Multifunctional Dendrimer-Entrapped Gold Nanoparticles Modified with RGD Peptide for Targeted Computed Tomography/Magnetic Resonance Dual-Modal Imaging of Tumors

We report the use of multifunctional dendrimer-entrapped gold nanoparticles (Au DENPs) loaded with gadolinium (Gd) chelator/Gd­(III) complexes and surface-modified with thiolated cyclo­(Arg-Gly-Asp-Phe-Lys­(mpa)) (RGD) peptide for targeted dual-mode computed tomography (CT)/magnetic resonance (MR) imaging of small tumors. In this study, amine-terminated generation 5 poly­(amidoamine) dendrimers were used as a nanoplatform to be covalently modified with Gd chelator, RGD via a polyethylene glycol (PEG) spacer, and PEG monomethyl ether. Then the multifunctional dendrimers were used as templates to entrap gold nanoparticles, followed by chelating Gd­(III) ions and acetylation of the remaining dendrimer terminal amines. The thus-formed multifunctional Au DENPs (in short, Gd–Au DENPs-RGD) were characterized via different techniques. We show that the multifunctional Au DENPs with a Au core size of 3.8 nm are water-dispersible, stable under different pH (5–8) and temperature conditions (4–50 °C), and noncytotoxic at a Au concentration up to 100 μM. With the displayed X-ray attenuation property and the r₁ relaxivity (2.643 mM^–1 s^–1), the developed Gd–Au DENPs-RGD are able to be used as a dual-mode nanoprobe for targeted CT/MR imaging of an α_vβ₃ integrin-overexpressing xenografted small tumor model in vivo via RGD-mediated active targeting pathway. The developed multifunctional Gd–Au DENPs-RGD may be used as a promising dual-mode nanoprobe for targeted CT/MR imaging of different types of α_vβ₃ integrin-overexpressing cancer.