壳聚糖修饰氧化铁磁性纳米颗粒的制备和性能研究

通过共沉淀法制备氧化铁磁性纳米颗粒,用壳聚糖对其表面进行修饰得到样品(CS@MNPs);表征其形貌结构、尺寸、表面基团、表面电荷、磁学性质和在不同介质中的稳定性等。实验结果表明,CS@MNPs具有典型的立方反尖晶石晶体结构;粒径为16.5nm;在生理(pH值7.4)条件下拥有较高的正电荷(10mV);呈现超顺磁性,对驰豫时间T1、T2,尤其是T2*具有很强的响应;在双蒸馏水和含10%新生牛血清的RPMI 1640培养液中具有良好的稳定性,具有作为磁共振造影剂的潜力。     

Synthesis and characterization of silica-embedded iron oxide nanoparticles for magnetic resonance imaging

In this communication, a conceptually new approach to the delivery of magnetic resonance imaging (MRI) contrast agents is presented. Our experiments demonstrate the feasibility of using silica-embedded iron oxide nanoparticles as contrast agents in magnetic resonance imaging, where a reduction in signal intensity (increased contrast) in the T2-weighted images is observed. The surface of these particles can be chemically modified by attachment of polyethylene glycol molecules, which are found to reduce nonspecific protein binding. The design of the nanoparticle is universal and flexible and allows for facile addition or interchange of its active components (i.e., MRI contrast agents and targeting moiety) with photodynamic dyes.     

One-pot size and shape controlled synthesis of DMSO capped iron oxide nanoparticles

We report here the capping of iron oxide nanoparticles with dimethyl sulfoxide (DMSO) to make chloroform soluble iron oxide nanoparticles. Size and shape of the capped iron oxide nanoparticles are well controlled by simply varying the reaction parameters. The synthesized nanocrystallites were characterized by thermal analysis (TG-DTA), powder X-ray diffraction (XRD), transmission electron microscopy (TEM) for evaluating phase, structure and morphology. ¹H NMR spectra of the synthesized samples confirm DMSO, and the capping of DMSO on the ferrite samples. Shift of the S=O stretching frequency in Fourier transformed infra-red (FTIR) spectra indicates that the bonding between DMSO and ferrite is through an oxygen moiety. The magnetic measurements of all the synthesized samples were investigated with a SQUID magnetometer which shows that the magnetic properties are strongly dependent on the size as well as shape of the iron oxide.     

Carbon microspheres with embedded magnetic iron oxide nanoparticles

Narrow-size disperse porous carbon microspheres with embedded magnetite nanoparticles were prepared by annealing Fe(III)-containing microspheres composed of a copolymer of acrylic acid and divinylbenzene at 800 °C under inert atmosphere. The Fe(III)-containing microspheres were prepared by uptake of Fe²⁺ ions through ion exchange process by poly(acrylic acid-divinylbenzene) microspheres that were prepared by distillation-precipitation polymerization, followed by annealing at 250 °C at ambient atmosphere. The carbonization of the microspheres created micropores with a maximum pore diameter of about 0.38 nm and a BET surface area of ~ 200 m²/g. The saturation magnetization of the magnetic carbon microspheres was 31.5 emu/g with a low remnant magnetization and coercivity.     

Synthesis and characterization of multifunctional iron oxide nanoparticles

In order to get high water solubility, monodisperse, superparamagnetic nanoparticles, poly (acrylic acid) was employed to modify Fe3O4 by a high-temperature solution-phase hydrolysis approach. Then, folic acid (FA) and fluorescein isothiocyanate were successively conjugated with prepared magnetic nanoparticles (MNPs). The functional MNPs were characterized by X-ray diffraction (XRD), dynamic light scattering (DLS), transmission electron microscope (TEM), inductively coupled plasma-atomic emission spectrometer (ICP-AES), and vibrating sample magnetometer (VSM), respectively. The toxicity of the materials was evaluated by selecting NIH/3T3 fibroblast cells and no toxic effect was observed. The fluorescent imaging and targeting property of the MNPs were also realized in vitro and in vivo experiments by confocal laser scanning microscopy (CLSM) and Kodak In-Vivo FX Professional Imaging System, respectively. The results indicated that the final products exhibited interesting magnetic, optical and targeting properties for further potential applications in biological and biomedical fields.     

