Magnetic fluid poly(ethylene glycol) with moderate anticancer activity

Poly(ethylene glycol) (PEG)-containing magnetic fluids - magnetite (Fe₃O₄) stabilized by sodium oleate - were prepared. Magnetic measurements confirmed superparamagnetic behaviour at room temperature. The structure of that kind of magnetic fluid was characterized using different techniques, including electron microscopy, photon cross correlation spectroscopy and small-angle neutron scattering, while the adsorption of PEG on magnetic particles was analyzed by differential scanning calorimetry and Fourier transform infrared spectroscopy. From the in vitro toxicity tests it was found that a magnetic fluid containing PEG (MFPEG) partially inhibited the growth of cancerous B16 cells at the highest tested dose (2.1 mg/ml of Fe₃O₄ in MFPEG).     

Synthesis protocol influence on aqueous magnetic fluid properties

Magnetic colloids containing superparamagnetic Fe₃O₄ nanoparticles have been prepared by co-precipitation method. Three samples of citric acid coated magnetic colloids containing magnetic nanoparticles (ultra-fine particles of Fe₃O₄) have been obtained following three different preparation protocols. Physical tests have been performed on these samples of the magnetic colloids prepared by us (consisting mainly of Fe₃O₄ ultra-fine particles stabilized with citric acid (C₆H₈O₇) and immersed in water), in order to reveal their microstructural and rheological features. Transmission electron microscopy (TEM) and magnetic measurements were the investigation methods used for the assessing of the magnetic nanoparticles size. The dimensional distribution of the ferrophase physical diameter was comparatively presented using the box-plot statistical method. Infrared absorption spectra have been recorded aiming to get some information on the magnetic fluid composition.     

Microwave synthesis of magnetic Fe3O4 nanoparticles used as a precursor of nanocomposites and ferrofluids

Methods to synthesize magnetic Fe₃O₄ nanoparticles and to modify the surface of particles are presented in the present investigation. Fe₃O₄ magnetic nanoparticles were prepared by the co-precipitation of Fe³⁺ and Fe²⁺, NH₃·H₂O was used as the precipitating agent to adjust the pH value, and the aging of Fe₃O₄ magnetic nanoparticles was accelerated by microwave (MW) irradiation. The obtained Fe₃O₄ magnetic nanoparticles were characterized by Fourier transform infrared spectroscopy (FT-IR), transmission electron microscopy (TEM), X-ray powder diffraction (XRD) and vibrating sample magnetometer (VSM). The average size of Fe₃O₄ crystallites was found to be around 8–9 nm. Thereafter, the surface of Fe₃O₄ magnetic nanoparticles was modified by stearic acid. The resultant sample was characterized by FT-IR, scanning electron microscopy (SEM), XRD, lipophilic degree (LD) and sedimentation test. The FT-IR results indicated that a covalent bond was formed by chemical reaction between the hydroxyl groups on the surface of Fe₃O₄ nanoparticles and carboxyl groups of stearic acid, which changed the polarity of Fe₃O₄ nanoparticles. The dispersion of Fe₃O₄ in organic solvent was greatly improved. Effects of reaction time, reaction temperature and concentration of stearic acid on particle surface modification were investigated. In addition, Fe₃O₄/polystyrene (PS) nanocomposite was synthesized by adding surface modified Fe₃O₄ magnetic nanoparticles into styrene monomer, followed by the radical polymerization. The obtained nanocomposite was tested by thermogravimetry (TG), differential scanning calorimetry (DSC) and XRD. Results revealed that the thermal stability of PS was not significantly changed after adding Fe₃O₄ nanoparticles. The Fe₃O₄ magnetic fluid was characterized using UV–vis spectrophotometer, Gouy magnetic balance and laser particle-size analyzer. The testing results showed that the magnetic fluid had excellent stability, and had susceptibility of 4.46×10⁻⁸ and saturated magnetization of 6.56 emu/g. In addition, the mean size d (0.99) of magnetic Fe₃O₄ nanoparticles in the fluid was 36.19 nm.     

