Study of DNA interaction with cobalt ferrite nanoparticles

Interaction of cobalt ferrite nanopowder and nucleic acid was investigated. Superparamagnetic cobalt ferrite nanoparticles (6-12 nm) were prepared by mechanochemical synthesis. Structure of the nanopowder was characterized using X-ray diffraction. It was shown that cobalt ferrite nanoparticles were associated with ssDNA and dsDNA in Tris-buffer resulting in bionanocomposite formation with mass weight relation nanoparticles: DNA 1:(0.083 +/- 0.003) and 1:(0.075 +/- 0.003) respectively. The mechanism of interaction between a DNA and cobalt ferrite nanoparticles was considered basing on the whole set of obtained data: FTIR-spectroscopy, analyzing desorption of DNA from the surface of the particles while changing the chemical content of the medium, and on the modeling interaction of specific biomolecule fragments with surface of a inorganic material. It was supposed that the linkage was based on coordination interaction of the phosphate groups and oxygen atoms heterocyclic bases of DNA with metal ions on the particle surface. These data can be used to design specific magnetic DNA-nanoparticles hybrid structures.     

Collective behaviour in two-dimensional cobalt nanoparticle assemblies observed by magnetic force microscopy

The use of magnetic nanoparticles in the development of ultra-high-density recording media is the subject of intense research. Much of the attention of this research is devoted to the stability of magnetic moments, often neglecting the influence of dipolar interactions. Here, we explore the magnetic microstructure of different assemblies of monodisperse cobalt single-domain nanoparticles by magnetic force microscopy and magnetometric measurements. We observe that when the density of particles per unit area is higher than a determined threshold, the two-dimensional self-assemblies behave as a continuous ferromagnetic thin film. Correlated areas (similar to domains) of parallel magnetization roughly ten particles in diameter appear. As this magnetic percolation is mediated by dipolar interactions, the magnetic microstructure, its distribution and stability, is strongly dependent on the topological distribution of the dipoles. Thus, the magnetic structures of three-dimensional assemblies are magnetically soft, and an evolution of the magnetic microstructure is observed with consecutive scans of the microscope tip.     

3D magnetic characterization of nanocrystalline cobalt thin films by combined magnetic force and Lorentz microscopy

Thin films of cobalt and cobalt-based compounds are recently popular for magnetic recording media because of their high recording density and great magnetic properties. Many techniques exist to image magnetic structures in thin films, nevertheless, none of them can furnish complete information about the magnetic details. In the present work the combined use of the information obtainable with Lorentz microscopy, performed in a transmission electron microscope (TEM), and of an atomic force microscope (AFM) working in the magnetic mode (MFM, magnetic force microscopy), both performed on the same specimen area, enabled, in a easy way, the study of the 3D magnetic structure of domains, of single cross-ties, the location of Bloch lines within a domain wall and the magnetic structure of magnetisation ripples. The 3D magnetic structure and contrast of nanocrystalline thin films of cobalt (100 nm thick), prepared by evaporation in high vacuum, were investigated at a spatial resolution of tens of nanometers.     

Magnetically Responsive Nanoparticles for Drug Delivery Applications Using Low Magnetic Field Strengths

The purpose of this study is to investigate the potential of magnetic nanoparticles for enhancing drug delivery using a low oscillating magnetic field (OMF) strength. We investigated the ability of magnetic nanoparticles to cause disruption of a viscous biopolymer barrier to drug delivery and the potential to induce triggered release of drug conjugated to the surfaces of these particles. Various magnetic nanoparticles were screened for thermal response under a 295-kHz OMF with an amplitude of 3.1 kA/m. Based on thermal activity of particles screened, we selected the nanoparticles that displayed desired characteristics for evaluation in a simplified model of an extracellular barrier to drug delivery, using lambda DNA/HindIII. Results indicate that nanoparticles could be used to induce DNA breakage to enhance local diffusion of drugs, despite low temperatures of heating. Additional studies showed increased diffusion of quantum dots in this model by single-particle tracking methods. Bimane was conjugated to the surface of magnetic nanoparticles. Fluorescence and transmission electron microscope images of the conjugated nanoparticles indicated little change in the overall appearance of the nanoparticles. A release study showed greater drug release using OMF, while maintaining low bulk heating of the samples ($T = 30$  $^circ$C). This study indicates that lower magnetic field strengths may be successfully utilized for drug delivery applications as a method for drug delivery transport enhancement and drug release switches.      

