Comparative study of ferrofluids based on dextran-coated iron oxide and metal nanoparticles for contrast agents in magnetic resonance imaging

Abstract

Colloidal suspensions of iron oxide and metal iron nanoparticles prepared by laser pyrolysis have been obtained by coating the particles with dextran in an aqueous media giving rise to biocompatible ferrofluids. The structural characteristics of the powders and the size of the particles and the aggregates in the colloidal suspensions have been analysed and correlated with the magnetic properties of both solids and fluids. For the first time, to our knowledge, a stable ferrofluid based on metal particles (<10 nm) has been obtained with aggregate sizes of nm. In comparison to iron oxide based products, this material exhibits higher saturation magnetization (45 emu g−1) and susceptibilities (4000 emu/g T). In addition, the nuclear magnetic resonance response of the ferrofluids has been measured in order to gain information about the influence of the crystallochemical and magnetic properties on their relaxation behaviour. The main parameter affected by the presence of the magnetic nanoparticles is the transversal relaxation time T2 and the corresponding relaxivity R2 value that is of the order of 400 (mmol/l)−1 s−1. It has been shown that R2 value increases not only by using iron metal instead of iron oxide but also by increasing the crystal size of the particles. From this study an evaluation of the possibilities of these materials as contrast agents for magnetic resonance imaging has been made.

Finite size effects on the electrical properties of sol–gel synthesized CoFe2O4powders: deviation from Maxwell–Wagner theory and evidence of surface polarization effects

“…Below a critical size, magnetic particles become single domain in contrast to the multidomain structure of the bulk magnetic materials and these nanomagnetic materials exhibit unique phenomena such as superparamagnetism [2], quantum tunnelling of magnetization [3], etc. Owing to the unique physical properties, magnetic nanoparticles have potential applications in diverse areas such as information storage [4], colour imaging [5], ferrofluids [6] and magnetic refrigeration [7].…”

Activation of Schwann cells in vitro by magnetic nanocomposites via applied magnetic field

“…[22][23][24] A recent study has reported that MNP-bound BDNF can transmigrate across the blood brain barrier using an in vitro blood brain barrier model and subsequently exert the role of BDNF in neuroprotection, which represents an extensive application of MNPs with additional molecular factors. 25 In addition, chitosan and glycerophosphate are biodegradable, mucoadhesive, and nontoxic polymers, which show good biocompatibility for neuron survival and adherence.…”

Folate-targeted polymeric micelles loaded with ultrasmall superparamagnetic iron oxide: combined small size and high MRI sensitivity

“…For the PEG-PCL-SPION aqueous dispersions, the mobility of water molecules in the diffusing layer is restricted because of hydrogen bonding between the water molecules and the hydrophilic chains of the PEG blocks, resulting in a large amount of bound water, which should be one of the reasons for the high T 2 relaxivities of PEG-PCL-SPIONs. Note that the r 1 , respectively, corresponding to an r 2 /r 1 value of 11.3 at 1.5T in the manufacturer's product summary. Therefore the high r 2 /r 1 value (herein 78) makes PEG-PCL-SPIONs a very promising T 2 contrast agent.…”

“…1 Targeted delivery of contrast agents is a highly desirable strategy for simultaneously enhancing contrast effect and reducing side effects and toxicity. This technique is extremely useful for detecting early signs of diseases.…”