Magneto-structural characterization of different kinds of magnetic nanoparticles

We performed three-dimensional magnetic particle imaging using third-harmonic signal detection. The measurement system consists of three coil types, i.e., an ac excitation coil, a dc gradient coil, and five pickup coils cooled to 77 K. In the experiment, two magnetic nanoparticle samples containing 10 µg (Fe) of magnetic nanoparticles were arranged three-dimensionally with a spacing of 16 mm. An ac excitation field with a strength of 1.6 mT at 3 kHz and a dc gradient field with a field gradient of 0.2 T/m were used. A third-harmonic signal generated from the magnetic nanoparticle samples was detected using the five pickup coils. The noise of the detection system was as low as SB^(1/2) = 7 fT/Hz^(1/2) at a signal frequency of 9 kHz. A magnetic field map generated from the two magnetic nanoparticle samples was obtained by scanning the samples two-dimensionally. Field maps obtained with the five pickup coils were analyzed to reconstruct a three-dimensional distribution image of the magnetic nanoparticle sample. A mathematical technique called the nonnegative least squares method was used for this purpose. We successfully demonstrated three-dimensional magnetic particle imaging. Namely, we reconstructed the three-dimensional positions of the two magnetic nanoparticle samples with good accuracy. Quantities of the two magnetic nanoparticle samples were also estimated reasonably well. These results indicate the feasibility of the present system for three-dimensional magnetic particle imaging.

We studied the AC hysteresis loop and the harmonic spectra of samples containing immobilized magnetic nanoparticles (MNPs) at different values of the excitation field frequency f and amplitude H0. First, we measured the dependences of the coercive field 〈Hc〉 on f and H0. The measured dependences agreed qualitatively with the numerically predicted values. Next, we studied the relationship between 〈Hc〉 and the harmonic spectra, and found strong correlation between 〈Hc〉 and the attenuation rate of these harmonic spectra. We obtained an empirical expression for the harmonic spectra using 〈Hc〉 and a static magnetization curve for the immobilized MNPs. The expression obtained explained the experimental data well. Finally, the harmonic spectra were measured for two MNP samples with different distributions of the magnetic moment m. The MNP sample with the lower m distribution produces richer harmonic spectra for use in magnetic particle imaging.

Magnetic fluid hyperthermia is a promising cancer therapy in which magnetic nanoparticles (MNPs) act as heat sources activated by an external AC magnetic field. The MNPs, located near or inside the tumor, absorb energy from the magnetic field and then heat up the cancerous tissues [1]. However, during a hyperthermia treatment, it is crucial to control the temperature of different tissues: the desired therapeutic effect is not achieved with too low temperature. On the contrary, an excessive temperature increment can produce undesired damage [2]. Nevertheless, the current conventional thermometry in magnetic hyperthermia presents some important technical problems. For example, the widely used optical fiber thermometers only provide the temperature in a discrete. Moreover, surgery is required to locate these probes in the correct place.In this scope, we propose here a non-invasive method to measure the temperature of a MNP sample. The approach is based on the thermal dependence of the high order harmonic phases of the MNP dynamic magnetization. The method is non-invasive and it does not need any additional probe or sensor attached to the MNPs. In addition, this method has the potential to be used to map the spatial distribution of the temperature [3].In the present work, a previously tested lab-made AC magnetometer [4] was used to study the variation with temperature of high order harmonics (3rd , 5th and 7th) from iron oxide MNPs. These MNP samples are identical to those used in a previous work [5]. External AC magnetic fields typical from magnetic hyperthermia were chosen (40-550 kHz). The actual temperature of the sample (30-50 °C) was measured by optical fiber thermometry.I was observed that the high order harmonic phases vary with temperature in an almost linear manner (see figure 1a). Therefore, we propose here the measurement of the harmonic phases as a non-invasive method to obtain the sample temperature. In this scope, the temperature would be obtained via previous calibration of the harmonic phase with temperature. In order to prove this concept an in-vitro experiment has carried out with water dispersed iron oxide MNPs. As it can be observed in figure 2, there is an error less than 0,5 °C.  

