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.     

超微超顺磁性纳米氧化铁标记犬口腔黏膜上皮细胞与磁共振成像实验

BACKGROUND: Epithelial cells are commonly used as the seed cell in tissue engineering; however, there is still a lack of an effective in vivo noninvasive trace technology. OBJECTIVE: To investigate the feasibility of labeling canine oral epithelial cells with ultrasmall superparamagnetie iron oxide (USPIO) and magnetic resonance imaging (MRI) in vitro.  METHODS: Oral epithelial cells from beagles were primary cultured, and then labeled by 0.75 mg/L poly-L-lysine combined with USPIO (0, 5, 10, 25, 50 and 100 mg/L), respectively. To determine the optimal dosage, the intracellular iron expression was identified by Prussian blue staining, and the cell viability in different groups was detected by cell counting kit-8. Finally, 2×105 labeled cells were suspended with 1 mL PBS buffer, and were screened using 3.0 T MR on T2*WI sequences in vitro.  RESULTS AND CONCLUSION: USPIO prepared with 0.75 mg/L poly-L-lysine could successfully label dog oral epithelial cells. Prussian blue staining showed intracellular blue spots, and the intracellular blue spots became more with the concentration increasing and saturated at the concentration of 25 mg/L. Cell counting kit-8 indicated that the cell viability did not change when the concentration < 25 mg/L. Among the T2*WI sequences, the MRI signal intensity decreased with the concentration increasing. In conclusion, canine oral epithelial cells can be effectively labeled with USPIO making no impact on cell viability when the concentration < 25 mg/L, and MRI can be used to track these labeled cells in vitro．     

超顺磁性氧化铁增强的磁共振成像在肝占位病变诊断中的价值

肝脏占位病变的检出与定性一直是影像学研究的重点与难点之一。CT、磁共振(MRI)的问世,使这一领域有了突飞猛进的发展。但某些占位病变,在常规CT、MRI平扫和增强扫描中与正常肝组织之间密度／信号差较小而易漏诊及误诊或定性困难。为弥补这一不足,各种用于肝脏的特异性对比剂应运而生,超顺磁性氧化铁(SPIO)就是其中之一。自     

磁共振对超顺磁性氧化铁标记的大鼠间充质干细胞成像的研究

目的:探讨磁共振对超顺磁性氧化铁(SPIO)纳米颗粒体外标记大鼠间充质干细胞进行成像的可行性.方法:多聚赖氨酸修饰的Fe3O4纳米颗粒.分别培养大鼠间充质干细胞至对数生长期,更换为分散多聚赖氨酸修饰的Fe3O4纳米颗粒的培养液,取所培养的细胞进行电镜超微结构观察.磁共振T1WI、FSE T2WI、FIESTA T2*WI三个序列对培养6 h的细胞群成像.结果:同一条件下培养6 h.见有多聚赖氨酸修饰的Fe3O4纳米颗粒进入大鼠间充质干细胞的细胞质内.对培养6h的细胞群磁共振成像中.标记后的大鼠间充质干细胞在FSE T1WI、FSET2WI、FIESTA T2WT三个序列中均可显示SPIO信号.其中在FSE T2WI上各标记细胞的EP管信号均较T1WI信号改变明显.结论:超顺磁性氧化铁纳米颗粒可以标记大鼠间充质干细胞,应用磁共振可以对其进行监测.     

负载超顺磁性氧化铁颗粒聚合物纳米囊泡的制备及MR成像

目的 制备负载油性、水性超顺磁性氧化铁(SPIO)颗粒聚合物纳米囊泡,并观察其表征和MRI成像特点.方法 经多步化学反应得到共聚物聚乙二醇-聚(D,L-丙交酯)(PEG-PDLLA),通过多次乳化及溶剂挥散法使共聚物在水溶液中自组装成囊泡,并分别负载油性和水性SPIO.使用扫描电镜和透视电镜观察负载油性、水性SPIO聚合物纳米囊泡的直径、形态、分布,并用MRT2 mapping软件测量单纯SPIO水溶液、负载油性、水性SPIO聚合物纳米囊泡的T2弛豫率(1/T2).溶液浓度分别取原液、原液的1/2、1/4、1/8、1/16、1/32.结果 负载油性SPIO和水性SPIO聚合物纳米囊泡的的平均直径分别为( 182.2 ±23.9) nm、(191.7 ±28.7) nm.电镜显示油性SPIO均匀地分散于囊泡的中心膜上;水性SPIO以团簇的形式被包裹在囊泡的内腔中.负载SPIO的聚合物囊泡比单纯SPIO水溶液表现更高MRI敏感性.在相同铁离子浓度下,负载水性SPIO聚合物囊泡的T2弛豫率(1/8浓度时为4.60)高于负载油性SPIO聚合物纳米囊泡(1/8浓度时为2.85).结论 负载SPIO聚合物纳米囊泡比单纯SPIO水溶液表现出更高的MRI敏感性,负载水性SPIO聚合物囊泡的T2弛豫率高于负载油性SPIO聚合物纳米囊泡.     

