聚乙二醇/聚乙烯亚胺修饰的超顺磁性氧化铁磁共振造影剂的性能

以聚乙烯亚胺(PEI)为添加剂,在聚乙二醇(PEG)中高温热分解乙酰丙酮铁(Fe(acac)3),合成了超顺磁性氧化铁(SPIO)纳米粒子。采用X射线粉末衍射仪(XRD)、透射电子显微镜(TEM)、高分辨透射电镜(HRTEM)、超导量子干涉仪(SQUID)、热重分析仪(TGA)、傅里叶变换红外光谱仪(FT-IR)、纳米粒度与Zeta电位分析仪及小动物7T磁共振扫描仪对样品进行表征。结果表明,高温热分解法合成的粒子近似等轴晶形,当反应温度由180℃升高到260℃,粒径由(5.2±1.0)nm增加到(10±1.7)nm,并且结晶度增高,在室温下具有超顺磁性和高饱和磁化强度。PEG和PEI共同修饰于SPIO纳米粒子表面,使其在水溶液中能够长时间(90 d以上)稳定分散。在260℃下制备的纳米粒子,其磁共振弛豫T1和T2加权成像显示较好的对比效果,纳米粒子的纵向弛豫率r1为1.65 mmol·L-1·S-1,横向弛豫率r2为142.99 mmol·L-1·S-1,得到一个较高的r2/r1值,为86.6,生物体内成像实验表明所制备的纳米粒子可以作为一种优异的T2造影剂。     

垂直排列ReS2(1-x)Se2x合金纳米片的控制合成及带隙调控

二维过渡金属硫属化合物具有优异的电学和光学特性, 形貌控制及带隙调控对于其在光电子学、光子学、纳米电子学领域中的应用至关重要。研究采用CVD技术在SiO₂/Si衬底上生长了垂直排列ReS₂纳米片材料, 硒化处理后得到ReS_2(1-x)Se_2x合金纳米片, 并研究了硒化温度(700、850 和 920℃)及硒化时间(0.5、1和1.5 h)对ReS_2(1-x)Se_2x合金纳米片形貌及组分的影响。XPS元素定量分析及紫外-可见-近红外吸收光谱研究表明ReS_2(1-x)Se_2x样品中Se含量可以在x=0(纯ReS₂)到x=0.86之间调变, 相应材料的带隙可从1.55 eV (800 nm)调变到1.28 eV (969 nm)。SEM结果显示ReS_2(1-x)Se_2x纳米片的结构受到硒化温度和硒化时间的影响, 硒化温度升高和硒化时间延长会破坏纳米片的垂直结构。上述结果表明本研究成功合成了垂直排列ReS_2(1-x)Se_2x合金纳米片, 该材料在电化学催化、功能电子器件和光电子器件方面具有潜在应用价值。     

磁性碳纳米管的制备及其在肿瘤细胞光热疗与磁共振成像中的应用

肿瘤是目前最主要的致死原因之一，实现对肿瘤的精准和非侵入性高效诊疗具有重要意义。以具有极高长径比、易于穿透细胞膜并具有优异生物相容性的碳纳米管(CNTs)作为载体，以乙酰丙酮铁为铁源，通过溶剂热法在其表面原位生长具有超顺磁特性的四氧化三铁纳米粒子(Fe₃O₄ NPs)，制备了具有优异水分散稳定性的磁性碳纳米管复合纳米材料。结果表明该磁性碳纳米管具有较高的近红外光热转换性能，在50μg·mL^-1浓度下808 nm激光照射10 min即可升温至48.6℃，且具有良好的光热稳定性。细胞及成像实验结果表明该复合纳米材料具有较好的生物相容性并对人宫颈癌细胞(HeLa)具有优异的光热杀伤效果，在体外模拟肿瘤微环境中磁共振成像(MRI) T₂弛豫率r₂可达215.61 mmol^-1·L·s^-1，表明制备的磁性碳纳米管具有出色的生物安全性、磁性和光热特性，有望用于磁靶向的肿瘤光热疗与磁共振成像的一体化诊疗。     

