A new method for preparation of magnetite from iron oxyhydroxide or iron oxide and ferrous salt in aqueous solution

In this study, a new method is proposed for the preparation of Fe₃O₄ from iron oxyhydroxides (goethite, akaganeite, lepidocrocite, feroxyhyte and ferrihydrite) or iron oxide (hematite) and ferrous salt in aqueous solution. The product is magnetite with various particle sizes. Products are characterized by X-ray powder diffraction, IR spectra and vibrating sample magnetometery.     

Size-controlled synthesis of superparamagnetic iron oxide nanoparticles and their surface coating by gold for biomedical applications

The size mono-dispersity, saturation magnetization, and surface chemistry of magnetic nanoparticles (NPs) are recognized as critical factors for efficient biomedical applications. Here, we performed modified water-in-oil inverse nano-emulsion procedure for preparation of stable colloidal superparamagnetic iron oxide NPs (SPIONs) with high saturation magnetization. To achieve mono-dispersed SPIONs, optimization process was probed on several important factors including molar ratio of iron salts [Fe³⁺ and Fe²⁺], the concentration of ammonium hydroxide as reducing agent, and molar ratio of water to surfactant. The biocompatibility of the obtained NPs, at various concentrations, was evaluated via MTT (3-(4, 5-dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide) assay and the results showed that the NPs were non-toxic at concentrations <0.1 mg/mL. Surface functionalization was performed by conformal coating of the NPs with a thin shell of gold (∼4 nm) through chemical reduction of attached gold salts at the surface of the SPIONs. The Fe₃O₄ core/Au shell particles demonstrate strong plasmon resonance absorption and can be separated from solution using an external magnetic field. Experimental data from both physical and chemical determinations of the changes in particle size, surface plasmon resonance optical band, phase components, core–shell surface composition, and magnetic properties have confirmed the formation of the mono-dispersed core–shell nanostructure.     

Magnetic resonance imaging with superparamagnetic iron oxide particles for the detection of myocardial reperfusion

The effect of superparamagnetic iron oxide particles on magnetic resonance myocardial signal intensity was examined in order to define the ability of this agent to identify normal, ischemic, and reperfused myocardium. Data were obtained from 6 normal rats (group 1) and from 6 heterotopic isogenic rat heart transplants (group 2) at 4.7 T with a multislice spin-echo sequence. Images were acquired in (a) normal rats before and after the infusion of 36 μmol Fe/kg of AMI-25 (group 1) and (b) rat heart transplants during control, global myocardial ischemia (before and after the injection of 72 μmol Fe/kg of AMI-25), and following reperfusion (group 2). Myocardial signal intensity decreased by 36 ± 4%, p < 0.001, following contrast infusion in normal hearts (group 1). The intensity remained constant in the rat heart transplants (group 2) during coronary occlusion, both before and after the infusion of AMI-25 and decreased by 61 ± 7%, p < 0.001, upon reperfusion. The larger effect of AMI-25 in reperfused as compared to normal myocardium suggests the presence of ischemia-induced hyperemia. There was no significant difference (analysis of variance) among intensities from different myocardial regions in either group at any stage of the experiment. We conclude that the use of AMI-25 permits identification of normal, ischemic, and reperfused myocardium and may therefore be helpful for the early detection of reperfusion following thrombolytic therapy for acute myocardial infarction.