Preparation and characterization of silica-coated Fe3O4 nanoparticles used as precursor of ferrofluids

Fe₃O₄ magnetic nanoparticles (MNPs) were synthesized by the co-precipitation of Fe³⁺ and Fe²⁺ with ammonium hydroxide. The sodium citrate-modified Fe₃O₄ MNPs were prepared under Ar protection and were characterized by Fourier transform infrared spectroscopy (FT-IR), transmission electron microscopy (TEM), X-ray powder diffraction (XRD) and vibrating sample magnetometer (VSM). To improve the oxidation resistance of Fe₃O₄ MNPs, a silica layer was coated onto the modified and unmodified MNPs by the hydrolysis of tetraethoxysilane (TEOS) at 50 °C and pH 9. Afterwards, the silica-coated Fe₃O₄ core/shell MNPs were modified by oleic acid (OA) and were tested by IR and VSM. IR results revealed that the OA was successfully grafted onto the silica shell. The Fe₃O₄/SiO₂ core/shell MNPs modified by OA were used to prepare water-based ferrofluids (FFs) using PEG as the second layer of surfactants. The properties of FFs were characterized using a UV-vis spectrophotometer, a Gouy magnetic balance, a laser particle size analyzer and a Brookfield LVDV-III+ rheometer.     

Synthesis and characterization of functionalized core-shell γFe2O3-SiO2 nanoparticles

Amino and/or polyethyleneglycol (PEG) functionalized core-shell γFe₂O₃-SiO₂ magnetic nanoparticles were synthesized and characterized. Amino-PEG-functionalized core-shell nanoparticles have calibrated sizes and a good colloidal stability. These bi-functionalized core-shell nanoparticles are potentially useful as biocompatible particles for magnetically targeted chemotherapy.     

Magnetic field synthesis of Fe3O4 nanoparticles used as a precursor of ferrofluids

Methods to synthesize magnetic Fe₃O₄ nanoparticles and to modify the nanoparticle surface are presented in this paper. In these methods, Fe₃O₄ nanoparticles were prepared by co-precipitation, and the aging of nanoparticles was improved by applied magnetic field. The obtained nanoparticles were characterized by Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), X-ray powder diffraction (XRD), and vibrating sample magnetometer (VSM). Thereafter, to enhance the compatibility between nanoparticles and water, an effective surface modification method was developed by grafting acrylic acid onto the nanoparticle surface. FT-IR, XRD, transmission electron microscopy (TEM), and thermogravimetry (TG) were used to characterize the resultant sample. The testing results indicated that the polyacrylic acid chains have been covalently bonded to the surface of magnetic Fe₃O₄ nanoparticles. The effects of initiator dosage, monomer concentration, and reaction temperature on the characteristics of surface-modified Fe₃O₄ nanoparticles were investigated. Moreover, the Fe₃O₄-g-PAA hybrid nanoparticles were dispersed in water to form ferrofluids (FFs). The obtained FFs were characterized by UV–vis spectrophotometer, Gouy magnetic balance and laser particle-size analyzer. The testing results showed that the high-concentration FF had excellent stability, with high susceptibility and high saturation magnetization. The rheological properties of the FFs were also investigated using a rotating rheometer.     

Highly Ligand‐Directed and Size‐Dependent Photothermal Properties of Magnetite Particles

The development of cancer photothermal therapies, many of which rely on photothermal agents, has received significant attention in recent years. In this work, various ligands‐stabilized magnetite (Fe₃O₄) particles are fabricated and utilized as a photothermal agents for in vivo tumor‐imaging‐guided photothermal therapy. Fe₃O₄ particles stabilized by macromolecular ligands as, e.g. polyethylene glycol (PEG), exhibit a superior and more stable photothermal effect compared to Fe₃O₄ particles stabilized by small molecules like citrate, due to their stronger ability of antioxidation. In addition, the photothermal effect of Fe₃O₄ particles is revealed to increase with size, which is attributed to the redshift of Vis‐NIR spectra. Fe₃O₄ particles injected intravenously into mice can be accumulated in the tumor by the application of an external magnetic field, as revealed by magnetic resonance imaging. In vivo photothermal therapy test of PEG‐stabilized Fe₃O₄ further achieves better tumor ablation effect. Overall, this study demonstrates efficient imaging‐guided photothermal therapy of cancer that is based on Fe₃O₄ particles of optimized size and with optimized ligands. It is expected that the ligand‐directed and size‐dependent photothermal effect will provide more approaches in the design of novel materials.     

