Superparamagnetic Iron Oxide Nanoparticles as MRI …

Sun, “Static and dynamic magnetic properties of composite Au-Fe3O4 nanoparticles”, IEEE Trans.

Takashi Ogi HP - Hiroshima University

In conclusion, we have developed a facile, one-pot hydrothermal method for the synthesis of magnetite nanoparticles with a core-shell structure. The magnetite nanoparticles we obtained have monodispersity, no agglomeration, and a diameter of 50–60 nm. The magnetite nanoparticles also exhibited superparamagnetic properties, high saturation magnetization (65 emu/g), and were highly water soluble, which makes them an ideal candidate for drug delivery. The crystal growth kinetics study discovered a correlation among reaction time, crystal size, crystallinity, and magnetization saturation. A longer reaction time will increase the crystals’ sizes and crystallinity. In addition, the value of the saturation magnetization grew with increasing crystallinity. The magnetite-crystal growth data can be fitted to an Ostwald ripening model with the growth being controlled by the dissolution of the surface reaction (n?4), with a percentage error of 2.53%.

Synthesis and Characterization of Superparamagnetic Fe3O4@SiO2 Nanoparticles.

International Journal of Nanomedicine - Dove Press

Magnetite nanoparticles (Fe3O4) are a type of magnetic particle with huge potential for application as a drug carrier due to their excellent superparamagnetic, biocompatible, and easily modified surface properties. One characteristic of nanoparticles is that they can be controlled by studying the evolution of crystal growth. The purpose of this research is to study the evolution of magnetite-crystal growth and determine the crystal growth kinetics using the Ostwald ripening model. Magnetite nanoparticles were synthesized from FeCl3, citrate, urea, and polyethylene glycol using the hydrothermal method at 220oC for times ranging from 1–12 hours. The characterizations using X-ray diffraction (XRD) indicated that the magnetite began to form after 3 hours synthesis. The crystallinity and crystal size of the magnetite increased with the reaction time. The diameter size of the magnetite crystals was in the range of 10–29 nm. The characterizations using a transmission electron microscope (TEM) showed that magnetite nanoparticles had a relatively uniform size and were not agglomerated. The core-shell nanoparticles were obtained after 3 hours synthesis and had a diameter of 60 nm, whereas the irregular-shaped nanoparticles were obtained in 12 hours and had a diameter of 50 nm. The characterizations using a vibrating sample magnetometer (VSM) revealed that magnetite nanoparticles have superparamagnetic properties. The magnetization saturation (Ms) value was proportional to the degree of crystallinity. The magnetite-crystal growth data can be fitted to an Ostwald ripening model with the growth controlled by the dissolution of the surface reaction (n?4).

In conclusion, we have developed a facile, one-pot hydrothermal method for the synthesis of magnetite nanoparticles with a core-shell structure. The magnetite nanoparticles we obtained have monodispersity, no agglomeration, and a diameter of 50–60 nm. The magnetite nanoparticles also exhibited superparamagnetic properties, high saturation magnetization (65 emu/g), and were highly water soluble, which makes them an ideal candidate for drug delivery. The crystal growth kinetics study discovered a correlation among reaction time, crystal size, crystallinity, and magnetization saturation. A longer reaction time will increase the crystals’ sizes and crystallinity. In addition, the value of the saturation magnetization grew with increasing crystallinity. The magnetite-crystal growth data can be fitted to an Ostwald ripening model with the growth being controlled by the dissolution of the surface reaction (n?4), with a percentage error of 2.53%.


Magnetic Properties of Nanoparticles

Medarova . synthesized a breast tumor-targeted nanodrug designed to specifically shuttle siRNA to human breast cancer while simultaneously allowing for the noninvasive monitoring of the siRNA delivery process []. The nanodrug consisted of SPIONs for MRI monitoring, Cy5.5 fluorescence dye for near-infrared (IR) optical imaging, and siRNA to target the tumor-specific antiapoptotic gene . Magnetic iron oxide nanoparticles are extensively used as multimodal imaging probes in combination with optical fluorescence dyes to obtain the benefits of optical imaging, such as rapid screening and high sensitivity. Because tumor-associated underglycosylated mucin-1 (uMUC-1) antigen is overexpressed in >90% of breast cancers and in >50% of all cancers in humans [], researchers have decorated nanodrugs with uMUC-1-targeting EPPT synthetic peptides for selective tumor targeting. As shown in Figure A, amine-functionalized superparamagnetic iron oxide nanoparticles with a cross-linked dextran coating (MN) have been prepared, and a Cy5.5 dye was conjugated to the surface of nanoparticles to produce MN-Cy5.5. Subsequently, thiol-modified, FITC-labeled EPPT peptides and siRNA were coupled to MN-Cy5.5 via a heterofunctional cross-linker, -succinimidyl 3-(2-pyridyldithio) propionate (SPDP). The resulting therapeutic and diagnostic nanodrug (MN-EPPT-siBIRC5) exhibited superparamagnetic and fluorescence properties. After intravenous injection of the nanodrugs into mice with BT-20 breast tumors, the tumors were clearly imaged, as verified simultaneously by T2 MRI and near-IR optical imaging (Figure B). Systemic administration of the nanodrug once a week over 2 weeks induced considerable levels of necrosis and apoptosis in the tumors as a result of the siBIRC5-mediated inhibition of the antiapoptotic survivin protooncogene, translating into a significant decrease in tumor growth rate (Figure C). This tumor-targeted, imaging-capable nanodrug highlights the potential of MRI-guided tumor treatment, which can be used to quantify changes in the tumor volume over the treatment schedule as well as to guide selection of an optimal treatment time course.

Effective approach for the synthesis of monodisperse magnetic ..

Highly monodisperse sodium citrate-coated spherical silver nanoparticles (Ag NPs) with controlled sizes ranging from 10 to 200 nm have been synthesized by following a kinetically controlled seeded-growth approach via the reduction of silver nitrate by the combination of two chemical reducing agents: sodium citrate and tannic acid. The use of traces of tannic acid is fundamental in the synthesis of silver seeds, with an unprecedented (nanometric resolution) narrow size distribution that becomes even narrower, by size focusing, during the growth process. The homogeneous growth of Ag seeds is kinetically controlled by adjusting reaction parameters: concentrations of reducing agents, temperature, silver precursor to seed ratio, and pH. This method produces long-term stable aqueous colloidal dispersions of Ag NPs with narrow size distributions, relatively high concentrations (up to 6 × 1012 NPs/mL), and, more important, readily accessible surfaces. This was proved by studying the catalytic properties of as-synthesized Ag NPs using the reduction of Rhodamine B (RhB) by sodium borohydride as a model reaction system. As a result, we show the ability of citrate-stabilized Ag NPs to act as very efficient catalysts for the degradation of RhB while the coating with a polyvinylpyrrolidone (PVP) layer dramatically decreased the reaction rate.