钴铁氧体纳米粒子制备及其镧掺杂的磁性能研究

为了制备性能良好的钴铁氧体及改善其磁性能,通过改进的溶胶凝胶自蔓延燃烧法成功地制备了钴铁氧体(CoFe2O4)及掺镧(La)钴铁氧体纳米粒子.采用X射线衍射(XRD),透射电镜(TEM)、能谱分析(EDS)、振动样品磁场计(VSM)对所得粒子进行了结构、形貌、成分及磁性能表征.测试结果表明,利用改进的溶胶凝胶法制得钴铁氧体粒度均匀,且成相温度较低,500℃煅烧1h时平均粒径12nm左右;通过掺杂稀土镧元素对所得铁氧体的相结构有较强的影响,所得掺镧钴铁氧体与目标产物一致;所得钴铁氧体具有较高的矫顽力(737.33Oe),并且通过稀土元素镧的掺杂提高了钴铁氧体的矫顽力.     

Cobalt nanoparticles coated with graphitic shells as localized radio frequency absorbers for cancer therapy

Graphitic carbon-coated ferromagnetic cobalt nanoparticles (C-Co-NPs) with diameters of around 7?nm and cubic crystalline structures were synthesized by catalytic chemical vapor deposition. X-ray diffraction and x-ray photoelectron spectroscopy analysis indicated that the cobalt nanoparticles inside the carbon shells were preserved in the metallic state. Fluorescence microscopy images and Raman spectroscopy revealed effective penetrations of the C-Co-NPs through the cellular plasma membrane of the cultured HeLa cells, both inside the cytoplasm and in the nucleus. Low radio frequency (RF) radiation of 350 kHz induced localized heat into the metallic nanoparticles, which triggered the killing of the cells, a process that was found to be dependent on the RF application time and nanoparticle concentration. When compared to carbon nanostructures such as single-wall carbon nanotubes, these coated magnetic cobalt nanoparticles demonstrated higher specificity for RF absorption and heating. DNA gel electrophoresis assays of the HeLa cells after the RF treatment showed a strong broadening of the DNA fragmentation spectrum, which further proved the intense localized thermally induced damages such as DNA and nucleus membrane disintegration, under RF exposure in the presence of C-Co-NPs. The data presented in this report indicate a great potential of this new process for in vivo tumor thermal ablation, bacteria killing, and various other biomedical applications.     

Polyethylenimine functionalized magnetic nanoparticles as a potential non-viral vector for gene delivery

Polyethylenimine (PEI) functionalized magnetic nanoparticles were synthesized as a potential non-viral vector for gene delivery. The nanoparticles could provide the magnetic-targeting, and the cationic polymer PEI could condense DNA and avoid in vitro barriers. The magnetic nanoparticles were characterized by Fourier transform infrared spectroscopy, X-ray powder diffraction, dynamic light scattering measurements, transmission electron microscopy, vibrating sample magnetometer and atomic force microscopy. Agarose gel electrophoresis was used to asses DNA binding and perform a DNase I protection assay. The Alamar blue assay was used to evaluate negative effects on the metabolic activity of cells incubated with PEI modified magnetic nanoparticles and their complexes with DNA both in the presence or absence of an external magnetic field. Flow cytometry and fluorescent microscopy were also performed to investigate the transfection efficiency of the DNA-loaded magnetic nanoparticles in A549 and B16-F10 tumor cells with (+M) or without (?M) the magnetic field. The in vitro transfection efficiency of magnetic nanoparticles was improved obviously in a permanent magnetic field. Therefore, the magnetic nanoparticles show considerable potential as nanocarriers for gene delivery.     