Synthesis of Fe3O4 magnetic fluid used for magnetic resonance imaging and hyperthermia

Fe₃O₄ magnetic nanoparticles were prepared by co-precipitation from FeSO₄·7H₂O and FeCl₃·6H₂O aqueous solutions using NaOH as precipitating reagent. The nanoparticles have an average size of 12 nm and exhibit superparamagnetism at room temperature. The nanoparticles were used to prepare a water-based magnetic fluid using oleic acid and Tween 80 as surfactants. The stability and magnetic properties of the magnetic fluid were characterized by Gouy magnetic balance. The experimental results imply that the hydrophilic block of Tween 80 can make the Fe₃O₄ nanoparticles suspending in water stable even after dilution and autoclaving. The magnetic fluid demonstrates excellent stability and fast magneto-temperature response, which can be used both in magnetic resonance imaging and magnetic fluid hyperthermia.     

Fabrication, characterization and measurement of thermal conductivity of Fe3O4 nanofluids

Magnetite Fe₃O₄ nanoparticles were synthesized by a co-precipitation method at different pH values. The products were characterized by X-ray diffraction, Fourier transform infrared spectroscopy, and transmission electronic microscopy. Their magnetic properties were evaluated on a vibrating sample magnetometer. The results show that the shape of the particles is cubic and they are superparamagnetic at room temperature. Magnetic nanofluids were prepared by dispersing the Fe₃O₄ nanoparticles in water as a base fluid in the presence of tetramethyl ammonium hydroxide as a dispersant. The thermal conductivity of the nanofluids was measured as a function of volume fraction and temperature. The results show that the thermal conductivity ratio of the nanofluids increases with increase in temperature and volume fraction. The highest enhancement of thermal conductivity was 11.5% in the nanofluid of 3 vol% of nanoparticles at 40 °C. The experimental results were also compared with the theoretical models.     

Synthesis and properties of hybrid hydroxyapatite–ferrite (Fe<Subscript>3</Subscript>O<Subscript>4</Subscript>) particles for hyperthermia applications

Hybrid ceramics consisting of hydroxyapatite Ca₁₀(PO₄)₆(OH)₂ and ferrite Fe₃O₄ were synthesized using a two-stage procedure. The first stage included the synthesis of Fe₃O₄ ferrite particles by co-precipitation and the synthesis of hydroxyapatite. In the second stage, the magnetic hybrid hydroxyapatite–ferrite bioceramics were synthesized by a thorough mixing of the obtained powders of carbonated hydroxyapatite and Fe₃O₄ ferrite taken in a certain proportion, pressing into tablets, and annealing in a carbon dioxide atmosphere for 30 min at a temperature of 1200°C. The properties of the components and hybrid particles were investigated using X-ray diffraction, scanning electron microscopy, transmission electron microscopy, and Mössbauer spectroscopy. The saturation magnetization of the hybrid ceramic composite containing 20 wt % Fe₃O₄ was found to be 12 emu/g. The hybrid hydroxyapatite (Ca₁₀(PO₄)₆(OH)₂)–ferrite Fe₃O₄ ceramics, which are promising for the use in magnetotransport and hyperthermia treatment, were synthesized and investigated for the first time.     

Magnetic and Mössbauer studies of fucan-coated magnetite nanoparticles for application on antitumoral activity

Fucan-coated magnetite (Fe₃O₄) nanoparticles were synthesized by the co-precipitation method and studied by Mössbauer spectroscopy and magnetic measurements. The sizes of the nanoparticles were 8–9 nm. Magnetization measurements and Mössbauer spectroscopy at 300 K revealed superparamagnetic behavior. The magnetic moment of the Fe₃O₄ is partly screened by the Fucan coating aggregation. When the magnetite nanoparticles are capped with oleic acid or fucan, reduced particle-particle interaction is observed by Mössbauer and TEM studies. The antitumoral activity of the fucan-coated nanoparticles were tested in Sarcoma 180, showing an effective reduction of the tumor size.     

