Toward theranostic nanoparticles: CB[7]-functionalized iron oxide for drug delivery and MRI

Iron oxide (gamma-Fe2O3) nanoparticles (NPs) were efficiently coated with the water soluble macrocycle cucurbit [7]uril (CB[7]) by microwave heating. Density functional theory (DFT) calculations support a binding model in which the carbonyl oxygens of CB[7] coordinate directly to surface Fe3+ ions. The modified particles (CB [7] NPs) are stable under a wide pH range (2-12) and have a transverse relaxivity, R-2, of 113 s(-1) mM(-1). Nile red (NR) dye was loaded into the cavities of the surface-adsorbed CB[7]s, and intracellular delivery of the dye to HCT116 cells was observed by confocal laser scanning microscopy. The dye-loaded particles (CB[7] NPs superset of NR) have a R-2 of 172 s(-1) mM(-1). The stability, biocompatibility, and dual purpose functionality (drug delivery and magnetic resonance imaging) of the CB[7] NPs herald the theranostic potential of this system.