Preparation, Structure, and Properties of Magnetic Materials Based on Co-Containing Nanoparticles

The recent experimental data on the preparation and properties of materials containing Co-based magnetic nanoparticles are summarized. Particular attention is focused on the synthesis of cobalt nanoparticles in rigid matrices (polymers, metals, and solid surfaces) and their static magnetic properties, which are of great importance for practical applications. The conclusion is made that surface effects play an important role in determining the magnetic properties of nanoparticles.     

Magnetic Force Microscope Contrast Simulation for Low-Coercive Ferromagnetic and Superparamagnetic Nanoparticles in an External Magnetic Field

We report the results of simulations of magnetic force microscope (MFM) contrast for low-coercive ferromagnetic and superparamagnetic nanoparticles. We show that two types of MFM contrast in the form of gaussian and ring distributions can be observed because of probe-particle interaction. We discuss stabilization of the magnetic moment of nanoparticles by an external magnetic field. We have calculated the values of stabilizing magnetic fields and their dependence on probe parameters and scanning heights.     

钴铁氧体纳米管阵列制备及其磁学性能(英文)

为了研究一维钴铁氧体纳米管阵列的磁学性质,应用氧化铝模板具有的约束作用和毛细管作用,结合溶胶凝胶技术合成了钴铁氧体纳米管阵列.在140℃条件下,通过包含Fe(AO)3和Co(AO)2(物质的量之比为2∶1)的柠檬酸和乙二醇混合溶液(物质的量之比为1∶4)酯化反应得到溶胶.将氧化铝模板浸入溶胶几次后取出,取出充满溶胶的氧化铝模板,在大气气氛中,以0.6℃/min～5℃/min的升温速度将样品由室温升温至500℃,保温8 h.结果表明,在控制Fe3+离子浓度的条件下也可以合成钴铁氧体纳米线(Fe3+离子浓度大于1 mol/L)和"竹节"型纳米管(Fe3+离子浓度介于0.5 mol/L～1.0 mol/L),但重点进行了其纳米管阵列(Fe3+离子浓度小于0.5 mol/L)合成和磁学性能测试.透射电子显微镜(TEM)、高分辨电镜(HRTEM)的观察以及粉末X光衍射(XRD)测试结果表明纳米管组成为多晶结构.纳米管的直径取决于氧化铝模板的孔径,大约为200 nm,其长度约几个微米.应用样品振动磁强计对样品磁性进行了表征,结果表明纳米管阵列未表现出方向特性,矫顽力随着升温速率的降低而升高,在0.6℃/min的升温速率时,矫顽力达到最高的1 445 kOe,简单讨论了其形成原因.     

Quantitative measurement of the magnetic moment of individual magnetic nanoparticles by magnetic force microscopy

The quantitative measurement of the magnetization of individual magnetic nanoparticles (MNPs) using magnetic force microscopy (MFM) is described. Quantitative measurement is realized by calibration of the MFM signal using an MNP reference sample with traceably determined magnetization. A resolution of the magnetic moment of the order of 10(-18) A m(2) under ambient conditions is demonstrated, which is presently limited by the tip's magnetic moment and the noise level of the instrument. The calibration scheme can be applied to practically any magnetic force microscope and tip, thus allowing a wide range of future applications, for example in nanomagnetism and biotechnology.     

Nickel nanoparticles and nanowires obtained by scanning probe lithography using point indentation technique

A lithographic method of obtaining metal nanowires and nanoparticles on solid substrates is proposed, which employs a polymer mask with windows for the metal deposition formed by indentation in an atomic force microscope. Using this method, Ni nanowires with a minimum width of 60 nm, thicknesses within 6?C20 nm, and lengths up to 20 ??m and Ni nanoparticles with a preset ordered arrangement have been obtained on a SiO₂ surface. The domain structure in obtained nanoobjects has been studied by the magnetic force microscopy technique.     

