Synthesis of ferrofluid with magnetic nanoparticles by sonochemical method for MRI contrast agent

https://doi.org/10.1016/j.jmmm.2004.11.093Get rights and content

Abstract

Superparamagnetic iron oxide nanoparticles (SPIO) having high magnetization (83 emu/g) and crystallinity were synthesized by using a sonochemical method. Ferrofluids from these nanoparticles coated with oleic acid as a surfactant were prepared for magnetic resonance imaging (MRI) contrast agent. The coated SPIO could be easily dispersed in chitosan, and the hydrodynamic diameter of the coated SPIO in the chitosan solution was estimated to be 65 nm. The ferrofluids of various concentrations did not agglomerate for 30 days, indicating their good stability. The T1- and T2-weighted MR images of these ferrofluids were obtained and the MRI image contrasts were similar to those of Resovist®.

Introduction

Superparamagnetic iron oxide nanoparticles (SPIO) are of great interest for several clinical applications: they were recently introduced as a suitable material for drug-targeting [1], hyperthermia [2], embolotherapy [3], and magnetic resonance imaging agent [4], [5]. Especially for magnetic resonance imaging (MRI) contrast agents, the SPIO as well as gadolinium or manganese salts are by far the most common. Superparamagnetic contrast agents have an advantage of producing an enhanced proton relaxation in MRI in comparison with paramagnetic ones. Consequently, less amount of SPIO agent was needed to dose into the human body than paramagnetic. To apply the magnetic fluids to MRI contrast agent, the SPIO should be dispersed in a biocompatible and biodegradable carrier.

In this study, we synthesized SPIO by a sonochemical method and compared with those by a coprecipitation. From the SPIO by the sonochemical method, we synthesized ferrofluids for MRI contrast agent by coating them with oleic acid as a surfactant and then dispersed them in the chitosan, which is a suitable carrier for bioapplications.

We have characterized the nanoparticles by using an X-ray diffraction (XRD), a superconducting quantum interference device (SQUID), and a transmission electron microscope (TEM). The coated particles were analyzed by photon correlation spectroscopy (PCS) to measure the particle size. The MR images of the ferrofluids were obtained and compared with the images of Resovist®. Resovist® is a commercially available contrast agent for MRI from Schering and consists of SPIO nanoparticles coated with carboxydextrane.

Section snippets

Experimental

All the chemicals were of reagent grade used without further purification. Ferric chloride hexahydrate (FeCl3·6H2O), ferrous chloride tetrahydrate (FeCl2·4H2O), and oleic acid (C18H34O2) were purchased from Aldrich, while ammonium hydroxide (NH4OH) and sodium hydroxide (NaOH) from Junsei.

A mixed solution of 0.15 M FeCl2 (50 ml, 7.5 mM) and 0.30 M FeCl3 (50 ml, 15.0 mM) was prepared. As soon as ultrasonic waves were irradiated (ULSSO HITECH Co. LTD, Model ULH700S, 10 mm, Ti horn, 20 kHz) to the mixture

Results and discussion

The result of XRD showed that the ferrite nanoparticles obtained by the sonochemical and coprecipitation method had spinel magnetite crystal structure (Fig. 1). The magnetite nanoparticles by the sonochemical method showed, however, higher crystallinity than the particles by the coprecipitation. The magnetite by the sonochemical method was spherical and had the average diameter of about 15 nm as shown in Fig. 2. Considering their size, shape and crystallinity, the SPIO by sonochemistry were

Conclusions

Superparamagnetic iron oxide nanoparticles (SPIO) were synthesized by the sonochemical method. These spherical particles of about 15 nm in diameter showed superparamagnetic behavior. We confirmed these SPIO could be well dispersed in chitosan to make ferrofluids. And the ferrofluids exhibited the enhancement of MRI contrasts comparable to Resovist® in vitro. We are carrying out experimentation in vivo. Still much work remains to be done to make the ferrofluids reliable for the clinical

References (5)

  • A. Jordan et al.

    J. Magn. Magn. Mater.

    (1999)
  • J. Liu et al.

    J. Magn. Magn. Mater.

    (2001)
There are more references available in the full text version of this article.

Cited by (0)

View full text