A novel approach for transferring oleic acid capped iron oxide nanoparticles to water phase

A novel and simple method was described to transfer oleic acid stabilized iron oxide nanoparticles from organic solutions to water. The oxidation of OA by sodium periodate in mixed solvents formed a carboxyl group or vicinal diol to make the hydrophobic groups to hydrophilic groups on the surface of the nanoparticles. The characterization of nanoparticles indicated that the phase transfer based on the oxidation of OA was successful performed without change in the size and shape of the iron oxide nanoparticles. The hydrophilic groups on the iron oxide surface stabilized the nanoparticles in aqueous solution and the oxidized nanoparticles can be applied to bimolecular immobilization.     

Carboxymethylated dextran-coated magnetic iron oxide nanoparticles for regenerable bioseparation

Carboxymethylated dextran (CMD)-coated magnetic iron oxide nanoparticles (MNPs) were synthesized using a co-precipitation method. Compared to neutral dextran coated MNPs, the CMD coating provides good dispersity and colloidal stability to the CMD-MNPs. In particular, the carboxyl groups on the CMD can be readily activated for covalent attachment of antibody molecules. The superparamagnetic property of the antibody-covered CMD-MNPs enables the captured antigen to be separated from the sample solution and CMD coating significantly reduces the nonspecific binding of the nanoparticles. Regeneration of the anti-BSA antibody-covered CMD-MNPs with NaOH does not significantly decrease the antibody activity, and the repeated magnetic separation and washing steps cause only small loss of the starting materials. The method was found to be highly reproducible (RSDs for BSA adsorption and desorption are between 0.78% and 5.1%). The anti-BSA antibody-covered CMD-MNPs possess good selectivity and are able to capture protein antigens from real samples.     

Facile synthesis of magnetic iron oxide nanoparticles and their characterization

Magnetic iron oxide nanoparticles are synthesized by suitable modification of the standard synthetic procedure without use of inert atmosphere and at room temperature. The facile synthesis procedure can be easily scaled up and is of important from industrial point of view for the commercial large scale production of magnetic iron oxide nanoparticles. The synthesized nanoparticles were characterized by thermal, dynamic light scattering, scanning electron microscopy and transmission electron microscopy analyses.     

Synthesis of monodisperse iron oxide and iron/iron oxide core/shell nanoparticles via iron-oleylamine complex

Monodisperse magnetic nanoparticles are of great scientific and technical interests. This paper reports a single-step synthesis of monodisperse magnetite nanoparticles with particle size of 8 nm. Iron/maghaemite core/shell nanoparticles with particle size of 11 nm were obtained by reducing the concentration of oleylamine. TEM and in-situ FTIR results suggested that iron-oleylamine intermediate was generated in-situ and decomposed at higher temperature. Oleylamine was also found on the surface of nanoparticles, indicating its role as capping agent which provided steric protection of as-synthesized nanoparticles from agglomeration. Both magnetite and iron/maghaemite core/shell nanoparticles were superparamagnetic at room temperature with a blocking temperature at 80 K and 67 K, respectively.     

Synthesis and characterization of iron oxide nanoparticles dispersed in mesoporous aluminum oxide or silicon oxide

Iron oxide nanoparticles dispersed in aluminum (Al) or silicon (Si) oxides were prepared via a polymeric precursor derived from the Pechini method. The samples were characterized by thermogravimetric analysis, Fourier-transform infrared spectroscopy, X-ray diffraction, N₂ adsorption/desorption isotherms (Brunauer–Emmett–Teller, BET), M?ssbauer spectroscopy, and vibrating sample magnetometry (VSM). BET analysis shows that the samples are mesoporous materials and have a high surface area. The size of the Fe₂O₃ nanoparticles in Al₂O₃ is smaller than that in SiO₂. M?ssbauer spectra of the samples show that the Fe₂O₃ nanoparticles in Al₂O₃ are non-magnetic at room temperature but magnetic below 50 K. The FeSi samples are magnetic at both room and low temperatures. The magnetic measurements with VSM confirmed this point.     

Bioactivity of gelatin coated magnetic iron oxide nanoparticles: in vitro evaluation

Current research explores formation of bone like apatite on gelatin coated magnetic iron oxide nanoparticles (GIOPs) to evaluate the bioactivity of the material. The GIOPs were soaked in simulated body fluid (SBF) and the apatite formation on the surface was investigated in regular interval of time. Fourier transform-infrared (FT-IR) and x-ray diffraction spectroscopic (XRD) analyses were done to investigate the chemical changes and field emission-scanning electron microscopic (FE-SEM) analysis was done to investigate the morphological changes occurring on the surface of the GIOPs after soaking in different time intervals. The kinetic studies of the apatite growth in SBF suggest that initially calcium and phosphorous ions were deposited to the surface of the GIOPs from the SBF leading to formation of amorphous Ca/P particles. Later, after 9 days of the incubation the amorphous particles were fused to form needle and blade like crystalline structures of bone like apatite.     

