(767a) Morphological and Surface Dependant Nano-Particle Behavior for Medical Imaging: Evaluation of Magnetic Nanoparticles for MRI and Gold Nanoparticles for CT-SCAN

The field of medical imaging has recently enhanced its medical potential applications based on nanotechnology; this is due in part to an extensive interest from different disciplines. Several researchers are currently focused on the development of molecular imagenology using nanoparticles as contrast media. These techniques have been outlined as the “non-invasive, quantitative and replicable imaging of targeted tissues or biological processes in vivo and ex-vivo”. The future applications of molecular imaging are expected to include: more accurate prognoses, personalized medicine, the ability to follow the effectiveness of treatments, and the early detection of many diseases such as cancer [1].

Current development on gold nanostructures is related to plasmon phenomena (e.g. Photothermal ablation) and its appeal arises from their potential use as both therapeutic agents and contrast media for several medical imaging techniques (e.g. photoacustic imaging and CT-SCAN). On the other hand, magnetic nanoparticles have been widely studied for magnetic resonance imaging MRI due to the alterations they induce in the spin–spin relaxation time when introduced into biological tissues.

The aim of this study is twofold. First, to provide experimental evidence as to how the shape of gold nanoparticles can affect the X-rays attenuation behavior. Here, this is achieved using gold nanoshells, nanorods, hollow gold nanoparticles and colloidal gold on controlled experiments from which the evolution of X-rays attenuation is determined. Second, to evaluate the effects of different surface modifications on superparamagnetic iron oxide nanoparticles (SPION´s) with the purpose of gathering information on how these modifications can alter the spin-spin relaxation time for MRI applications. The nanoparticles studied in this case include: magnetite capped with polyvinylpyrrolidone (PVP), magnetite capped with citrate, magnetite capped with an amino-silane, and core-shell magnetite-SiO2. The introduction of different chemical groups on the surface of magnetite is expected to modify the translational diffusion of water molecules to the magnetic core, therefore affecting the spin-spin relaxation time.

Nanoparticles are characterized by Transmission Electron Microscopy (TEM), Scanning Electron Microscopy (SEM), Dynamic Light Scattering, Zeta potential, Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD) and UV-VIS-NIR spectroscopy. Their properties such as X-ray attenuation and spin-spin relaxation time are measured in commercial medical devices for CT-SCAN tomography and MRI. 

Keywords: Shape effects, surface effects, nanoparticle based biomedical imagenology, magnetic nanoparticles, gold nanoparticles, SPION´S.

References:

[1] Thorek D. J., Chen A. K., Czupryna J., Tsourkas A.; Superparamagnetic Iron Oxide Nanoparticle Probes for Molecular Imaging, Annals of Biomedical Engineering 34 1 ,p. 23-38 (2006).