In situ growth of sol–gel-derived nano-VO2 film and its phase transition characteristics

Fe₃O₄/C nanocomposites have been prepared by one-pot PEG-assisted co-precipitation method. The structure and morphology of the as-prepared materials were analyzed by X-ray diffraction and transmission electron microscopy. The results showed that Fe₃O₄/C nanocomposites were well crystallized. Carbon nanoparticles dispersed among Fe₃O₄ particles forming a carbon layer, which prevent Fe₃O₄ particles from contacting each other. Electrochemical performance tests showed that Fe₃O₄/C nanocomposites keep at a high discharge capacity of 902.4 mAh g^?1 at 1 C after 110 cycles. Furthermore, the samples showed much improved rate capability and better cycle stability compared with pure Fe₃O₄. The excellent electrochemical performance of Fe₃O₄/C nanocomposites can be attributed to unique nanostructure and existence of amorphous carbon in the composites. The existence of the amorphous carbon not only enhanced electric conductivity, but also buffered volume variation of Fe₃O₄/C nanocomposites during charge/discharge process.     

Preparation of superparamagnetic Fe3O4/PMMA nano composites and their magnetorheological characteristics

Fe₃O₄/PMMA composite particles were fabricated by a simple one-pot hydrothermal method. The magnetic measurement showed that the composite particles displayed a higher saturated magnetization and superparamagnetic property. The rheological properties of the magnetorheological fluids (MRFs) based on Fe₃O₄/PMMA particles were measured on a rotational rheometer with a magnetic field generator. It was found that the MRFs exhibited better MR effect and sendimentary stability than the similar materials.     

Preparation of Fe3O4/polystyrene composite particles from monolayer oleic acid modified Fe3O4 nanoparticles via miniemulsion polymerization

Fe₃O₄/polystyrene composite particles were prepared from oleic acid (OA) modified Fe₃O₄ nanoparticles via miniemulsion polymerization. It was concluded that the surface properties of OA modified magnetite nanoparticles have a great effect on preparation of the composite particles. When Fe₃O₄ nanoparticles coated by multilayer of OA was employed, there were large amounts of free polystyrene particles in the product. Fe₃O₄/polystyrene composite particles with defined structure and different magnetite content can be readily prepared from monolayer OA modified Fe₃O₄ nanoparticles. It was concluded that surface of the monolayer OA modified Fe₃O₄ nanoparticles is more hydrophobic than that of the multilayer coated ones, thus improving the dispersibility of the Fe₃O₄ nanoparticles in styrene monomer and allowing preparation of the Fe₃O₄/polystyrene composite particles with defined structure and controllable magnetite content.     

Synthesis of Fe3O4 nanoparticles without inert gas protection used as precursors of magnetic fluids

Fe₃O₄ nanoparticles were hydrothermally synthesized under continuous microwave irradiation from FeCl₃·6H₂O and FeSO₄·7H₂O aqueous solutions, using NH₄OH as precipitating reagent and N₂H₄·H₂O as oxidation-resistant reagent. The results of X-ray powder diffraction (XRD), FT–IR spectroscopy and scanning electron microscopy (SEM) measurements showed that the synthesized magnetite (Fe₃O₄) nanoparticles had an average diameter of 10 nm. The magnetic properties of the Fe₃O₄ nanoparticles were measured using a vibrating sample magnetometer (VSM), indicating that the nanoparticles possessed high saturation magnetization at room temperature. The Fe₃O₄ nanoparticles were used to prepare magnetic fluids (MFs) based on water, and the properties of the MFs were characterized by a Gouy magnetic balance, a capillary rheometer and a rotating rheometer, respectively.     

Studies on polyethylene glycol coating on NiFe2O4 nanoparticles for biomedical applications

The NiFe₂O₄ nanoparticles were prepared by the combustion method and these nanoparticles were successfully coated with polyethylene glycol (PEG) for the possible biomedical applications such as magnetic resonance imaging, drug delivery, tissue repair, magnetic fluid hyperthermia etc. The structural and magnetic characterizations of NiFe₂O₄ nanoparticles were carried out by x-ray diffraction and vibrating sample magnetometry techniques, respectively. The morphology of the uncoated and coated nanoparticles was studied by scanning electron microscopy. The existence of PEG layer on NiFe₂O₄ nanoparticles was confirmed by fourier transform infrared spectroscopy technique.     