In-gel study of the effect of magnetic nanoparticles immobilization on their heating efficiency for application in Magnetic Fluid Hyperthermia

Nickle zinc ferrite (NiZnFe2O4) magnetic nanoparticle (MNPs) has been successfully synthesized using co-precipitation method. NiZnFe2O4 was coated SiO2 (NiZnFe2O4/SiO2) using Stöber method with various concentrations of (5%, 10%, 15%, 20%, 30%, and 50%). MNPs sample has a spinel ferrite phase confirmed by X-ray diffraction (XRD) measurements. The results of the functional group analysis performed using Fourier transform infrared (FTIR) showed an M-O tetrahedral vibrational bond found a wavelength of 347 cm-1. After coated silica, Si-O-Si vibrational bonds appear at wavelengths of 1033.85 cm1. Magnetic properties were measured using vibrating Sample Magnetometer (VSM), the result shows that has maximum saturation magnetization of NiZnFe2O4 22.5 emu.gram-1 and decreased to 16.9 emu.gram-1 after coating. In figure 1 show that the photodegradation activity of MNPs was carried out with a variation of irradiation time. Result of the photodegradation activity of methylene blue shows that NiZnFe2O4/SiO2 are higher than NiZnFe2O4. Sample of NiZnFe2O4/SiO2 has the highest photodegradation rate up to 96%. The existence of SiO2 layer on the surface of bare MNPs increases the surface reactivity of samples.

Amine-functionalized magnetic mesoporous silica nanoparticles for DNA separation

Magnetic nanoparticles (MNPs) have great potential in the drug delivery area. Iron oxide (Fe3O4) MNPs have demonstrated a promising effect due to their ferrimagnetic properties, large surface area, stability, low cost, easy synthesis, and functionalization. Some coating procedures are required to improve stability, biocompatibility, and decrease toxicity for medical applications. Herein, the co-precipitation synthesis of iron oxide MNPs coated with four types of primary surfactants, polyethylene glycol 2000 (PEG 2000), oleic acid (OA), Tween 20 (Tw20), and Tween 80 (Tw80), were investigated. Dynamic light scattering (DLS), ζ-potential, and transmission electron microscopy (TEM) techniques were used for morphology, size, charge, and stability analysis. Methylene blue reactive oxygen species (ROS) detection assay and the toxicity experiment on the lung adenocarcinoma A549 cell line were conducted. Two loading conditions for anticancer drug doxorubicin (DOX) on MNPs were proposed. The first one provides high loading efficiency (~90%) with up to 870 μg/mg (DOX/MNPs) drug capacity. The second is perspective for extremely high capacity 1757 μg/mg with drug wasting (DOX loading efficiency ~24%). For the most perspective MNP_OA and MNP_OA_DOX in cell media, pH 7.4, 5, and 3, the stability experiments are also presented. MNP_OA_DOX shows DOX pH-dependent release in the acidic pH and effective inhibition of A549 cancer cell growth. The IC50 values were calculated as 1.13 ± 0.02 mM in terms of doxorubicin and 0.4 ± 0.03 µg/mL in terms of the amount of the nanoparticles. Considering this, the MNP_OA_DOX nano theranostics agent is a highly potential candidate for cancer treatment.

Magnetic nanoparticles (MNPs) have been popularly used in many fields. Recently, many kinds of MNPs are modified as new absorbents, which have attracted considerable attention and are promising to be applied in waste water. In our previous study, we synthesized two novel MNPs surface-coated with glycine or lysine, which could efficiently remove many anionic and cationic dyes under severe conditions. It should be considered that MNP residues in water may exert some side effects on human health. In the present study, we evaluated the potential nanotoxicity of MNPs in human endothelial cells, macrophages, and rat bone marrow stromal cells. The results showed that the two kinds of nanoparticles were consistently absorbed into the cell cytoplasm. The concentration of MNPs@Gly that could distinctly decrease survival was 15 μg/ml in human umbilical vascular endothelial cells (HUVECs) or bone marrow stromal cells (BMSCs) and 10 μg/ml in macrophages. While the concentration of MNPs@Lys that obviously reduced viability was 15 μg/ml in HUVECs or macrophages and 50 μg/ml in BMSCs. Furthermore, cell nucleus staining and cell integrity assay indicated that the nanoparticles induced cell apoptosis, but not necrosis even at a high concentration. Altogether, these data suggest that the amino acid-coated magnetic nanoparticles exert relatively high cytotoxicity. By contrast, lysine-coated magnetic nanoparticles are more secure than glycine-coated magnetic nanoparticles.

