AS1411 aptamer-conjugated Gd₂O₃: Eu nanoparticles for target-specific computed tomography/magnetic resonance/fluorescence molecular imaging

Europium-doped gadolinium oxide (Gd₂O₃: Eu) nanoparticles have been synthesized, and then their surfaces have been conjugated with nucleolintargeted AS1411 aptamer to form functionalized target-specific Gd₂O₃: Eu nanoparticles (A-GdO: Eu nanoparticles). The A-GdO: Eu nanoparticles present strong fluorescence in the visible range, high magnetic susceptibility, X-ray attenuation and good biocompatibility. The A-GdO: Eu nanoparticles have been applied to test molecular expression of nucleolin highly expressed CL1-5 lung cancer cells under a confocal microscope. Fluorescence imaging clearly reveals that the nanoparticles can be applied as fluorescent tags for cancer-targeting molecular imaging. Furthermore, taking together their excellent T₁ contrast and strong computed tomography (CT) signal, the A-GdO: Eu nanoparticles demonstrate a great capability for use as a dual modality contrast agent for CT and magnetic resonance (MR) molecular imaging. Animal experiments also show that the A-GdO: Eu nanoparticles are able to contrast the tissues of BALB/c mice using CT modality. Moreover, the obvious red fluorescence of A-GdO: Eu nanoparticles can be visualized in a tumor by the naked eye. Overall, our results demonstrate that the A-GdO: Eu nanoparticles can not only serve as new medical contrast agents but also as intraoperative fluorescence imaging probes for guided surgery in the near future.