利用均匀磁场提高聚乙烯亚胺-Fe3O4纳米颗粒复合物的磁转染效果

首次研究了不同均匀度磁场对磁转染效果的影响。测定了单边Halbach磁体和商品化96孔磁板的磁场均匀度。以化学共沉淀法制备聚乙烯亚胺(Polyethyleneimine,PEI)修饰的四氧化三铁(Fe_3O_4)纳米颗粒(PEI-Fe_3O_4),并用透射电子显微镜(TEM)、振动样品磁强计(VSM)、原子力显微镜、琼脂糖凝胶电泳等对其形貌、组成、DNA结合能力等进行表征。用倒置荧光显微镜、流式细胞术观察不同均匀度磁场下人肾上皮细胞(HEK293)对带有绿色荧光蛋白报告基因(GFP)的质粒pDNA(pAdTrackOK)的表达效果,并采用TEM观察PEI-Fe_3O_4磁性纳米颗粒进入细胞的过程。结果显示,所选取的两种磁场均匀度相差约100倍。制备的PEI-Fe_3O_4纳米复合物具有超顺磁性,对质粒pDNA(pAdTrack-OK)有较好的复合能力,其最佳结合氮磷比为0.5;流式细胞术显示转染效率为PEI-Fe_3O_4-pDNA+均匀磁场组(77.75%±0.07%)PEI-Fe_3O_4-pDNA+不均匀磁场组(30.65%±0.49%)PEI-Fe_3O_4-pDNA不加磁场组(7.90%±0.56%)(p0.05);PEI-Fe_3O_4磁性纳米颗粒能有效被细胞吞噬,且对细胞形态的影响不大。结果表明,当磁场强度一定时,磁场均匀度越高,磁转染效率越高,单边Halbach磁体与磁转染结合可以作为一种提高转染效率的新手段,也可以进一步应用在基因治疗中。     

磁性钴纳米粒子的制备和应用

介绍了制备磁性钴纳米粒子的方法 ,尤其是介绍了近年发展起来的高温液相法 ,即高温液相还原法 ,金属盐醇解法和金属有机化合物热分解法 ;同时就制备颗粒尺寸小、粒度分布均匀的钴纳米粒子所采用的两种表面活性剂从理论上给予了说明。最后简单介绍了磁性金属钴纳米粒子的主要应用。     

Study of preparation and magnetic properties of silica-coated cobalt ferrite nanocomposites

The structure and the magnetic properties of silica-coated cobalt ferrite nanoparticles (80 wt% CoFe₂O₄), prepared by sol–gel method and submitted to thermal treatments in the range 800–1,000 °C, were investigated through XRD, FT-IR, TEM and VSM. The effects of thermal treatment temperatures on the structure and magnetic properties of nanoparticles were examined. A silica shell thickness of about 5 nm was synthesized on top of cobalt ferrite nanoparticles. The non-crystalline silica confines the growth of cobalt ferrite nanoparticles, i.e., the particle sizes are almost independent of the thermal treatment. Saturation magnetization (Ms) was decreased slightly and coercivity (Hc) was increased, when the non-crystalline silica was coated on the surface of cobalt ferrite nanoparticles.     

便携式原子力显微镜扫描驱动器的设计与实现

设计了一种便携式原子力显微镜压电陶瓷管驱动器,该驱动器使用5～12V宽幅直流电源,产生+215V和±15V的电源供给高压放大模块和信号调理模块,可将输入的-10V～+10V控制信号,放大为-200V～+200V的电压驱动压电陶瓷扫描管,功耗仅为2W左右,体积为150mm×60mm,可以使用电池供电并连续工作7～8h。该驱动器是便携式原子力显微镜的一个重要模块,该模块功能的实现使原子力显微镜在工业现场和野外环境进行测量成为可能。     

Synthesis of Co3 O4 /graphene nanocomposite using paraffin wax for adsorption of methyl violet in water

