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.