Microwave resonant and zero-field absorption study of pure and doped ferrite nanoparticles

Microwave absorption was studied for magnetic nanoparticles of Fe₃O₄ (A) prepared by co-precipitation and Ni_0.35Cu_0.15Zn_0.5Fe₂O₄ (B) nanoparticles prepared by the sol-gel combustion method at different temperature. In all cases only one ferromagnetic resonance line was observed which indicated that the materials were magnetically uniform. The linewidths were large mainly because of the wide variations in particle sizes, shapes and orientations. As expected, A type nanoparticles showed no absorption at zero-field. However, B type nanoparticles exhibited a sizable loss at a zero-field and the effect increases with the increase of reaction temperature. Mechanical crushing of the sample further enhanced the absorption.     

Synthesis of Co-Cu-Zn doped Fe3O4 nanoparticles with tunable morphology and magnetic properties

Co-Cu-Zn doped Fe₃O₄ nanoparticles can be successfully synthesized using a simple method. The particles in the size range 20−400 nm with different regular shapes i.e. sphere-like, regular hexane and tetrahedron are controllably achieved by changing the metal ion concentration. Compared to pure Fe₃O₄ without dopants, Co-Cu-Zn doped Fe₃O₄ nanoparticles exhibit better microwave absorbing properties at 2−18 GHz. Among three Co-Cu-Zn doped Fe₃O₄ nanoparticles with different morphologies, tetrahedral Co-Cu-Zn doped Fe₃O₄ nanoparticles represent a better dielectric loss in high frequency range. This work is believed the first known report of Co-Cu-Zn doped Fe₃O₄ nanoparticles with tunable morphology and magnetic properties through the hydrothermal process without using any organic solvents, organic metal salts or surfactants.     

Effect of reaction condition on microstructure and properties of (NiCuZn)Fe2O4 nanoparticles synthesized via co-precipitation with ultrasonic irradiation

Nano-spinel ferrites synthesized via chemical co-precipitation method are small in size and have serious agglomeration phenomenon, which makes separation difficult in the subsequent process. Ni_0.4Cu_0.2Zn_0.4Fe₂O₄ ferrites nanoparticles were synthesized via co-precipitation assisted with ultrasonic irradiation produced by ultrasonic cleaner with 20 kHz frequency using chlorinated salts and KOH as initial materials. The effects of ultrasonic power (0, 40 W, 60 W, 80 W) and reaction temperature on the microstructure and magnetic properties of ferrite nanoparticles were investigated. The structure analyses via XRD revealed the successful formation of pure (NiCuZn)Fe₂O₄ ferrites nanospinel without any impurity. The crystallites sizes were less than 40 nm and the lattice constant was near 8.39 Å. The TEM showed ferrite particle polygonal. M−H analyses performed the saturation magnetization and coercivity of ferrite nanoparticles obtained at the reaction temperature of 25℃ were higher than at 50℃ with same power. The samples exhibited the highest values of Ms 55.67 emu/g at 25℃ and 47.77 emu/g at 50℃ for 60 W and the lowest values of Hc 71.23 Oe at 25℃ for 40 W and 52.85 Oe at 50℃ for 60 W. The squareness ratio (SQR) were found to be lower than 0.5, which revealed the single magnetic domain nature (NiCuZn)Fe₂O₄ nanoparticles. All the outcomes show the ultrasonic irradiation has positive effects on improving the microstructure and increasing magnetic properties.     

Induction heating studies of magnetite nanospheres synthesized at room temperature for magnetic hyperthermia

An investigation of the synthesis of Fe₃O₄ nanopowders by the co-precipitation method is reported from aqueous and ethanol mediums. X-ray diffraction (XRD), transmission electron microscopy (TEM) and vibrating sample magnetometer are utilized to study the effect of variation of synthesis conditions on the crystal structure, crystallite size, microstructure and magnetic properties of the formed powders. The XRD analysis showed that the crystalline Fe₃O₄ phase was formed at Fe³⁺/Fe²⁺ molar ratio 2.0 prepared at room temperature for 1 h at pH 10. The crystallite size was in the range between 8 and 11 nm. TEM micrographs showed that the particles appeared as nanospheres. Superparamagnetic nanoparticles with low coercivity and remanence magnetization were achieved. Heating properties of the nanosphere samples in an alternating magnetic field at 160 KHz were evaluated. An excellent heating efficiency for the sample prepared in ethanol medium is a result of more relaxation losses occurring due to its small particle size.