二肉豆蔻酰磷脂酰胆碱修饰的氧化铁纳米粒子在PC-12细胞内的分布

有机物包覆的超顺磁性氧化铁纳米粒子(Superparamagnetic iron oxide nanoparticles,SPIONs)因具有良好的水溶性和生物相容性而被越来越多地用作生物医学研究的工具。采用简便的高温热分解法合成聚乙二醇(Polyethylene glycol,PEG)和聚乙烯亚胺(Polyethyleneimine,PEI)修饰的超顺磁性氧化铁纳米粒子(PEG/PEI-SPIONs),再在其表面通过氢键相互作用接枝二肉豆蔻酰磷脂酰胆碱(1, 2-dimyristoyl-sn-glycero-3-phosphocholine, DMPC),成功制备了DMPC-SPIONs。由热重结果分析可知DMPC的接枝率约为31.7%(质量分数)。将PEG/PEI-SPIONs和DMPC-SPIONs分别与PC-12细胞孵化,对孵化后的细胞进行表征和分析发现,大量的DMPC-SPIONs进入了细胞,而PEG/PEI-SPIONs进入细胞内的量较少。这表明DMPC对于氧化铁纳米粒子进入细胞起到关键作用。通过透射电镜观察与DMPC-SPIONs孵化的PC-12细胞发现,氧化铁纳米粒子密集分布于溶酶体、线粒体、内质网和细胞核膜表面,另外,也有一部分DMPC-SPIONs分布在细胞膜上的纤毛附近,并观察到细胞膜对纳米粒子的内吞现象。DMPC-SPIONs良好的膜透过性及在胞内细胞器的密集分布使其在磁热疗、磁共振成像、药物输运等生物医学领域具有广阔的应用前景。     

混合属性广义灰靶决策方法的模式识别功能研究

为研究混合属性广义灰靶决策方法的模式识别功能，根据其具有靶心指标可变动，决策依据（靶心距）具有开放性、可扩充的特点提出了可用于模式识别的理论框架。该理论框架首先确定标准模式的特征及待识别目标，分别作为靶心指标向量和决策方案；其次，化各类混合属性值为二元联系数，并视为指标向量；然后，基于指标向量计算各待识别目标向量与靶心向量的接近度；最后，根据各待识别目标的综合接近度确定待识别目标的相应模式。应用分析表明，投资企业y₁和y₂与模式S₃和S₂的最小综合接近度分别为0. 427 0和0. 237 5；因此，企业y₁与y₂分别选择投资模式S₃和S₂是适宜的。     

静电喷雾法一步制备自显影Fe3O4@壳聚糖载药栓塞微球

采用静电喷雾法一步制备包裹着Fe₃O₄纳米粒子的壳聚糖复合微球(Fe₃O₄@CS微球),实现Fe₃O₄纳米粒子与微球同时合成。还可以按需制备粒径范围为90～1 000μm的Fe₃O₄@CS微球,以满足不同部位血管的临床栓塞要求。SEM显示微球形貌均匀且粒径分布均一((94±3)μm),体外降解实验证明了微球具有生物可降解性,磁共振成像测试表明所制备的Fe₃O₄@CS微球具有良好的临床成像能力,血液、细胞相容性评估证实Fe₃O₄@CS微球具有良好的生物相容性。负载盐酸阿霉素(DOX)的载药微球显示出典型的药物缓释曲线,72 h内DOX的累计释放率为28.82%。结果表明,这一步可控制备的自显影栓塞剂在经导管动脉栓塞术(TACE)未来应用中展示了巨大的潜力。     

Pd/PANI纳米纤维的液相合成及其对乙醇的电化学行为

以苯胺为单体、PdCl₂为金属前驱体、过硫酸铵为氧化剂,在避光条件下液相化学氧化合成Pd/PANI纳米纤维,用XRD、FESEM、TEM、SAED、HRTEM、FT-IR和UV-vis等手段对其表征,研究了 Pd/PANI纳米纤维修饰玻碳电极对乙醇的电化学行为。结果表明,Pd/PANI纳米纤维的平均直径为20 nm,长度为500 nm;平均直径为6 nm的纳米Pd颗粒单分散分布在PANI纤维中;Pd/PANI纳米纤维修饰电极的ECSA值为54.76 m²/g_Pd,是商用Pd/C催化剂(6.08 m²/g_Pd)的9倍,其j_f/j_b值为1.192。     

