摘要：
Objective To prepare a novel loaded NdFeB and Fe3O4 liquid-solid phase inversion poly (polylactic-co-glycolic acid,PLGA) in situ implant (PLGA 60％ NdFeB-20％ Fe3O4) for ultrasound-guided intratumoral injection,and to investigate its intensity of magnetism and therapeutic efficiency of nude mice bearing MDA-MB-231 breast cancer.Methods PLGA-60 ％ NdFeB-20 ％ Fe3O4 in situ implant was prepared.The microstructure of PLGA-60 ％ NdFeB-20 ％ Fe3O4 was tested with scanning electron microscope (SEM).Magnetometer was used to qualify the intensity of magnetism.For the in vitro assay,60 μl solid PLGA-60％ NdFeB-20％ Fe3O4 implant was put in the center of the electromagnetic induction heating coil.Infrared thermal video of the tubes was simultaneously recorded.The size of 2 cm × 2 cm× 2 cm fresh ex vivo bovine liver was prepared,and then 60 μl PLGA-60％ NdFeB-20％ Fe3O4 was injected into it.Similarly,ex vivo bovine liver was heated by the above intermittent time for 1,2,3,4 minutes,respectively,and the ablation volume was calculated.Finally,nude mice were equally divided into treatment group and control group.Mice in treatment group were discontinuously heated for 3 min after being injected with the above mentioned implant,while CEUS was performed before and after heating to observe the blood perfusion in the tumor.One nude mouse was executed on the next day in each group,then pathological sections and HE staining of tumor tissue were taken,whereas the growth of the remaining nude mice were observed daily.Results SEM showed the implant with rough and porous surface.The magnetism increased with the volume of material.The tube and bovine liver experiments showed that the PLGA-60 ％ NdFeB-20％ Fe3O4 generated heat efficiently.The bovine liver ablation experiment showed that the range of ablation of 60 μl PLGA-60 ％ NdFeB-20％ Fe3O4 implant reached (2.34±0.25)cm3 after 3 min heating.In vivo experiments showed that the tumor tissue began to form a scab on the 2nd day,and the scab began to desquamate on the 20th day.CEUS showed the original predominant enhancement disappeared significantly after the treatment.HE staining proved that cancer cells had coagulative necrosis,whereas tumors in control group became bigger.Conclusion PLGA-60％ NdFeB-20％ Fe3O4 in situ implant can produce obvious thermal effect under high frequency alternating magnetic field,therefore can be effectively ablated with nude mice MDA-MB-231 breast cancer during time interval heating.%目的 制备一种新型载钕铁硼(NdFeB)和Fe3O4液固相变型聚乳酸-羟基乙酸共聚物(PLGA)原位植入物(PLGA 60％NdFeB-20％Fe3O4),观察其在高频交变磁场下间隔加热的产热情况、磁性大小及对裸鼠MDA-MB-231乳腺癌的治疗效果.方法 制备PLGA-60％NdFeB-20％Fe3O4原位植入物,以扫描电镜观察其内部结构,磁力计测量磁性大小.取4块60μl PLGA-60％ NdFeB-20％ Fe3O4在离心管内间隔加热10 min,用红外仪观测温度变化;另取2 cm×2 cm×2 cm新鲜离体牛肝,向牛肝块内注射60μl PLGA-60％ NdFeB-20％ Fe3O4,置于线圈中分别加热1、2、3、4 min,之后立即剖开,计算消融体积.于超声引导下向裸鼠瘤内注射60μl PLGA-60％ NdFeB-20％ Fe3O4,将裸鼠分为治疗组和对照组:治疗组磁热治疗3 min,加热前后行CEUS,观察肿瘤内部血流灌注情况;对照组不做加热处理;次日两组分别处死1只裸鼠,取肿瘤组织行病理切片和HE染色,并每日观察剩余裸鼠的生长情况.结果 制备的PLGA-60％NdFeB-20％Fe3O4在扫描电镜下呈海绵状,分布均匀,磁性随材料体积增大而增大.体外加热实验结果显示,随时间延长,温度逐渐升高,在间隔加热条件下PLGA-60％NdFeB-20％Fe3O4趋于稳定.随加热时间延长,牛肝块消融体积、范围逐渐扩大,加热3 min时消融体积达(2.34±0.25)cm3.动物实验表明,肿瘤表面皮肤在治疗后第2天开始结痂,20天后创面开始愈合,CEUS示热消融后肿瘤组织内几乎无造影剂充填.HE染色示治疗组肿瘤细胞发生明显凝固性坏死,而对照组肿瘤体积逐渐增大.结论 在高频交变磁场作用下,PLGA-60％ NdFeB-20％ Fe3O4原位植入物可产生明显热效应,间隔加热时可有效消融裸鼠MDA-MB-231乳腺癌.
