Gadolinium embedded iron oxide nanoclusters as T1–T2 dual-modal MRI-visible vectors for safe and efficient siRNA delivery

This report illustrates a new strategy of designing a T1–T2 dual-modal magnetic resonance imaging (MRI)-visible vector for siRNA delivery and MRI. Hydrophobic gadolinium embedded iron oxide (GdIO) nanocrystals are self-assembled into nanoclusters in the water phase with the help of stearic acid modified low molecular weight polyethylenimine (stPEI). The resulting water-dispersible GdIO–stPEI nanoclusters possess good stability, monodispersity with narrow size distribution and competitive T1–T2 dual-modal MR imaging properties. The nanocomposite system is capable of binding and delivering siRNA for knockdown of a gene of interest while maintaining its magnetic properties and biocompatibility. This new gadolinium embedded iron oxide nanocluster provides an important platform for safe and efficient gene delivery with non-invasive T1–T2 dual-modal MRI monitoring capability.