Radiolabeled ultra-small Fe₃O₄ nanoprobes for tumor-targeted multimodal imaging

In the present study, we aimed to characterize the tumor-targeting properties of ultra-small iron oxide nanoparticles (IONPs) as multimodality imaging contrast agent.

The dimeric cRGD peptides [cyclic(Cys-Arg-Gly-Asp-dSer-Cys)-Tyr-dSer-Lys-Tyr-cyclic(Cys-Arg-Gly-Asp-dSer-Cys)], which specifically targeted integrin-α_vβ₃ receptor highly overexpressed in tumor vasculature and tumor cells, were covalently conjugated onto the surface of ultra-small IONPs followed by the labeling of nuclide ¹²⁵I^- through the chloramine-T method to afford the desired ¹²⁵I-(cRGD)₂-IONPs nanoprobe.¹²⁵I-(cRGD)₂-IONPs were injected into tumor-bearing mice for magnetic resonance (MR) and single photon emission computed tomography (SPECT) multi-modality imaging of tumors.

The prepared IONPs demonstrated were very useful for T1/T2 and SPECT imaging of tumors in vivo, exhibiting a high tumor uptake of a clinically useful target-to-background ratio in a short time.

We successfully developed a novel integrin-α_vβ₃ receptor-targeted ultra-small IONPs, which could be successfully used as T1-T2-MRI/SPECT contrast agents for high-resolution and high-sensitivity of tumor imaging in vivo.