO分别与小鼠巨噬细胞共培养24 h后,细胞计数试剂法(CCK-8)计算细胞存活率以及USPIO对该细胞的半数抑制浓度(IC_(50));光学显微镜下观察细胞形态学变化;普鲁士蓝染色确认细胞对USPIO的吞噬效应;3.0 T MRI扫描细胞-琼脂糖凝胶模型,记录T1WI和T2WI序列的弛豫时间和弛豫率并计算弛豫时间降低率。结果当USPIO浓度为25 μg/mL时,对细胞的存活率无影响,差异无统计学意义(P>0.05);当USPIO浓度≥50 μg/mL时,细胞存活率随USPIO浓度增加显著降低(P均&0.05);USPIO对细胞的半数抑制浓度IC_(50)为(186.5±7.2) μg/mL;当USPIO浓度为50 μg/mL时,细胞形态开始皱缩、透光度减低;当USPIO浓度为25 μg/mL时,普鲁士蓝染色呈显著阳性;MRI显示,与对照组相比,当USPIO浓度为25 μg/mL时,细胞即见显著信号改变;随USPIO浓度增加,T1、T2弛豫时间显著缩短(P均&0.01),对应弛豫率R1、R2逐渐升高;相同USPIO浓度下,各组T2弛豫时间降低率显著高于T1弛豫时间降低率(P均&0.001)。结论浓度为25 μg/mL的USPIO对细胞没有明显毒性作用,而且标记效率高、MRI即见显著信号改变与较好的成像效果,为标记巨噬细胞的最适浓度;MRI能用于细胞标记后的体外成像,T2WI序列在检测细胞吞噬USPIO后的信号变化优于T1WI序列。