Development of dual modality lanthanide-doped magnetite nanoparticles for potential biomedical imaging

In recent years, the application of iron oxide nanoparticles for a myriad of research fields has opened many new avenues for possible biomedical applications. The potential to combine the paramagnetic property of iron oxide nanoparticles with the luminescence properties of a lanthanide metal would be an important development in the biomedical imaging of tumors. With the ability to intravenously administer dual functionality nanoparticles such as these, a medical team could have both a magnetic resonance image, (MRI), due to the T2 relaxation of magnetite, along with a fluorescent image through the use of laparoscopic techniques. Both images could then be overlaid to give a more comprehensive and accurate understanding of the affected biological area during surgery or treatment. The purpose of this research was to develop super-paramagnetic magnetite nanoparticles incorporated with a lanthanide metal ion to create dual functionality nanoparticles possessing both paramagnetic properties and monochromatic luminescent properties. The nanoparticles were synthesized using a high temperature-based thermal decomposition method or a low temperature-based co-precipitation method. Once the nanoparticles were synthesized, they were made available for coordination with an organic chromophore to provide the means for luminescence. A chromophore's, or sensitizer's purpose is to perform ligand-to-metal energy transfer. For europium, coordinated with the chromophore chosen this light is a bright red, with a wavelength of 614 nm. To optimize the ratio of iron oxide to europium, various theoretical europium doping values for the magnetite nanoparticle were tested. The amount of surface coordination with the chromophore was also tested with each incorporation percentage to determine the optimal light emission for each variance. A third method was developed for synthesizing magnetite nanoparticles. In this case, making core-shell, magnetite cores with a europium shell, nanoparticles. The purpose was to compare europium-doped iron oxide nanoparticles with those surface coated with europium. The same chromophore employed for the europium doped nanoparticles was again used to provide a means for luminescence. Theoretical doping levels of europium to iron oxide for this project were 16:84, 20:80, 30:70, and 40:60 europium to iron oxide for each doped nanoparticle synthesis. The thermal decomposition method being the most efficient at doping with values for theoretical 40:60 europium to iron oxide, and actual doping was found to be 39.56:60.44. Varying amounts of TTA [thenoyltrifluoroactonate] for surface coordination will vary from 16 mg TTA/ 75 mg nanoparticles. This research found low quantum yields for all synthesized nanoparticles, with the highest quantum yield value of 1.8 +/- 0.013 %.