SPIO结构,功能及应用浓度研究新进展

超顺磁性氧化铁（SPIO）具有典型的晶体结构,有效成分是Fe3O4晶体核心,其作为纳米粒子,常包被葡聚糖右旋糖酐或其他物质而具有一定的水溶性或生物活性。Fe3O4具有极强铁磁性和超顺磁性,能缩短周围氢质子的弛豫时间,降低正常组织的信号强度,使T2加权图像信号明显下降,SPIO因能被网状内皮系统所摄取而已被用作临床磁共振成像（MRI）T2加权造影剂;同时,SPIO也可被组织中不同类型细胞所摄取的浓度的不同而显示出不同的影像学差异,因此SPIO的应用浓度对细胞的活性及MRI效应有着重要的影响。本文就相关进展做一综述。     

超顺磁性氧化铁纳米颗粒体外标记兔骨髓间充质干细胞的安全性以及MRI成像特征*☆

背景：传统的干细胞标记方法常需要病理组织学等侵袭性手段检测,无法动态观察整个实验过程,也不适合临床研究。 目的：观察超顺磁性氧化铁纳米颗粒体外标记对兔骨髓间充质干细胞生物学特性的影响以及标记兔骨髓间充质干细胞的体外MRI成像特征。 方法：采用红细胞裂解贴壁法培养扩增兔骨髓间充质干细胞。采用不同浓度超顺磁性氧化铁纳米颗粒(100,50,25,12.5 mg/L)联合多聚赖氨酸(0.75 mg/L)标记兔骨髓间充质干细胞。对标记兔骨髓间充质干细胞进行MRI检测,观察其成像特征。 结果与结论：25 mg/L的超顺磁性氧化铁纳米颗粒联合0.75 mg/L多聚赖氨酸标记兔骨髓间充质干细胞具有较好的安全性和有效性。此浓度对细胞的生长活性没有影响,不影响骨髓间充质干细胞的成骨成脂分化能力。MRI扫描在T2*WI序列上能明显有效地显像超顺磁性氧化铁纳米颗粒标记的兔骨髓间充质干细胞。 关键词：超顺磁性氧化铁纳米颗粒;骨髓间充质干细胞;标记;磁共振;安全性 doi:10.3969/j.issn.1673-8225.2012.06.001     

超顺磁性氧化铁微粒磁标记骨髓间充质干细胞效率实验研究

目的探讨不同浓度超微超顺磁性氧化铁微粒（USPIO）与多聚左旋赖氨酸（PLL）标记大鼠骨髓问充质十细胞（BMSCs）的磁标记效率及对细胞生长活力的影响,寻找最佳配比浓度。方法实验采用6周龄Wister近交系大鼠,150g芹右．雄性。用贴壁法分离培养BMSCs。使用6nmUSPIO—PLL复合物标记BMSCs。实验分6组,对照组为未标记的BMSCs（A组）。按照PLL的有无及PLL质量浓度梯度（0、0．25、0．50、0．75、1．00μg／mL）分为5个实验组（B～F组）;其中每个实验组再根据不同浓度铁离子与PLL结合（USPIO的终质量浓度分别为25、50、100、150μg/mL）。使用电子显微镜及光学显微镜观察标记后的BMSCs及BMSCs内的USPIO微粒。BMSCs活力测定采用台盼蓝排除实验。BMSCs生长曲线绘制采用MTT法。MRI观察体外标记后BMSCs的显影。火焰法测量BMSCs内铁含量,验证铁含量与MRI信号的关系。统计学分析采用方差分析。,结果台盼蓝染色证实90％以上标记后BMSCs均拒染台盼蓝。根据BMSCs生长曲线判断单纯使用铁离子质量浓度达到200μg／mL时或PLL用量达1．00μg／mL会对BMSCs的生长产生一定的抑制作用。火焰法测得单独USPIO标记BMSCs与USPIO—PLL标记BMSCs铁含量差异有统计学意义（P〈0．05）。T2WI及SWI序列图像从B组至F组信号强度逐级下降,反映出铁离子的变化情况。结论使用USPIO（100μg／mL）结合PLL（0．75μg／mL）标记BMSCs即对细胞活性和生长无不利影响．且标记BMSCs的信号强度较强。     