Bi2O3修饰的BiPO4纳米棒复合催化剂可见光光催化性能的研究

以Bi₂S₃纳米棒为模板合成了形貌可控的BiPO₄ 纳米棒复合光催化剂。在可见光辐射下, 该复合催化剂表现出优异的光催化降解亚甲基蓝(MB)的性能。UV-Vis漫反射谱结果表明: 催化剂经过Bi₂O₃修饰后对可见光有很好吸收; X射线衍射仪和透射电镜等表征结果表明, 所制备的BiPO₄ 纳米催化剂为直径约30 nm、长约200~500 nm的纳米棒。表面修饰少量Bi₂O₃可明显促进光催化剂对亚甲基蓝(MB)的可见光降解效率, 其活性是未修饰催化剂的1.7倍。光电流和N₂吸附实验也表明表面修饰后的催化剂光电流和BET比表面积都明显增加。这可能是由于表面修饰的Bi₂O₃不仅显著提高了BiPO₄ 纳米棒复合催化剂的可见光吸收, 而且在BiPO₄表面起到了富集电子和传输电子的作用。结果表明表面修饰Bi₂O₃的BiPO₄ 纳米棒是一种高活性的光催化材料。     

溶剂热法合成Fe3O4纳米微粒及其调控机制

为探究磁性四氧化三铁(Fe₃O₄)纳米微粒的合成过程,采用溶剂热法制备Fe₃O₄纳米微粒并对其反应条件进行调控,通过扫描电子显微镜、红外光谱仪和X射线衍射仪分别对其表面形态、成分结构和晶体结构进行表征,利用振动样品磁强计测试其磁性能;研究反应时间、反应温度和聚乙二醇(PEG)用量的调控机制。结果表明,反应时间12 h、反应温度200℃、PEG含量1 mmol为最优合成条件;在该条件下制得的产物尺寸均一、形态稳定且具有良好的分散性,主体粒径在400 nm左右,且具有良好的磁性能。     

多肽或转铁蛋白接枝的氧化铁纳米粒子的制备及表征

以聚乙二醇(PEG)为还原剂、溶剂和修饰剂,将乙酰丙酮铁(Fe(acac)_3)高温热分解合成超顺磁性氧化铁纳米粒子(Superparamagnetic iron oxide nanoparticles,SPIONs)。透射电镜(TEM)结果显示:纳米粒子形状规则,分布均匀,平均粒径为7.5±1.0 nm。XRD结果表明样品主相为结晶良好的Fe_3O_4。通过将SPIONs表面修饰的PEG与马来酸酐(Mal)结合,再借助EDC-NHS的方法,分别与多肽(angiopep-2,ANG)或转铁蛋白(transferrin,Tf)接枝。结果表明:修饰ANG的SPIONs的水合动力学粒径为42 nm,zeta电位为-9.9 mV,ANG的修饰量为19 wt%,饱和磁化强度为58emu/g;修饰Tf的SPIONs的水合动力学粒径为96 nm,zeta电位为2.3 mV,Tf的修饰量为10 wt%,饱和磁化强度为43 emu/g。红外分析表明ANG或Tf分别共同修饰在SPIONs表面。修饰物使纳米粒子具有良好了水分散性。本工作为SPIONs应用于生物医学研究建立了材料基础。     

Synthesis,self-assembly,and characterization of PEG-coated iron oxide nanoparticles as potential MRI contrast agent

Aim: Investigated the self-assembly and characterization of novel antifouling polyethylene glycol (PEG)-coated iron oxide nanoparticles as nanoprobes for magnetic resonance imaging (MRI) contrast agent. Method: Monodisperse oleic acid-coated superparamagnetic iron oxide cores are synthesized by thermal decomposition of iron oleate. The self-assembly behavior between iron oxide cores and PEG-lipid conjugates in water and their characteristics are confirmed by transmission electron microscope, X-ray diffraction, thermogravimetric analysis, Fourier transform infrared spectroscopy, and vibrating sample magnetometer. Result: Dynamic light scattering shows superparamagnetic iron oxide nanoparticles coated with PEG are stable in water for pH of 3–10 and ionic strengths up to 0.3 M NaCl, and are protein resistant in physiological conditions. Additionally, in vitro MRI study demonstrates the efficient magnetic resonance imaging contrast characteristics of the iron oxide nanoparticles. Conclusion: The result indicates that the novel antifouling PEG-coated superparamagnetic iron oxide nanoparticles could potentially be used in a wide range of applications such as biotechnology, MRI, and magnetic fluid hyperthermia.     

