小粒径磁共振成像超敏感纳米对比剂的研制及初步动物实验

目的 制备一种小粒径磁共振成像(MRI)超敏感的纳米对比剂并进行初步动物实验,探讨其用于分子影像学研究的可行性.方法 利用聚乙二醇(PEG)引发ε-己内酯(CL)开环聚合与自组装技术制备嵌段聚合物PEG-b-PCL,在其疏水性内核负载单颗粒超顺磁性氧化铁(SPIO)制成纳米对比剂.应用透射电子显微镜测量该纳米对比剂的粒径,原子吸收法测量其SPIO负载率,多平面回波SE序列测量T2值并计算横向弛豫率R2,同时对其进行磁学性质测量.将纳米对比剂由鼠尾静脉注射入Balb/c裸鼠体内,利用MRI于注射前、注射后1、3、6、12、24 h共6个时间点进行扫描,观察其在裸鼠体内的分布特点及循环时间.结果 制备的纳米对比剂粒径为(38±3)am,Fe3O4含量为37.0％,横向弛豫率R2为110 Fe(mmol/L)-1·s-1;磁学性质测定结果表明其具有超顺磁性.经外周静脉注射后,主要分布于肝脏,且循环时间长,与注射前相比,1 h信号强度明显降低(498±60比120±32,P＜0.05),至24 h降低至88+28(P＜0.05).结论 负载单颗粒SPIO的聚合物纳米对比剂粒径小、MRI超敏感,具有成为MRI对比剂并用于分子靶向成像的潜能.     

叶酸受体介导的肿瘤靶向超顺磁性纳米胶束的制备及体外实验

目的探讨叶酸受体介导的两亲聚合物纳米胶束对人肝癌Bel 7402细胞的靶向性，及利用MR仪对其进行监测的可行性。方法制备由叶酸修饰的、载有超顺磁性氧化铁（SPIO）及抗癌药物表阿霉素（DOX）的纳米胶束，将叶酸靶向及非叶酸靶向纳米胶束分别与人肝癌Bel 7402细胞共孵育1h，进行普鲁士蓝染色和流式细胞术观察Bel 7402细胞对叶酸靶向及非叶酸靶向纳米胶束的吸收情况，并体外MRI观察T2WI信号强度变化。结果叶酸靶向纳米胶束与Bel 7402细胞共孵育后普鲁士蓝染色显示细胞内大量铁存在；非叶酸靶向纳米胶束普鲁士蓝染色显示细胞内铁浓度极低。流式细胞术显示叶酸靶向组及非叶酸靶向组的平均荧光强度分别为117．88和46．33，叶酸靶向组约为非叶酸靶向组的2．5倍。体外MRI显示叶酸靶向纳米胶束与Bel 7402细胞共孵育后在T2WI上信号明显降低（SPIO浓度为5、10、20、40和80μg／ml时，信号变化率中位数分别为-5．02％、-23．58％、-45．89％、-70．34％和-92．41％），而非叶酸靶向组在T2WI上信号无明显降低（SPIO浓度为5、10、20、40和80μg／ml时信号变化率中位数分别为-3．77％、-2．16％、-2．18％、-2．74％和-19．77％）。体外竞争抑制实验普鲁士蓝染色显示细胞内铁浓度极低。结论以叶酸修饰的生物可降解聚合物纳米胶束对人肝癌细胞Bel 7402有较好的靶向性，使用临床型MR仪可对其进行监测。     

小粒径磁共振成像超敏感纳米对比剂的研制及初步动物实验

Objective To synthesize a small size and super-sensitive magnetic resonance imaging (MRI) nano-contrast agent for preliminary animal experiment and to explore the feasibility for its use in molecular imaging studies.Methods Polyethylene glycol (PEC) was used for ring-opening polymerization of ε-caprolactone(CL), and amphiphilic PEG-b-PCL block polymer was prepared by self-assembly technique.Single particle superparamagnetic iron oxide (SPIO) was loaded at the hydrophobic core of PEG-b-PCL to develop a nano-contrast agent.The particle diameter and SPIO-loading density were respectively determined by transmission electron microscope and atomic absorption spectroscopy.Echo multiplanar sequence was used for T2 value test, with transverse relaxation rate R2 computed.Meanwhile, magnetic properties were tested.After intravenous injection via caudal vein of Balb/c nude mice, the distributions and circulation time of this nano- particle were analyzed using MRI scanner at before injection and lh, 3h, 6 h, 12 h and 24 h after injection.Results The micelle diameter was around (38+3) nm and the content of Fe3O4 (wt%) was 37.0%.The transverse relaxation rate R2 was 110 Fe(mmol/L)-1 ·s-1.Superparamagnetism was observed in magnetic property test.After intravenous injection, the nano-particles were mainly distributed in the liver with a long circulation time.Signal intensity at 1 h decreased significantly when compared with that of before injection (120±32 vs 4986±0, P＜0.05) , and then decreased to (88±28) at 24 h (P＜0.05).Conclusion The nanometer micelle loaded with single SPIO particle demonstrates its potential as a powerful MRI contrast agent for molecular imaging studies because of its small size and high sensitivity.