Rapid Size- Controlled Synthesis of Dextran-Coated, Copper-Doped Iron Oxide Nanoparticles

Development of dual modality probes enabled for magnetic resonance imaging (MRI) and positron emission tomography (PET) has been on the rise in recent years due to the potential for these probes to facilitate combining the complementary high resolution of MRI and the high sensitivity of PET. The efficient synthesis of multimodal probes that include the radiolabels for PET can be hindered due to prolonged reaction times during radioisotope incorporation, and the resulting decay of the radiolabel. Along with a time-efficient synthesis, one also needs an optimal synthesis that yields products in a desirable size range (between 20-100 nm) to increase blood retention time. In this work, we describe a novel, rapid, microwave-based synthesis of dextran-coated iron oxide nanoparticles doped with copper (DIO/Cu). Traditional methods for synthesizing dextran-coated iron oxide particles require refluxing for 2 hours and result in approximately 50 nm particles. We demonstrate that microwave synthesis can produce 50 nm nanoparticles in 5 minutes of heating. We discuss the various parameters used in the microwave synthesis protocol to vary the size distribution of DIO/Cu, and demonstrate the successful incorporation of copper into these particles with the aim of future use for rapid 64Cu incorporation.