Gold-coated iron oxide nanoparticles as a T2 contrast agent in magnetic resonance imaging

Gold-coated iron oxide (Fe3O4) nanoparticles were synthesized for use as a T2 contrast agent in magnetic resonance imaging (MRI). The coated nanoparticles were spherical in shape with an average diameter of 20 nm. The gold shell was about 2 nm thick. The bonding status of the gold on the nanoparticle surfaces was checked using a Fourier transform infrared spectrometer (FTIR). The FTIR spectra confirmed the attachment of homocysteine, in the form of thiolates, to the Au shell of the Au-Fe3O4 nanoparticles. The relaxivity ratio, R2/R1, for the coated nanoparticles was 3-fold higher than that of a commercial contrast agent, Resovist, which showed the potential for their use as a T2 contrast agent with high efficacy. In animal experiments, the presence of the nanoparticles in rat liver resulted in a 71% decrease in signal intensity in T2-weighted MR images, indicating that our gold-coated iron oxide nanoparticles are suitable for use as a T2 contrast agent in MRI.     

Surface Functionalization of Single Superparamagnetic Iron Oxide Nanoparticles for Targeted Magnetic Resonance Imaging

Magnetic resonance imaging (MRI), a non‐invasive, non‐radiative technique, is thought to lead to cellular or even molecular resolution if optimized targeted MR contrast agents are introduced. This would allow diagnosing progressive diseases in early stages. Here, it is shown that the high binding affinity of poly(ethylene glycol)‐gallol (PEG‐gallol) allows freeze drying and re‐dispersion of 9 ± 2‐nm iron oxide cores individually stabilized with ≈9‐nm‐thick stealth coatings, yielding particle stability for at least 20 months. Particle size, stability, and magnetic properties of PEGylated particles are compared to Feridex, a commercially available untargeted negative MR contrast agent. Biotin‐PEG(3400)‐gallol/methoxy‐PEG(550)‐gallol stabilized nanoparticles are further functionalized with biotinylated human anti‐VCAM‐1 antibodies using the biotin–neutravidin linkage. Binding kinetics and excellent specificity of these nanoparticles are demonstrated using quartz crystal microbalance with dissipation monitoring (QCM‐D). These MR contrast agents can be functionalized with any biotinylated ligand at controlled ligand surface density, rendering them a versatile research tool.     

Inorganic Nanoparticles for MRI Contrast Agents

Various inorganic nanoparticles have been used as magnetic resonance imaging (MRI) contrast agents due to their unique properties, such as large surface area and efficient contrasting effect. Since the first use of superparamagnetic iron oxide (SPIO) as a liver contrast agent, nanoparticulate MRI contrast agents have attracted a lot of attention. Magnetic iron oxide nanoparticles have been extensively used as MRI contrast agents due to their ability to shorten T2* relaxation times in the liver, spleen, and bone marrow. More recently, uniform ferrite nanoparticles with high crystallinity have been successfully employed as new T2 MRI contrast agents with improved relaxation properties. Iron oxide nanoparticles functionalized with targeting agents have been used for targeted imaging via the site‐specific accumulation of nanoparticles at the targets of interest. Recently, extensive research has been conducted to develop nanoparticle‐based T1 contrast agents to overcome the drawbacks of iron oxide nanoparticle‐based negative T2 contrast agents. In this report, we summarize the recent progress in inorganic nanoparticle‐based MRI contrast agents.     

Structural Characterization and Magnetic Properties of Iron Oxides Biological Polymers

Iron oxide nanoparticles (IONs) coated with different biological (dextran, sucrose) polymers have been synthesized by the coprecipitation method. Biological polymers coated iron oxide nanoparticles were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM). Zero field cooled and field cooled magnetizations measurements are also reported. We present a preliminary study of the influence of biological polymer on the interaction effects in powders. The temperature, T _max, of the maximum, increased from 25 K (dextran) to 52 K (sucrose). These values are due to the decrease of interparticle interactions, mainly as a result of the interparticle distance increase.     

Synthesis and characterization of lanthanide-doped sodium holmium fluoride nanoparticles for potential application in photothermal therapy

Upconversion nanoparticles (UC NPs) in combination with plasmonic materials have great potential for cancer photothermal therapy. Recently, sodium holmium fluoride (NaHoF₄) is being investigated for luminescence and magnetic resonance imaging (MRI) contrast agent. Here, we present successful synthesis of excellent quality doped NaHoF₄ NPs for possible UC luminescence application and coated for possible photothermal therapy application. Synthesized NaHoF₄ nanocrystals were doped with Yb/Er and coated with gold, gold/silica, silver and polypyrrole (PPy). XRD, XPS and TEM were used to determine structure and morphology of the NPs. Strong UC photoluminescence (PL) emission spectra were obtained from the NPs when excited by near-infrared (NIR) light at 980 nm. Cell viability and toxicity of the NPs were characterized using pancreatic and ovarian cancer cells with results showing that gold/silica coating produced least toxicity followed by gold coating.     