We estimated the effective magnetic anisotropy constant K of magnetic nanoparticles (MNPs) from the temperature dependence of the coercive field Hc of the M–H curve for use in biosensing applications. For this purpose, a previous analytical expression for Hc was extended so that it can be applied to nanoparticles with a size distribution. Using the extended expression for Hc, we estimated the K value of multi-core based MNP sample that consists of crystalline aggregates of elementary particles. We prepared three MNP samples. One is Resovist, in which elementary particles and aggregates are mixed. The Resovist sample was magnetically divided into two fractions called MS1 and MS3, which included mainly aggregates and elementary particles, respectively. We discuss the K value of elementary particles and aggregates from the comparison among the three samples. It is suggested that the K value of the aggregates is much smaller than that of the elementary particles. The temperature dependence of K of the aggregates is also discussed.

Idarubicin-loaded folic acid conjugated magnetic nanoparticles as a targetable drug delivery system for breast cancer

Multi-spectral Magnetic Particle Spectroscopy for the investigation of particle mixtures

A new magnetic nanoparticle detection system by using a fundamental mode orthogonal fluxgate (FM-OFG) gradiometer and ac magnetizing coil has been developed. The FM-OFG gradiometer has an active canceling coil on each of its sensor heads against the common magnetic field input to avoid the saturation of the amorphous wire core by a strong ac magnetic field. In addition, the ac magnetizing coil has an adjusting capability to make ac magnetic field strength affecting each of the gradiometer heads equal, which allows us to use a high gain amplifier at the latter stage. Two types of the gradiometer are tested: one is parallel configuration in which two sensor heads are placed in parallel side by side, the other is axial configuration in which two sensor heads are placed axially. Detectable distance was investigated using a 5μL (≈100μg in Fe atomic amount) magnetic nanoparticle sample. The maximum detectable distance for the parallel gradiometer is 17 mm, and that for the axial one is 18 mm.

Folic acid-conjugated Fe3O4 magnetic nanoparticles for hyperthermia and MRI in vitro and in vivo

Magnetic nanoparticles (NPs) have attracted great attention owing to their applications in the biomedical field. In the present work, maghemite (γFe2O3) NPs of 6.5 nm were prepared using a sonochemical method and used to prepare magnetic beads through silanization with 3-aminopropyltrimethoxysilane (APTS). Subsequently, amino groups in the resulting APTS-γFe2O3 beads were converted to carboxylic acid (CARB-γFe2O3) through the succinic anhydride reaction, as confirmed by transmission electron microscopy (TEM), Fourier transform infrared spectroscopy and dynamic light scattering (DLS) measurements. The size of these beads was measured as 12 nm and their hydrodynamic diameter as 490 nm, using TEM analysis and DLS, respectively. The CARB-γFe2O3 beads were further functionalized by immobilizing rabbit antibodies on their surfaces; the immobilization was confirmed by flow cytometry and ionic strength. The samples were further characterized by Mössbauer spectroscopy and DC magnetization measurements. Studies on magnetic relaxivities showed that magnetic beads present great potential for application in MR imaging.

ABSTRACTIn this study, first, magnetic nanoparticles (MNP) were synthesized using a coprecipitation method and the synthesized particles were characterized using Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), dynamic light scattering (DLS), and vibrating sample magnetometry (VSM). According to DLS and VSM analyses results, it was seen that the size of the MNP was smaller than 10 nm and they exhibited superparamagnetic properties, respectively. Then, magnetic Fe3O4-chitosan micro/nanoparticles were synthesized using a suspension cross-linking method in the presence of the MNP. Fe3O4-chitosan microparticles (Fe3O4-CMs) and Fe3O4-chitosan nanoparticles (Fe3O4-CNs), which have different structural, morphological, and magnetic properties, were obtained. All of the particles were characterized using transmission electron microscopy (TEM), FTIR, TGA, DLS, and VSM. In the second part of the study, the dye adsorption properties of the two different adsorbents from aqueous solution were investigated. For these purposes, Bromothymol Blue (BB) was used as a dye and the parameters affecting adsorption of BB (contact time, initial dye concentration, temperature and pH) were investigated. When the optimum adsorption conditions were provided for each adsorbent, the adsorption capacities of Fe3O4-CNs and Fe3O4-CMs were 82.2 and 193.3 mg/g, respectively.