This study discusses the use of Co₃ O₄ impregnated graphene (CoOIG) as an efficient adsorbent for the removal of methyl violet (MV) dye from wastewater. CoOIG nanocomposites have been prepared by pyrolyzing paraffin wax with cobalt acetate. The synthesised nanocomposite was characterised by X‐ray diffraction, field emission scanning electron microscope, transmission electron microscope, Fourier transform infrared spectroscope, Raman spectroscopy, and Brunauer–Emmett–Teller isotherm studies. The above studies indicate that the composites have cobalt oxide nanoparticles of size 51–58 nm embedded in the graphene nanoparticles. The adsorption studies were conducted with various parameters, pH, temperature and initial dye concentration, adsorbent dosage and contact time by the batch method. The adsorption of MV dye by the adsorbent CoOIG was about 90% initially at 15 min and 98% dye removal at pH 5. The data were fitted in Langmuir, Freundlich, Temkin, and Dubinin–Radushkevich and Sips isotherm models. Various thermodynamic parameters like Gibbs free energy, enthalpy, and entropy of the on‐going adsorption process have also been calculated.Inspec keywords: cobalt compounds, graphene, nanoparticles, nanocomposites, nanofabrication, adsorption, dyes, scanning electron microscopy, field emission electron microscopy, transmission electron microscopy, Raman spectra, Fourier transform infrared spectra, free energy, enthalpy, entropyOther keywords: nanocomposite, paraffin wax, adsorption, methyl violet dye, water, X‐ray diffraction, field emission scanning electron microscopy, transmission electron microscopy, Fourier transform infrared spectroscopy, Raman spectroscopy, Brunauer‐Emmett‐Teller isotherm, cobalt oxide nanoparticles, graphene nanoparticles, thermodynamic parameters, Gibbs free energy, enthalpy, entropy, Co₃ O₄ ‐C     

氧化硅-磁性Fe3O4复合纳米粒子的制备及应用

采用溶胶-凝胶法通过正硅酸四乙酯（TEOS）碱催化水解,在Fe₃O₄纳米粒子表面包裹氧化硅。利用生物倒置显微镜、场发射透射电镜、X射线衍射仪、激光粒度仪、振动样品磁强计对氧化硅/Fe₃O₄复合粒子的外貌、粒径及粒径分布、饱和磁化强度、化学成分进行了表征。结果表明,所制得的复合粒子性能良好,粒径在15 nm左右,饱和磁化强度为109 emu/g。用该磁性纳米复合粒子提取质粒DNA和基因组DNA取得良好的效果,可用于食品中致病菌的分析判定和疾病的基因诊断分析。     

Preparation and characterization of hollow glass microspheres coated by CoFe2O4 nanoparticles using urea as precipitator via coprecipitation method

The composite of hollow glass microspheres coated by CoFe₂O₄ nanoparticles has been successfully prepared using urea as precipitator via coprecipitation method. The resultant composites were characterized by X-ray diffraction, field emission scanning electron microscope and vibrating sample magnetometer. The results showed that the slow decomposition of urea could be beneficial to form uniform and entire cobalt ferrite coating layer on the surface of hollow glass microspheres. The smoothest morphology was obtained for the sample prepared from 0.7 M urea, while the sample prepared from 1.0 M urea had the thickest shell. This indicated that there was a competition between the morphology and thickness of the coated microspheres. A possible formation mechanism of hollow glass microspheres coated with cobalt ferrite was proposed. The magnetic properties of the samples were also investigated.     

Sonochemical Synthesis and Magnetism in Co-doped ZnO Nanoparticles

The understanding and control of ferromagnetism in diluted magnetic semiconducting oxides (DMO) is a special challenge in solid-state physics and materials science due to its impact in magneto-optical devices and spintronics. Several studies and mechanisms have been proposed to explain intrinsic ferromagnetism in DMO compounds since the theoretical prediction of room-temperature ferromagnetism. However, genuine and intrinsic ferromagnetism in 3d-transition metal-doped n-type ZnO semiconductors is still a controversial issue. Furthermore, for DMO nanoparticles, some special physical and chemical effects may also play a role. In this contribution, structural and magnetic properties of sonochemically prepared cobalt-doped ZnO nanoparticles were investigated. A set of ZnO samples was prepared varying cobalt molar concentration and time of ultrasonic exposure. The obtained results showed that single phase samples can be obtained by the sonochemical method. However, cobalt nanoclusters can be detected depending on synthesis conditions. Magnetic measurements indicated a possible ferromagnetic response, associated to defects and cobalt substitutions at the zinc site by cobalt. However, ferromagnetism is depleted at higher magnetic fields. Also, an antiferromagnetic response is detected due to cobalt oxide cluster at high cobalt molar concentrations.