Eur. Phys. J. Appl. Phys. 55, 10401 (2011)
https://doi.org/10.1051/epjap/2011100244

The effect of coating of Fe₃O₄/silica core/shell nanoparticles on T₂ relaxation time at 9.4 T

¹ Department of Clinical Neurosciences, University of Calgary, 1403 – 29th Street NW, Calgary, T2N 4N1, Alberta, Canada
² Institute of Nuclear Physics, Polish Academy of Sciences, Radzikowskiego 152, 31-342 Krakow, Malopolska, Poland
³ Institute for Biodiagnostics (West), National Research Council of Canada, 3330 Hospital Dr. NW Calgary, T2N 4N1, Alberta, Canada
⁴ Suzhou Institute of Nano-tech and Nano-bionics, Chinese Academy of Sciences, 398 Ruoshui Rd, Duhu Lake Higher Education District, Suzhou Industrial Park, Suzhou, 215125, P.R. China
⁵ Industrial Material Institute, National Research Council of Canada, 75 de Mortagne Boulevard, Boucherville, J4B 6Y4, Québec, Canada
⁶ Énergie, Matériaux et Télécommunications, Institut national de la recherche scientifique, Université du Québec, 1650 boulevard Lionel-Boulet, Varnennes, J3X 1S2, Québec, Canada

^a e-mail: boguslaw.tomanek@nrc-cnrc.gc.ca

Received: 9 June 2010
Revised: 25 January 2011
Accepted: 16 February 2011
Published online: 21 July 2011

Abstract

Magnetic Resonance Imaging (MRI) that provides superior soft tissue contrast is commonly used for diagnosis of many diseases. However specificity of MRI cancer diagnosis can be further increased by application of target contrast agents comprising superparamagnetic nanoparticles (NPs) synthesised with biological objects, which deliver the contrast to the specific cancer cells. These superparamagnetic NPs shorten T₂ relaxation time thus change contrast to noise ratio for tumor tissues. Therefore the impact of Fe₃O₄ size and silica coating for Fe₃O₄/silica core/shell superparamagnetic nanoparticles (NPs) on T₂ relaxation time was studied at 9.4 T. The magnetic resonance imaging (MRI) studies were performed using homogenous agar solution of NPs. Naked Fe₃O₄NPs with a mean core diameter of 10.0 ± 1.3 (mean ± SD), 15.0 ± 2.5 and 20.0 ± 0.9 nm were analyzed. Silica coated Fe₃O₄ NPs with core size of 10.0 ± 1.3 nm and the shell thickness of 16.7 ± 1.8, 25.3 ± 2.7 and 33.9 ± 4.0 nm were also investigated. The T₂ values of agar solutions with different NPs were calculated using a single slice multi echo method and single exponential fitting of the echo train. The measurements showed linear correlation between T₂ and Fe₃O₄ core diameter as well as shell thickness. Silica coating, while improving functionalization and potentially reducing toxicity of NPs, decreases the impact of the magnetic core on T₂, thus decreasing MRI contrast efficacy.