Ultrasmall Water-Soluble and Biocompatible Magnetic Iron Oxide Nanopartides as Positive and Negative Dual Contrast Agents

摘要

Monodispersed water-soluble and biocompatible ultrasmall magnetic iron oxide nanopartides (UMIONs, D = 3.3 ± 0.5 nm) generated from a high-temperature coprecipitation route are successfully used as efficient positive and negative dual contrast agents of magnetic resonance imaging (MRI). Their longitudinal relaxivity at 4.7 T (r_1 = 8.3 mM~(-1) s~(-1)) is larger than that of clinically used T_1-positive agent Cd-DTPA (r_1 = 4.8 mM~(-1) s~(-1)), and three times that of commercial contrast agent SHU-555C (r_1 = 2.9 mM~(-1) s~(-1)). The transversal relaxivity (r_2 = 35.1 mM~(-1) s~(-1)) is six times that of Cd-DTPA (r_2 = 5.3 mM~(-1) s~(-1)), half of SHU-555C (r_2 = 69 mM~(-1) s~(-1)). The in vivo results show that the liver signal from T_1-weighted MRI is positively enhanced 26%, and then negatively decreased 20% after injection of the iron oxide nanopartides, which is stronger than those obtained from Cd-DTPA (<10%) using the same dosage. The kidney signal is positively enhanced up to 35%, similar to that obtained from Cd-DTPA. Under T_2-weighted conditions, the liver signal is negatively enhanced ≌70%, which is significantly higher than that from Cd-DTPA (≌6%). These results demonstrate the great potential of the UMIONs in dual contrast agents, especially as an alternative to Cd-based positive contrast agents, which have risks of inducing side effects in patients.