Superparamagnetic iron oxide nanoparticles (SPIO) are widely used in medicine as MRI contrast agents and plays important role in drug delivery systems. Doxorubicine is known as important medicine in tumor therapy. Nanocomplexes of superparamamgnetic iron oxide/doxorubicine (SPIO/DOX) have ability to accumulate in the tumor area, so they are well suited to use in monitoring of tumor treatment by magnetic resonance imaging (MRI).

Dispersion of SPIO/DOX complexes in water and saline were investigated using Nuclear Magnetic Resonance (NMR) techniques: relaxation and imaging. Studies of proton relaxation have been performed at three magnetic fields intensities 0.4T, 4.7T and 9.4T. Relaxation times, T1 and T2 have been measured (using Inversion-recovery and CPMG pulse sequences, respectively)  for samples of different concentration (mM) of investigated nanoparticles in water and physiological saline. Relaxivity parameters r1 and r2 were calculated for measured dispersion series for each value of magnetic field.

In all studied values of transverse relaxivity (r2) are significantly higher than longitudinal relaxivities (r1). Furthermore, values of r2 are comparable in aqueous and physiological saline solutions across the series and persist above 100 mM-1 sec-1. Also it should be noted that values of r1 increase with decreasing magnetic field. Obtained results allow to conclude that SPIO/DOX can be classified as effective T2 contrast agent in wide range of magnetic fields commonly used  in medical diagnosis. Aforementioned complex can also be used as T1 contrast agent in human diagnosis up to magnetic fields of 1T.

Series of T2-weighted MRI images of solution of SPIO/DOX injected into agarose gel were obtained at 9.4T using Fast Spin Echo sequence (TR = 2s, TE = 20ms). The successive images were used as a monitor of contrast area changes in function of time after injection. Results confirmed that investigated particles are efficient T2 contrast agent and have ability to easily spreading by diffusion in environment with tissue-like density.

Acknowledgements

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