Hollow Silica Nanospheres for Magnetic Resonance Imaging Application

In recent years, magnetic resonance imaging (MRI) is one of the paramount techniques in diagnostic and biomedical research, providing a nondestructive tool in examining soft tissues. Because of the relatively low sensitivity, contrast agents are often used in MRI diagnoses. Contrast agents can be divided into two groups: positive contrast agents and negative contrast agents. Positive contrast agents are mostly paramagnetic transition metals like Gd3+ ion, however, the free Gd3+ ion has been shown to be toxic both in vitro and in vivo studies. Therefore, chelation of Gd3+ ion is a way to avoid the toxicity for in vivo use.
In first section, we synthesized GdPO4@SiO2-PEG500 nanoparticles based on the modified StÖber method.. By varying the concentration of NH4H2PO4, we obtained the GdPO4@SiO2 nanoparticles and investigate the effect on the relaxivities. The second section, we developed a water-in-oil (W/O) approach to incorporate PVP-stabilized gadolinium oxide nanoparticles in hollow silica nanospheres. Gadolinium oxide particles were synthesized by thermal decomposition method and then ligand exchange with PVP. By varying the concentration of PVP-stabilized Gd2O3 nanoparticles encapsulated in hollow silica nanosphere, we also investigated the effect on the relaxivities. These nanoparticles were characterized by TEM, relaxation measurements, DLS, XRD, FTIR and ICP-MS.