Uptake of dimercaptosuccinate-coated magnetic iron oxide nanoparticles by cultured brain astrocytes

Magnetic iron oxide nanoparticles (Fe-NP) are currently considered for various diagnostic and therapeutic applications in the brain. However, little is known on the accumulation and biocompatibility of such particles in brain cells. We have synthesized and characterized dimercaptosuccinic acid (DMSA) coated Fe-NP and have investigated their uptake by cultured brain astrocytes. DMSA-coated Fe-NP that were dispersed in physiological medium had an average hydrodynamic diameter of about 60 nm. Incubation of cultured astrocytes with these Fe-NP caused a time- and concentration-dependent accumulation of cellular iron, but did not lead within 6 h to any cell toxicity. After 4 h of incubation with 100-4000 μM iron supplied as Fe-NP, the cellular iron content reached levels between 200 and 2000 nmol mg?1 protein. The cellular iron content after exposure of astrocytes to Fe-NP at 4?°C was drastically lowered compared to cells that had been incubated at 37?°C. Electron microscopy revealed the presence of Fe-NP-containing vesicles in cells that were incubated with Fe-NP at 37?°C, but not in cells exposed to the nanoparticles at 4?°C. These data demonstrate that cultured astrocytes efficiently take up DMSA-coated Fe-NP in a process that appears to be saturable and strongly depends on the incubation temperature.     

M2 macrophage-targeted iron oxide nanoparticles for magnetic resonance image-guided magnetic hyperthermia therapy

Tumor-associated macrophages (TAMs) play an important role in tumor development and progression.In particular,M2 TAMs can promote tumor growth by facilitating tumor progression and malignant behav-iors.Selectively targeted elimination of M2 TAMs to inhibit tumor progression is of great significance for cancer treatment.Iron oxide nanoparticles based magnetic hyperthermia therapy (MHT) is a classical approach to destroy tumor tissue with deep penetration depth.In this study,we developed a typical M2 macrophage-targeted peptide (M2pep) functionalized superparamagnetic iron oxide nanoparticle(SPIO) for magnetic resonance imaging (MRI)-guided MHT in an orthotopic breast cancer mouse model,The obtained multifunctional SPIO-M2pep with a hydrodynamic diameter of 20 nm showed efficient targeting capability,high transverse relaxivity (149 mM-1 s-1) and satisfactory magnetic hyperthermia performance in vitro.In vivo studies demonstrated that the SPIO-M2pep based MRI can monitor the distri-bution of nanoparticles in tumor and indicate the suitable timing for MHT.The M2 macrophage-targeted MHT significantly reduced the tumor volume and the population of pro-tumoral M2 TAMs in tumor.In addition,the SPIO-M2pep based MHT can remodel the tumor immune microenvironment (TIME).The multifunctional SPIO-M2pep with M2 macrophage-targeting ability,high magnetic hyperthermia effi-ciency,MR imaging capability and effective role in remodeling the TIME hold great potential to improve clinical cancer therapy outcomes.     

Fabrication of iron oxide nanoparticles: magnetic and electrochemical sensing property

In this paper, we report a simple synthesis of Fe₂O₃ nanoparticles using hydrothermal method. The formation of the sample was confirmed by X-ray diffraction analysis, X-ray photoelectron spectroscopy, Fourier transformed infrared spectroscopy, Raman spectroscopy and UV–Visible absorption spectroscopy. The average crystallite size of the synthesized Fe₂O₃ nanoparticles was estimated to be 61 nm and the particles were of good crystalline nature. Field emission-scanning electron microscopy study of the sample revealed that the Fe₂O₃ powder has rod-like morphology which is composed of nanoparticles. The vibrating sample magnetometer measurement shows that the nanoparticles possess ferromagnetic property. The synthesized Fe₂O₃ nanoparticles were used to modify glassy carbon electrode (Fe₂O₃/GCE) and the modified electrode was used to detect pyrocatechol (PC) in a pH 7.4 phosphate buffer solutions by cyclic voltammetry and chronoamperometry. At the Fe₂O₃/GCE, PC is oxidized at less positive potential with larger current response than the bare GCE. The proposed sensor exhibits great potential in the field of electrochemical sensing of PC.     

Structure and magnetic properties of iron based nanoparticles with oxide shells

Oxide-coated iron nanoparticles with average dimensions from 6 to 75 nm have been synthesized by chemical vapor condensation. The structure of particles and their size distribution have been determined. These data are used to interpret the results of measurements of the magnetic hysteresis characteristics.     