Characterization of the biocompatible magnetic colloid on the basis of Fe3O4 nanoparticles coated with dextran, used as contrast agent in magnetic resonance imaging

The magnetic resonance imaging contrast agent, the so-called Endorem colloidal suspension on the basis of superparamagnetic iron oxide nanoparticles (mean diameter of 5.5 nm) coated with dextran, were characterized on the basis of several measurement techniques to determine the parameters of their most important physical and chemical properties. It is assumed that each nanoparticle is consisted of Fe3O4 monodomain and it was observed that its oxidation to gamma-Fe2O3 occurs at 253.1 degrees C. The M?ssbauer spectroscopy have shown a superparamagnetic behavior of the magnetic nanoparticles. The Magnetic Resonance results show an increase of the relaxation times T1, T2, and T2* with decreasing concentration of iron oxide nanoparticles. The relaxation effects of SPIONs contrast agents are influenced by their local concentration as well as the applied field strength and the environment in which these agents interact with surrounding protons. The proton relaxation rates presented a linear behavior with concentration. The measured values of thermo-optic coefficient dn/dT, thermal conductivity kappa, optical birefringence delta n0, nonlinear refractive index n2, nonlinear absorption beta' and third-order nonlinear susceptibility |chi(3)| are also reported.     

Intracellular Nanoparticle Coating Stability Determines Nanoparticle Diagnostics Efficacy and Cell Functionality

Iron oxide nanoparticles (NPs) are frequently employed in biomedical research as magnetic resonance (MR) contrast agents where high intracellular levels are required to clearly depict signal alterations. To date, the toxicity and applicability of these particles have not been completely unraveled. Here, we show that endosomal localization of different iron oxide particles results in their degradation and in reduced MR contrast, the rate of which is governed mainly by the stability of the coating. The release of ferric iron generates reactive species, which greatly affect cell functionality. Lipid‐coated NPs display the highest stability and furthermore exhibit intracellular clustering, which significantly enhances their MR properties and intracellular persistence. These findings are of considerable importance because, depending on the nature of the coating, particles can be rapidly degraded, thus completely annihilating their MR contrast to levels not detectable when compared to controls and greatly impeding cell functionality, thereby hindering their application in functional in vivo studies.     

一种新型球状纳米氧化铁的制备

以Fe(NO₃)₃·9H₂O为原料、以尿素为沉淀剂,用热解前驱体法制备出直径为40~60 nm的球状纳米氧化铁。使用XRD、SEM和EDS等手段对其表征,研究了Fe³⁺浓度、反应温度等因素对纳米氧化铁的粒径和形貌的影响、确定了球状纳米氧化铁的制备条件并分析了球状纳米氧化铁的形成机理。结果表明：随着Fe(NO₃)₃·9H₂O溶液温度的提高纳米氧化铁的结晶度随之提高、粒径增大。Fe(NO₃)₃·9H₂O的浓度对纳米氧化铁样品的粒度和形貌的影响不大。球状氧化铁纳米的形成机理是：铁源在水热条件下水解和结晶生成棕黄色絮状沉淀FeOOH,FeOOH在高温高压条件下溶解和再结晶生成了球状纳米氧化铁。     

Ag-assisted CeO2 catalyst for soot oxidation

In this work, the Ag loaded Ce-based catalyst was synthesized (by the sol−gel method) and its performance was studied by TG, H₂-TPR, XRD, SEM, TEM, BET and XPS. The results show that Ag nanoparticles be successfully loaded onto the CeO₂ surface and the relative content of Ag nanoparticles is about 10.22 wt.% close to the theoretical value (10%). XPS shows that Ag nanoparticles induce a great number of oxygen vacancies in the CeO₂ lattice through the electronic transfer, and H₂-TPR indicates that the Ag-assisted CeO₂ catalyst exhibits a better reduction performance and Ag nanoparticles can promote O⁻ transform into O²⁻. The catalytic activity for soot oxidation was studied by TG under air atmosphere and the activity was found to be obviously enhanced when Ag nanoparticles be load on the surface of CeO₂ (T₁₀ = 386 °C, T₉₀ = 472.5 °C, T_m = 431 °C). The reaction mechanism was also presented and O₂⁻ species is regarded as the determinant factor for the catalytic activity.