超顺磁性氧化铁的合成及其对细胞标记相关研究进展

细胞移植在修复损伤组织等方面具有极大的前景.应用细胞治疗常规治疗效果不佳的疾病或建立更为优化的治疗方案,移植细胞的在体连续动态追踪显得尤为重要.超顺磁性氧化铁(SPIO)的应用,改善了以往只能依靠免疫组织化学、电镜等侵袭性方法的不便.研究者建立了多种制备该颗粒的方法,并摸索其标记细胞的最佳条件,通过动物实验,证实了SPIO活体示踪细胞的可行性及其优势,为细胞移植运用于临床治疗及疗效评价提供了可靠手段.     

钆螯合物磁共振成像对比剂的研究进展

在综合文献的基础上,对新型细胞外、肝特异性、网状内皮系统特异性、血池和其它组织特异性钆螯合物磁共振对比剂的研究进展作了较详细的介绍。提示新型组织特异性钆螯合物磁共振对比剂更安全更有效,也是当前钆螯合物磁共振对比剂研究的发展方向。     

Muscle cross-section measurement by magnetic resonance imaging

Summary Muscle cross-section areas were measured by magnetic resonance imaging (MRI) in the thigh of a human cadaver,. the results being compared with those obtained by photography of corresponding anatomic macroslices. A close correlation was found between MRI and photographic evaluation, differences between the methods ranging from nil to 9.5%, depending on the scan position and the muscle groups. In vivo MRI measurements were performed on 12 female and 16 male students, the objectivity, the test-retest reliability and the variability of the MRI measurements being studied by fixing the scan position either manually or by coronary scan. The latter method appeared to be more objective and reliable. The coefficients of variation for muscle cross-section areas measured by MRI were in the range of those for the planimetry of given cross-section areas. Allowing for differentiation between several small muscle bundles in a given area, MRI proved to be a suitable method to quantify muscle cross-sections for intra- and interindividual analysis of muscle size.     

Anatomic correlation of cadaver cryomicrotomy with magnetic resonance imaging

Summary The performance of frozen sections of a thickness varying between 5 and 50 m in fresh undecalcified cadaveric human specimens was perfected in Sweden by one of the authors in 1983. This technique makes it possible to obtain anatomic images of high definition which were correlated with MRI sections made at intervals of 20 m.

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Corrélations anatomiques entre la cryomicrotomie sur cadavre et l'IRM

Résumé La réalisation de coupes congelées dont l'épaisseur varie entre 5 et 50 m, sur prélèvements cadavériques humains frais et non décalcifiés a été mise au point en Suède par l'un des auteurs en 1983. Cette technique permet d'obtenir des images anatomiques de haute définition qui ont été corrélées avec des coupes en IRM réalisées à des intervalles de 20 m.

     

Self-assembled magnetic fluorescent polymeric micelles for magnetic resonance and optical imaging

Stable and cytocompatible hybrid PEGylated micelles with multimodal imaging capabilities are described. The F₃O₄-encapsulated polymeric micelles composed of cores containing magnetic nanoparticles and polyethylene glycol (PEG) shells are synthesized by self-assembly of amphiphilic poly(HFMA-co-VBK)-g-PEG copolymers and oleic acid stabilized Fe₃O₄ nanoparticles. The Fe₃O₄ magnetic nanoparticles in the core produce T₂-weighted MR imaging functionalities, whereas the small fluorescent monomer carbazole in the polymer shell introduces good fluorescent properties. The multifunctional micelles exhibit excellent paramagnetic properties with the maximum saturation magnetization of 9.61 emu/g and transverse relaxivity rate of 157.44 mm⁻¹ S⁻¹. In vivo magnetic resonance imaging (MRI) studies reveal enhanced contrast between the liver and spleen. Fluorescence spectra show characteristic emission peaks from carbazole at 350 nm and 365 nm and vivid blue fluorescence can be observed by 2-photon confocal scanning laser microscopy (CLSM). In vivo optical imaging demonstrates the unique fluorescent characteristics of the Fe₃O₄-encapsulated polymeric micelles in the liver and spleen and the excellent multifunctional properties suggest potential clinical use as nanocarriers in magnetic resonance imaging and optical imaging.     

