SYNTHESIS AND CHARACTERIZATIONS OF NANOSTRUCTURED MAGNETIC MATERIALS FOR MRI T1 CONTRAST AGENTS
The synthesis of magnetic nanomaterials (Gd2O3, Mn-doped ZnS and iron oxide with different size and morphologies) for potential applications as MRI T1 contrast agents was studied. These nanoparticles were characterized by using TEM, XRD, FTIR, Zeta potential, DTA/TGA and XPS. (1) Gd2O3 nanoparticles were synthesized with three different morphologies. Four synthetic factors were investigated, i.e. temperature, time, solvent and surfactant. It was found that the degree of Gd2O3 crystallization was greatly influenced by temperature. Sphere shape was selected as the optimized structure to obtain the best paramagnetic performance. Yb:Er co-doped Gd2O3 nanospheres were then successfully synthesised using thermal decomposition method. They were equiaxed in shape, and exhibited T1 effect with r1=1.529s-1mM-1. (2) A facile method for fabricating Gd2O3 nanoclusters (GNCs) was demonstrated with enhanced T1 effect. It was found that such protection did not only allow the Gd2O3 to be applied in wide pH range, but also avoided further aggregation. A relationship was demonstrated to exist between Gd2O3 loading and r1 per single cluster. The GNCs possessed high r1 values (up to 7.948 s-1mM-1 [Gd]) and low r2/r1 (down to 1.04). For all of the Gd loadings, polymer nanogel platform materials provided higher longitudinal relaxivity than the monodispersed individual Gd2O3. Hence, the GNCs were shown to be more effective as contrast agents than Gd2O3 -based counterparts. In vitro test was performed with cell lines, and clear T1-weight images were obtained. Thus, the POMA-g-PEG assisted GNCs were demonstrated to be potentially useful for magnetic-assisted delivery systems. (3) Dual modal contrast agent was successfully synthesized based on Mn-doped ZnS nanoparticles on graphene oxide (ZMGO). The ZMGO nanocomposites with three different emission colors, namely, blue, white and red, were synthesized. The average sizes of the ZMGO nanocomposites were all below 130 nm range, which facilitated VI various potential bio-applications especially in vivo bio-applications. The nanocomposites combined the MRI and fluorescent labels, and graphene oxide (GO) offered the nanocomposites superior water solubility due to the oxygenated functional groups on the edges of graphene. Mn-doping concentration conferred the nanocomposites with tunable emissions. After the hybridization, the ZMGO nanocomposites exhibited bright emissions under UV irradiation, as well as promising water solubility. After the PEGylation, the nanocomposites prominently improved the colloidal stability in PBS solution. Finally the as-obtained ZMGO-PEG nanocomposites maintained the bright fluorescence and were successfully used for in vitro imaging application. Moreover, the r1 value was 0.616 s-1mM-1, which was significant to offer a brightness in T1 imaging, Hence, it was shown that the nanocomposites combining fluorescent and MR contrast agent were promising candidates for biomedical cellular imaging application. (4) A facile approach to synthesize ultra small iron oxide (USIO) that could be used as contrast agent in MRI was studied. GO was shown to be a viable substrate for growing USIO, resulting in USIO-GO composite, which could combine two complementary techniques, namely, T1 MRI and optical fluorescence imaging. An energy transfer mechanism was identified from USIO to GO that resulted in its photoluminescence. The nanocomposite showed good cell viability with different cancer cell lines.
magnetic materials,MRI, nanomaterials, fluorescent cell imaging, T1 imaging, contrast agents
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