Magnetoacoustic imaging of magnetic iron oxide nanoparticles embedded in biological tissues with microsecond magnetic stimulation

We present an experimental study on magnetoacoustic imaging of superparamagnetic iron oxide (SPIO) nanoparticles embedded in biological tissues. In experiments, a large-current-carrying coil is used to deliver microsecond pulsed magnetic stimulation to samples. The ultrasound signals induced by magnetic forces on SPIO nanoparticles are measured by a rotating transducer. The distribution of nanoparticles is reconstructed by a back-projection imaging algorithm. The results demonstrated the feasibility to obtain cross-sectional image of magnetic nanoparticle targets with faithful dimensional and positional information, which suggests a promising tool for tomographic reconstruction of magnetic nanoparticle-labeled diseased tissues (e.g., cancerous tumor) in molecular or clinic imaging.     

Synthesis and characterization of L-histidine capped silver nanoparticles

L-histidine capped Ag nanoparticles have been synthesized by a hydrothermal method. Spherical Ag nanoparticles with average diameter ranging from 9 to 21 nm can be obtained by tuning the reaction pH and the reactant ratio. The topography, surface and internal structures of the histidine capped Ag nanoparticles have been characterized by transmission electron microscopy (TEM), atomic force microscopy (AFM), dynamic light scattering, X-ray photoelectron spectroscopy (XPS), X-ray Diffraction (XRD), Raman spectroscopy and UV–vis absorption spectroscopy. Surface enhanced Raman scattering (SERS) results revealed that the Ag colloid in present study have a structure that the imidazole moiety of histidine is bound on the Ag surface and COO^? group is exposed outward. The as-synthesized Ag colloidal solution was very stable and can be stored at room temperature at least one month. In addition, it was found that the solution color of Ag colloid can change from yellow to reddish-brown by addition of the NiCl₂ solution, which may have potential application for Ni²⁺ detection.     

Synthesis of graphene soluble in organic solvents by simultaneous ether-functionalization with octadecane groups and reduction

Octadecane-functionalized graphene (OD-G) soluble in organic solvents was produced by combining the Hummers process for graphite oxidation and a simultaneous ether-functionalization and reduction approach with 1-bromooctadecane in pyridine and dimethylformamide (DMF). The exfoliated OD-Gs were testified to be monolayer sheets by transmission electron microscope (TEM) and atomic force microscopy (AFM). The functionalization with octadecane (OD) groups and the effective deoxygenation of graphene oxide (GO) were confirmed by Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD) and thermogravimetric analysis (TGA). It is proved that the effective reduction and functionalization of GO could be simultaneously completed during the refluxing process. The functionalization with OD groups can effectively prevent the aggregation of GO during the reduction.     

Multifunctional iron and iron oxide nanoparticles in silica

Iron and iron oxide nanoparticles in silica layers deposited by sol–gel techniques on Si wafers were formed and studied. It was shown that multifunctional nanoparticles of different iron oxides possessing various physical properties can be fabricated by means of post-growth annealing of (SiO₂:Fe)/SiO₂/Si samples in various atmospheres. The hematite, maghemite, and iron nanoparticles were found to be dominant upon annealing the samples in air, argon, and hydrogen atmosphere, respectively. The physical properties of produced hybrid structures were studied by Raman and FT-IR spectroscopy, spectroscopic ellipsometry, AFM, and magnetic measurements. The sol–gel technique with subsequent annealing procedure is demonstrated to be an effective method for the formation of multifunctional hybrid structures composed of iron or iron oxide nanoparticles in silica matrix.     

Synthesis of highly magnetic graphite-encapsulated FeCo nanoparticles using a hydrothermal process

The graphite encapsulation of metal alloy magnetic nanoparticles has attracted attention for biological applications because of the high magnetization of the encapsulated particles. However, most of the synthetic methods have limitations in terms of scalability and economics because of the demanding synthetic conditions and low yields. Here, we show that well controlled graphite-encapsulated FeCo core-shell nanoparticles can be synthesized by a hydrothermal method, simply by mixing Fe/Co with sucrose as a carbon source. Various Fe/Co metal ratios were used to determine the compositional dependence of the saturation magnetization and relaxivity coefficient. Transmission electron microscopy indicated that the particle sizes were 7 nm. In order to test the capability of graphite-encapsulated FeCo nanoparticles as magnetic resonance imaging (MRI) contrast agents, these nanoparticles were solubilized in water by the nonspecific physical adsorption of sodium dodecylbenzene sulfonate.