咀嚼时局部脑活动的功能性核磁共振成像

目的：应用功能性核磁共振成像（fMRI）探测人吸嚼时的大脑功能活动。方法：要求人在无任何其它躯体活动条件下咀嚼肌以10s运动20s休息的频率进行。选用8例成人冠状切面和横轴面的头部磁共振片,观察脑功能活动情况。结果：①在咀嚼时脑的广泛区域是激活的;②在相对应的咀嚼活动中有优势半球的激活区;③第I躯体感觉区激活的方式远较第I躯体运动区多样化;④在额叶中4例年轻观察对象出现了广泛的神经元激活区,但在老年人很少出现这样的激活区。结论：咀嚼活动除了它本身的功能运动外,在维持脑的活动方面具有重要的作用。同时也说明fMRI在研究活体人脑功能活动方面是一个相当有效的方法。     

Non-invasive temperature imaging of muscles with magnetic resonance imaging using spin-echo sequences

The application of spin-echo magnetic resonance imaging sequences on non-invasive temperature imaging for temperature mapping of human limbs is investigated. In an in vitro expriment performed on a meat sample, the equilibrium magnetisation P and the spin-lattice relaxation time T₁ are calculated from the values for the repetition time TR and the signal intensities obtained by a spin-echo sequence at different tissue temperatures tures as measured by a fibre-optic probe. T₁ is linearly correlated to the tissue temperature, and P is linearly correlated to the reciprocal value of the absolute temperature. Both effects, taken together, lead to a non-linear dependency of the signal intensity on temperature. Therefore a TR leading to maximum temperature dependency of the signal intensity is calculated and used in the futher experiments. In the in vivo experiments, the lower legs of two volunteers are cooled from outside. Images are acquired with a spin-echo sequence (1.5T, TR=1200 ms, TE=10 ms). A rise in signal intensity in the muscle with falling skin temperature is observed, particularly in more peripheral muscle layers. This study shows that spin-echo sequences can be used to monitor temperature changes and temperature differences in living muscle tissue.     

Factors affecting perceived tumor volumes in magnetic resonance imaging

Irregularly structured brain tumors, such as glioblastomas, challenge attempts to visualize and quantify their three-dimensional structure. Magnetic resonance imaging (MRI) represents one tool for attempting to noninvasively track tumor size. MR images demonstrate widely varying perceived tumor margins. In addition, adjunct therapies, such as the administration of steroids, greatly affect the volumes perceived in images formed by certain pulse sequences. In this study tumors were grown in 15 dogs and the tumor size tracked for a period of time. The dogs were placed on dexamethasone for a week and another series of scans was obtained. No other therapies were provided. The data for visualized tumor size are provided for T₁, T₂, and proton density. Weighted images are provided and the relationships between the scans are discussed.     

Iron oxide/manganese oxide co-loaded hybrid nanogels as pH-responsive magnetic resonance contrast agents

This work described a proof of concept study of hybrid nanogel-based magnetic resonance contrast agents, SPIO@GCS/acryl/biotin@Mn-gel, abb. as SGM, for highly efficient, pH-responsive T₁ and T₂ dual-mode magnetic resonance imaging (MRI). SGM have been synthesized by assembling superparamagnetic iron oxide particles into polysaccharide nanoclusters, followed by in-situ reduction of the manganese species on the clusters and a final mild polymerization. The dual-mode SGM showed an interesting pH-responsiveness in in vitro MRI, with both T₁ and T₂ relaxivities turned “ON” in the acidic environment, along with an increase in the r₁ and r₂ relaxivity values by 1.7-fold (from 8.9 to 15.3 mM⁻¹ S⁻¹) and 4.9-fold (from 45.7 to 226 mM⁻¹ S⁻¹), due to desirable silencing and de-silencing effects. This interesting acidic-responsiveness was further verified in vivo with both significantly brightened signal of tumor tissue in T₁-weighted MR images and a darkened signal in T₂-weighted MR images 50 min post-injection of SGM. This smart hybrid nanogel may serve as a promising candidate for further studies of dual-mode (T₁ and T₂) contrast agents in MRI, due to its high stability, interesting pH-response mechanism and indicative imaging of tumors.